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Influenza

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Influenza

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Influenza
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Disease Issues
How serious a problem is influenza in the U.S.?
Influenza is the most frequent cause of death from a vaccine-preventable disease in the United States after COVID-19. Rates of infection from seasonal influenza are highest among children, but the risks for complications, hospitalizations, and deaths are higher among adults age 65 years and older, children younger than 5 years, pregnant women, and people of any age who have medical conditions that place them at increased risk for complications from influenza.
From the 2010–11 through the 2019–20 seasons, the annual influenza-related disease burden has varied from approximately 9–45 million illnesses, 4–21 million medical visits, 140,000–810,000 hospitalizations and 12,000–61,000 deaths per year.* The number of influenza laboratory confirmed deaths in children reported to CDC has averaged 133 deaths (range 37–199) per year. This is considered an underestimate of actual pediatric deaths as some influenza-related deaths are likely not reported or recognized. For more information on the health burden of influenza, see www.cdc.gov/flu/about/burden/index.html.
* Estimates from 2017–20 are preliminary. These estimates include median estimates for all years except for 2019–20 season where the 95% confidence interval is included as the median estimate is not yet published.
What medical conditions increase the risk of severe illness from influenza?
While even healthy children and adults can get severe influenza or die from influenza and its complications, the risk of severe influenza is higher for children younger than 5 years, adults 50 years and older, pregnant women, Alaska Natives and American Indians, and residents of nursing homes or other long-term care facilities. Medical conditions that increase a person's risk of severe influenza include chronic pulmonary (including asthma), cardiovascular (excluding isolated hypertension), renal, hepatic, neurologic, hematologic, or metabolic disorders (including diabetes mellitus); immunocompromising conditions due to any cause (including but not limited to immune suppression caused by medications or HIV); extreme obesity (body mass index of >40 for adults); and the chronic use of aspirin- or salicylate-containing medications in children through age 18 (due to the risk of Reye syndrome after influenza infection).
More information about risk factors for severe influenza infection can be found at: www.cdc.gov/flu/highrisk/index.htm.
How do risk groups for severe illness from influenza and SARS-CoV-2 compare to each other?
People of all ages are susceptible to illness from both influenza and SARS-CoV-2, the virus that causes COVID-19. High risk groups for severe illness from influenza and SARS-CoV-2 are very similar. The most significant differences are that people with isolated hypertension or any degree of overweight or obesity (not just extreme obesity) are at increased risk of severe COVID-19 illness. CDC identifies people at increased risk of severe COVID as older adults, with risk increasing as age increases; and people with cancer; chronic kidney disease; chronic lung diseases; dementia and other neurologic conditions; Down syndrome; HIV infection; immunocompromised state (weakened immune system, solid organ or blood stem cell transplant); liver disease; overweight and obesity (body mass index [BMI] of 25 or higher); heart conditions such as heart failure, coronary artery disease, cardiomyopathies, or hypertension; stroke or cerebrovascular disease; sickle cell disease or thalassemia; current or former smoker; substance use disorders; type 1 and type 2 diabetes, or pregnancy and recently pregnant.
More information about risk factors for severe COVID-19 can be found at: www.cdc.gov/coronavirus/2019-ncov/need-extra-precautions/index.html.
Since influenza virus circulation was very limited during the 2020–21 influenza season, what might be expected for 2021–22 influenza season?
The timing and severity of influenza seasons are always unpredictable. Influenza viruses circulated at low levels in 2020–21 while measures to prevent the spread of COVID-19 were widely adopted, including social distancing, mask wearing, and reduction in travel. As the use of these COVID-19 mitigation measures has decreased, increases in the circulation of other non-influenza respiratory viruses have occurred. Thus, it is likely that influenza virus circulation will also increase during 2021–22. Current information on non-influenza respiratory viruses can be found at www.cdc.gov/surveillance/nrevss/index.html. Current information on influenza virus circulation can be found at www.cdc.gov/flu/weekly/index.htm.
Can influenza viruses circulate at the same time as SARS-CoV-2, the virus that causes COVID-19?
Yes. Both viruses co-circulated at the start of the COVID-19 pandemic, although the number of influenza viruses detected in the U.S. decreased substantially beginning in the spring of 2020. The extent to which SARS-CoV-2 and influenza viruses will co-circulate during this upcoming influenza is unknown, however, providers should prepare for increases in influenza as the use of prevention measures like masks, and social distancing decrease.
Where can I get information on influenza and its surveillance?
Information regarding influenza surveillance is available year-round from CDC at www.cdc.gov/flu/weekly/fluactivitysurv.htm. The full FluView surveillance report is published each Friday afternoon from October through mid-May and an abbreviated FluView report is published Mid-May through September. In addition, periodic updates about influenza are published in MMWR.
State and local health departments should be consulted regarding availability of influenza vaccine, access to vaccination programs, information about state or local influenza activity, and for reporting influenza outbreaks and receiving advice regarding their control.
Vaccine Recommendations Back to top
Please summarize what's new in the 2021–22 influenza vaccine recommendations?
Yearly influenza vaccination continues to be recommended for everyone age 6 months and older. All available influenza vaccines in the United States are now quadrivalent (containing two influenza A and two influenza B strains). The 2021–22 vaccines have been updated to include new influenza A (H3N2) and influenza A (H1N1) virus vaccine antigens. One vaccine product, Flucelvax Quadrivalent (ccIIV4, Seqirus) is now FDA-approved for children age 2 years and older (formerly approved for children age 4 years and older).
In addition, the 2021–22 recommendations discuss considerations for co-administration of influenza vaccine with a COVID-19 vaccine. Influenza vaccines and other vaccines may be administered at the same time as a COVID-19 vaccine. Guidance on COVID-19 vaccination, including coadministration with other vaccines, is available here: www.cdc.gov/vaccines/covid-19/clinical-considerations/covid-19-vaccines-us.html. If administered simultaneously, COVID-19 vaccines and influenza vaccines that might be more likely to cause a local reaction [e.g., adjuvanted inactivated influenza vaccine (aIIV4, Fluad Quadrivalent, Seqirus) or high-dose inactivated vaccine (HD-IIV4 Fluzone High-Dose Quadrivalent (Sanofi Pasteur)] should be administered in different limbs, if possible].
CDC also now recommends that providers consider influenza vaccination of pregnant people in their third trimester as soon as vaccine is available. CDC continues to recommend that children not previously vaccinated who need two doses of influenza receive their first dose as soon as possible so that they can get their second dose before the end of October. The two doses should be separated by at least 4 weeks. For non-pregnant adults, CDC continues to recommend avoiding influenza vaccination in July and August unless there is a concern that later vaccination may not be possible.
Lastly, CDC revised guidance for the contraindications and precautions for the use of Flucelvax Quadrivalent (ccIIV4) and Flublok Quadrivalent (RIV4, Sanofi Pasteur) among people with a history of a severe allergic reaction to an influenza vaccine. For ccIIV4, a history of a severe allergic reaction to a prior dose of any egg-based IIV, live attenuated vaccine (LAIV), or RIV is a precaution. For RIV4, a history of a severe allergic reaction to IIV, LAIV, or ccIIV4 is a precaution. People with precautions for receiving ccIIV4 and RIV4 should be vaccinated in a medical setting under supervision of a provider who can recognize and manage severe allergic reactions. RIV4 continues to be contraindicated for people with a prior allergic reaction to any RIV vaccine components. Similarly, ccIIV4 is contraindicated for people with a prior allergic reaction to any ccIIV components.
Who is recommended to be vaccinated against influenza?
ACIP recommends annual vaccination for all people ages 6 months and older who do not have a contraindication to influenza vaccination.
Which influenza vaccines will be available during the 2021–22 influenza season?
Multiple manufacturers are producing influenza vaccine for the U.S. market for the 2021–22 season. Inactivated influenza vaccines (IIV4) will be produced using egg-based, cell culture-based, and recombinant technologies. Live attenuated nasal spray vaccine (LAIV4, Flumist Quadrivalent; AstraZeneca) will also be available. All influenza vaccines are quadrivalent (containing four strains of influenza virus).
Influenza vaccines are not all licensed for the same age groups. ACIP does not state a preference for one influenza vaccine over another for people for whom more than one vaccine is recommended and appropriate.
IAC has a handout that summarizes each of the products available for the current influenza vaccination season at www.immunize.org/catg.d/p4072.pdf.
What are the vaccine viruses for the 2021–22 influenza season?
Vaccine viruses differ by the type of vaccine, but they are designed to protect against the same strains of circulating viruses. For the 2021–22 season, U.S. egg-based influenza vaccines (i.e., vaccines other than ccIIV4 and RIV4) will contain hemagglutinin (HA) derived from:
an influenza A/Victoria/2570/2019 (H1N1)pdm09-like virus [new];
an influenza A/Cambodia/e0826360/2020 (H3N2)-like virus [new];
an influenza B/Washington/02/2019 (Victoria lineage)-like virus; and
an influenza B/Phuket/3073/2013 (Yamagata lineage)-like virus.
For the 2021–22 season, U.S. cell culture–based inactivated (ccIIV4) and recombinant (RIV4) influenza vaccines will contain HA derived from:
an influenza A/Wisconsin/588/2019 (H1N1)pdm09-like virus [new];
an influenza A/Cambodia/e0826360/2020 (H3N2)-like virus [new];
an influenza B/Washington/02/2019 (Victoria lineage)-like virus; and
an influenza B/Phuket/3073/2013 (Yamagata lineage)-like virus.
What influenza vaccines are available for children for the 2021–22 influenza season?
Four egg-based quadrivalent inactivated influenza vaccines (IIV4s), all given as intramuscular injections, are available for children age 6 months and older:
Afluria Quadrivalent (Seqirus): 0.25 mL/dose for age 6 through 35 months; 0.5 mL/dose for age 3 years and older
Fluarix Quadrivalent (GlaxoSmithKline): 0.5 mL/dose for age 6 months and older
FluLaval Quadrivalent (GlaxoSmithKline): 0.5 mL/dose for age 6 months and older
Fluzone Quadrivalent (Sanofi Pasteur): 0.25 mL or 0.5 mL per dose for age 6 through 35 months; 0.5 mL/dose age 3 years and older
Flucelvax Quadrivalent (ccIIV4, Seqirus): 0.5 mL/dose given intramuscularly, is available for children age 2 years and older.
Flumist Quadrivalent (LAIV4, AstraZeneca): 0.2 mL administered intranasally (0.1 mL in each nostril), is available for healthy, non-pregnant children age 2 years and older.
What influenza vaccines are available for adults?
Four egg-based quadrivalent standard dose IIV vaccines (SD-IIV4s), all given as intramuscular injections, are available for adults of all ages:
Afluria Quadrivalent (Seqirus): 0.5 mL/dose
Fluarix Quadrivalent (GlaxoSmithKline): 0.5 mL/dose
FluLaval Quadrivalent (GlaxoSmithKline): 0.5 mL/dose
Fluzone Quadrivalent (Sanofi Pasteur): 0.5 mL/dose
Flublok Quadrivalent (RIV4, Sanofi Pasteur): 0.5 mL/dose given intramuscularly is available for all adults age 18 years and older.
Flumist Quadrivalent (LAIV4, AstraZeneca): 0.2 mL administered intranasally (0.1 mL in each nostril), is available for healthy, non-pregnant adults through age 49 years.
Fluzone High-Dose Quadrivalent (egg-based HD-IIV4, Sanofi Pasteur): 0.7 mL administered intramuscularly, is available for adults age 65 years and older.
Fluad Quadrivalent (egg-based aIIV4, Seqirus): 0.5 mL administered intramuscularly, is available for adults age 65 years and older.
Which children younger than age 9 years will need 2 doses of influenza vaccine in this influenza season?
Children age 6 months through 8 years should receive a second dose 4 weeks or more after the first dose 1) if they are receiving influenza vaccine for the first time, 2) if they have not received a total of at least two doses of any seasonal influenza vaccine before July 1 of the current year, or 3) if their vaccination history is unknown. The two previous doses need not have been received during the same season or consecutive seasons.
Children who are 8 years old and are recommended to receive two doses during the current season but who have a 9th birthday during the current season before receiving dose 2 should still receive dose 2.
IAC's handout titled "Guide for Determining the Number of Doses of Influenza Vaccine to Give to Children Age 6 Months Through 8 Years" provides additional guidance on this issue; it is available at www.immunize.org/catg.d/p3093.pdf.
When does CDC recommend starting influenza vaccination?
For most people, vaccination should begin in September and, ideally, be done by the end of October.
There are two groups of people for whom CDC recommends vaccination as soon as vaccine becomes available: pregnant people in the third trimester and children who need two doses of vaccine this season. Vaccination during pregnancy has been shown to reduce influenza-related hospitalizations during early infancy as a result of maternal antibodies passed to the fetus. Pregnant people in their third trimester are recommended to be vaccinated as soon as vaccine is available in order to allow time for some vaccine-induced protection to be passed to the fetus. Other pregnant people should be vaccinated by the end of October.
CDC continues to recommend that children not previously vaccinated who need two doses of influenza receive their first dose as soon as vaccine is available so that they can get their second dose before the end of October.
For nonpregnant adults, influenza vaccination during July and August should be avoided unless there is concern that later vaccination might not be possible. Early vaccination has been associated with decreased vaccine effectiveness before the end of the influenza season, particularly among older adults.
CDC recommends that influenza vaccination be offered by the end of October. This balances considerations regarding the unpredictability of timing of onset of the influenza season and concerns that vaccine-induced immunity might wane over the course of a season, particularly for older adults.
For people not vaccinated by the end of October, vaccination efforts should continue throughout the season, even after influenza activity has begun.
Should our practice consider revaccinating our high risk and older patients a second time during the year due to concerns with waning immunity?
For people who have already been fully vaccinated, revaccination later in the season is not recommended.
How late in the season can I vaccinate my patients with influenza vaccine?
Peak influenza activity generally occurs in the Northern Hemisphere in January or February. Providers should continue vaccinating patients throughout the influenza season, including into the spring months (for example, through May), as long as they have unexpired vaccine in stock and unvaccinated patients in their office.
Because influenza occurs in many areas of the world during April through September, vaccine should be given to travelers who missed vaccination in the preceding fall and winter. Another late season use of vaccine is for children younger than age 9 years who needed 2 doses of vaccine but failed to get their second dose. For each of these situations, vaccine can be given through the month of June since most injectable influenza vaccine has a June 30 expiration date.
What types of personal protective equipment do healthcare personnel need for administering vaccines in light of COVID-19?
CDC recommends that healthcare personnel administering any vaccines during COVID-19 wear surgical masks. N95 respirators are not recommended. Eye protection is recommended in areas with moderate or substantial community COVID-19 transmission; it is optional in communities with minimal or no COVID-19 transmission. Gloves are recommended when giving intranasal or oral vaccines because of the increased likelihood of coming into contact with a patient's mucous membranes and body fluids. Gloves are optional for other vaccines. Importantly, hands should be washed and gloves, when worn, should be changed between each patient. For additional details, visit the CDC web page "Interim Guidance for Routine and Influenza Immunization Services During the COVID-19 Pandemic" at www.cdc.gov/vaccines/pandemic-guidance/index.html or IAC's handout, "Protective Measures for Vaccinating during the Pandemic," available at https://immunize.org/catg.d/p2009.pdf.
May influenza vaccines be given at the same time as other vaccines, including COVID-19 vaccines?
Yes. CDC's clinical guidance for the use of COVID-19 vaccines states that any vaccine may be given on the same day or any day before or after COVID-19 vaccination, at a different anatomic site. According to the CDC's "General Best Practice Guidelines for Immunization," simultaneously administering all vaccines for which a person is eligible at the time of a visit increases the probability that a person will be fully vaccinated by the appropriate time. If administered at the same time, COVID-19 vaccines and influenza vaccines that might be more likely to cause a local reaction (aIIV4 or HD-IIV4) should be administered in separate limbs, if possible.
Because CDC guidance on COVID-19 vaccination is updated as new information emerges, periodically check the CDC website for updates to ACIP recommendations on the use of COVID-19 vaccine (www.cdc.gov/vaccines/hcp/acip-recs/vacc-specific/covid-19.html) and updates to CDC's interim clinical guidance for the use of COVID-19 vaccines (www.cdc.gov/vaccines/covid-19/clinical-considerations/covid-19-vaccines-us.html).
IIV and RIV can be administered on the same day or any other day before or after other live or inactivated vaccines. Injectable vaccines should be administered in separate anatomic sites when given on the same day.
LAIV may be given on the same day as any other live or inactivated vaccines. However, if two live vaccines are not given on the same day, they should be separated by at least 4 weeks.
We are considering co-locating our COVID-19 drive-through testing site and influenza vaccination sites. Can we vaccinate someone with suspected or confirmed COVID-19 infection?
CDC recommends deferring vaccination for people with suspected or confirmed COVID-19 until they have met criteria for no longer needing quarantine or isolation to avoid exposing healthcare personnel and others. When scheduling or confirming appointments for vaccination, patients should be screened for COVID-19 symptoms and recent exposure.
Which travelers are recommended to get influenza vaccine?
Healthcare providers should vaccinate any person who failed to get vaccinated in the previous vaccination season and who wants to reduce their risk of getting influenza during their upcoming travel, particularly if they are at high risk for influenza-related complications. This includes people who are traveling to the tropics, traveling with organized tourist groups at any time of year, or traveling to the Southern Hemisphere during April–September.
If a patient received a dose of influenza vaccine in June (for example, for international travel), how long should the patient wait before getting vaccinated with the next season's flu vaccine?
There should be a minimum of 4 weeks between the doses in such situations.
What are CDC recommendations for influenza vaccination of people who have already become ill with influenza during the season?
Because more than one type or subtype of influenza virus can circulate in any given influenza season, providers should offer influenza vaccination to unvaccinated people throughout the influenza season, including people who may have had an influenza illness already in the season.
How long does immunity from influenza vaccine last?
Protection from influenza vaccine is thought to persist for at least 6 months. Protection declines over time because of waning antibody levels and because of changes in circulating influenza viruses from year to year. For people who need only 1 dose of influenza vaccine for the season, yearly vaccination (i.e., in July and August) is likely to be associated with suboptimal immunity before the end of the influenza season, particularly among older adults.
Some of my patients refuse influenza vaccination because they insist they "got the flu" after receiving the injectable vaccine in the past. What can I tell them?
There are several reasons why this misconception persists:
    Less than 1% of people who are vaccinated with the injectable vaccine develop flu-like symptoms, such as mild fever and muscle aches, after vaccination. These side effects are not the same as having influenza, but people confuse the symptoms.
    Protective immunity doesn't develop until 1–2 weeks after vaccination. Some people who get vaccinated later in the season (December or later) may be infected with influenza virus shortly afterward. These late vaccinees develop influenza because they were exposed to someone with the virus before they became immune. It is not the result of the vaccination.
    For many people, "the flu" is any illness with fever, cold symptoms or gastrointestinal symptoms. If they get any viral illness, they may blame it on flu vaccine or think they got "the flu" despite being vaccinated. Influenza vaccine only protects against certain influenza viruses, not all viruses.
    Influenza vaccination is our best protection against influenza disease; however, some people who are vaccinated will still get influenza illness despite vaccination.
While vaccine effectiveness (VE) can vary, recent studies show that flu vaccination reduces the risk of flu illness by between 40% and 60% among the overall population during seasons when most circulating flu viruses are well-matched to the flu vaccine. VE is generally lower for adults age 65 years and older. Influenza vaccination has also been shown to reduce influenza disease severity even if someone does get sick after vaccination, and reduces the risk of influenza hospitalization, and deaths in children and adults. Influenza vaccination also reduces the risk of acute cardiac events, like heart attack and heart failure, among people with heart disease.
For more information on this topic, go to: www.cdc.gov/flu/vaccines-work/index.html.
When administering influenza vaccine, is giving patients a vaccine information statement (VIS) mandatory or is it only "recommended"?
Giving patients an influenza Vaccine Information Statement (VIS) is mandatory under the National Childhood Vaccine Injury Act of 1986. The VIS must be given to all adults as well as to parents or guardians of children prior to vaccination. Two VISs are available, one for live attenuated influenza vaccine (LAIV) and one for inactivated influenza vaccine (IIV) and recombinant vaccine (RIV). Each can be found at www.immunize.org/vis/ in multiple languages. The current influenza vaccine VISs are dated August 6, 2021.
The latest VIS for all vaccines plus translations in multiple languages are located on the IAC website www.immunize.org/vis/.
Are there recommendations for the prevention of institutional outbreaks of influenza?
The most important factor in preventing outbreaks is annual vaccination of all residents and staff who work at facilities such as nursing homes, assisted living facilities, and other group living situations. Groups that should be targeted include physicians, nurses, and other personnel in hospitals and outpatient settings who have contact with high-risk patients in all age groups, and providers of home care to high-risk people (for example, visiting nurses, therapists, and volunteers).
We are trying to provide influenza vaccination to all eligible patients during their stay in our hospital. If a patient does not remember if he or she has already received the vaccine this season, should we go ahead and vaccinate?
If a patient or family member cannot remember if the patient received influenza vaccine this season and no record is available, proceed with administering influenza vaccine, even if it might mean an extra dose is given. When a patient reports that they HAVE received influenza vaccine but does not have written documentation, ACIP states that in the specific case of influenza (and pneumococcal polysaccharide) vaccination, patient self-report of being vaccinated can be accepted as evidence of vaccination.
Live Attenuated Influenza Vaccine (LAIV) Issues Back to top
For whom is Flumist Quadrivalent approved?
Flumist Quadrivalent (LAIV4; AstraZeneca) is currently approved by FDA only for healthy non-pregnant people age 2 through 49 years.
Is administering Flumist an aerosol-generating procedure requiring airborne precautions during the COVID-19 pandemic?
No. Giving Flumist is not considered an aerosol-generating procedure. See the CDC web page Interim Guidance for Routine and Influenza Immunization Services During the COVID-19 Pandemic for additional details at: https://www.cdc.gov/vaccines/pandemic-guidance/index.html.
How is Flumist administered?
The vaccine dose (0.2 mL) comes inside a special sprayer device. A plastic clip on the plunger divides the dose into two equal parts. The patient is seated in an upright position with head tilted back. Half of the contents of the sprayer (0.1 mL) is sprayed into each nostril.
Can Flumist be administered to people with minor acute illnesses, such as a mild upper respiratory infection (URI) with or without fever?
Yes, unless clinical judgment suggests nasal congestion is present that might keep the vaccine from making good contact with the nasopharyngeal mucosa. In that case, consider either deferring its use until the congestion resolves or using an appropriate alternative influenza vaccine, if available.
Can a woman who is breastfeeding receive Flumist?
Yes. Breastfeeding is not a contraindication for any routine vaccination including Flumist.
Can Flumist be given to contacts of immunosuppressed patients?
With rare exceptions, yes. Like other live vaccines, Flumist should not be administered to immunosuppressed people. ACIP has stated a preference for using inactivated influenza vaccine for all close contacts of severely immunosuppressed individuals (for example, patients with hematopoietic stem cell transplants) during those periods in which the immunosuppressed person requires care in a protective environment because of the theoretical risk that the live attenuated vaccine virus could be transmitted to the severely immunosuppressed individual and cause disease. Healthcare personnel or other people who have close contact with people with lesser degrees of immunosuppression (for example, people with diabetes, people with asthma taking corticosteroids, or people living with HIV) who are otherwise eligible for Flumist may receive it. No special precautions need to be taken by the vaccinated person.
How long after someone is vaccinated with Flumist must they stay away from a severely immunosuppressed person (a person who is hospitalized in protective [reverse] isolation)?
People should avoid contact with any person who is severely immunosuppressed for at least 7 days after receiving Flumist. There are no restrictions on being in contact with any other patients.
Is Flumist contraindicated for adults with asthma?
Asthma is a precaution for Flumist in people 5 years of age and older.
Can we give Flumist to a person who is taking an influenza antiviral medication?
An antiviral drug active against influenza virus may reduce the effectiveness of Flumist. ACIP has recommended different intervals between the last dose of an antiviral medication and Flumist administration, based upon the half-life of the antiviral medication. The new recommendations are as follows:
  Oseltamivir or zanamivir: wait at least 48 hours after last dose before administering Flumist
Peramivir: wait at least 5 days before administering Flumist
Baloxavir: wait at least 17 days before administering Flumist
If any influenza antiviral medication must be given within 14 days after Flumist administration, the patient should be revaccinated without delay with any age-appropriate inactivated influenza vaccine. All inactivated influenza vaccines and recombinant influenza vaccine (Flublok Quadrivalent) may be administered at any time relative to antiviral medication.
One of our young patients made it impossible to administer the second part of the Flumist dose. What should we do?
A half dose of Flumist (or any other vaccine) is a non-standard dose and should not be counted. If you were unable to give the second half of the vaccine at that same appointment, you will have to provide another full dose of influenza vaccine at another time. If you want to give Flumist again, you should wait four weeks, because it is a live vaccine. Alternatively, you can give inactivated influenza vaccine any time after this partial dose.
For Children Back to top
Which children should receive influenza vaccine?
ACIP recommends annual influenza vaccination for all children age 6 months and older who do not have a contraindication to the vaccine.
Please provide details about the inactivated influenza vaccine options for children younger than 3 years.
Four egg-based quadrivalent inactivated influenza vaccines (IIV4s), all given as intramuscular (IM) injections, are available for children age 6 through 35 months:
  Afluria Quadrivalent (Seqirus): 0.25 mL/dose
Fluarix Quadrivalent (GlaxoSmithKline): 0.5 mL/dose
FluLaval Quadrivalent (GlaxoSmithKline): 0.5 mL/dose
Fluzone Quadrivalent (Sanofi Pasteur): 0.25 mL or 0.5 mL per dose
Flucelvax Quadrivalent (ccIIV4, Seqirus) is available to children ages 24 months (2 years) and older: administer 0.5 mL/dose IM
Which children younger than age 9 years will need 2 doses of influenza vaccine in this influenza season?
Children age 6 months through 8 years should receive a second dose 4 weeks or more after the first dose 1) if they are receiving influenza vaccine for the first time, 2) if they have not received a total of at least two doses of any seasonal influenza vaccine before July 1 of the current year, or 3) if their vaccination history is unknown. The two previous doses need not have been received during the same season or consecutive seasons.
Children who are 8 years old and are recommended to receive two doses during the current season but who have a 9th birthday during the current season before receiving dose 2 should still receive dose 2.
IAC's handout titled "Guide for Determining the Number of Doses of Influenza Vaccine to Give to Children Age 6 Months Through 8 Years" provides additional guidance on this issue; it is available at www.immunize.org/catg.d/p3093.pdf.
When determining whether a child age 2 through 8 years needs one or two doses of influenza vaccine this season, can we count doses of Flumist administered in past years?
Yes. CDC advises that doses of Flumist administered in past seasons can be counted.
If a child age 8 years or younger has had one dose of trivalent and one dose of quadrivalent influenza vaccine in the past, do they need one or two doses for the upcoming season?
They need just one dose of any appropriate influenza vaccine annually.
Can a child age 6–35 months who needs 2 doses of influenza vaccine this season receive a combination of Afluria, Fluzone, FluLaval, Fluarix, or Flumist vaccine?
Yes. The two doses do not have to be the same brand. Afluria Quadrivalent (0.25 mL per dose), Fluzone Quadrivalent (0.25 mL or 0.5 mL per dose), FluLaval Quadrivalent (0.5 mL per dose), and Fluarix Quadrivalent (0.5 mL per dose) are approved by the FDA for use in children age 6–35 months.
Flucelvax Quadrivalent (Seqirus) is an option beginning at age 2 years at 0.5 mL dose. Flumist Quadrivalent is another option for children beginning at age 2 years.
Can a child 36 months through 8 years of age who needs 2 doses of influenza vaccine this season receive a combination of Fluzone, FluLaval, Fluarix, Flucelvax, Afluria, or Flumist vaccine?
Yes. The two doses do not have to be the same brand. Fluzone Quadrivalent (0.5 mL dose), FluLaval Quadrivalent (0.5 mL dose), Fluarix Quadrivalent (0.5 mL dose), Afluria Quadrivalent (0.5 mL dose), Flucelvax (0.5 mL dose) and Flumist Quadrivalent are all options for use in children age 3 years and older.
If a child receives Fluzone Quadrivalent vaccine (0.25 mL) at age 34 or 35 months for the first time and then returns for the second dose at age 37 months, should we give another 0.25 mL dose of Fluzone Quadrivalent or should we give the 0.5 mL dose that is indicated for age 3 years and older?
The child should always receive the dose appropriate for his or her age at the time of the clinic visit; at age 37 months that would be 0.5 mL.
Can a clinic vaccinate children younger than age 3 years with influenza vaccine taken from a multi-dose vial of influenza vaccine? The multi-dose vials contain thimerosal as a preservative.
Yes. Multi-dose vials of inactivated influenza vaccine contain a small amount of thimerosal to prevent bacterial and fungal growth in the vial. Thimerosal-containing vaccines are safe to use in children. No scientific evidence indicates that thimerosal in vaccines causes adverse events unless the patient has a severe allergy to thimerosal. However, a few states have enacted legislation that restricts the use of thimerosal-containing vaccines in children. To find out if your state has such restrictions, check with your state immunization program (see www.immunize.org/coordinators for contact information).
Do any children age 9 years need two total doses during an influenza season?
Yes, but only under one particular set of circumstances. A 9-year-old should receive a dose of influenza vaccine if they turned 9 years old during the current season and already received one dose during the current season when they were 8 years old, AND they did not receive a total of at least two prior doses of influenza vaccine before July 1 of the current year, or their vaccination history before July 1 of the current year is unknown.
There is a debate within my clinical department about not allowing influenza vaccine to be given with DTaP and PCV13. Are there data that state these should not be given concomitantly?
A CDC study has shown a small increased risk for febrile seizures during the 24 hours after a child receives the inactivated influenza vaccine at the same time as the PCV13 vaccine or DTaP vaccine. However, the risk of febrile seizure with any combination of these vaccines is small and ACIP recommends giving these vaccines at the same visit if indicated. See www.cdc.gov/vaccinesafety/concerns/febrile-seizures.html for more information.
For Special Groups Back to top
Is influenza vaccine recommended for pregnant women?
Yes. It is especially important to vaccinate pregnant women because of their increased risk for influenza-related complications and their baby's increased risk of influenza-related illness and hospitalizations during the first 6 months of life.
Influenza vaccination during pregnancy reduces mothers' risk of influenza illness, preterm labor, and their infants' risk of influenza and influenza-related hospitalization in the first 6 months of life.
Most studies of influenza vaccination in pregnant women have administered vaccine in the second or third trimester using inactivated influenza vaccine.
Vaccination can occur in any trimester, including the first. Only inactivated or recombinant influenza vaccines may be given to pregnant women. Flumist, a live vaccine, should not be used in pregnant women.
Why do we vaccinate pregnant women against influenza when it is not recommended to vaccinate infants younger than age 6 months?
ACIP has recommended vaccinating pregnant women with inactivated influenza vaccine since 1997. Pregnant women are at increased risk for complications, hospitalization, and even death from influenza because of the increased physiologic strain of pregnancy on their heart, lungs, and immune system. Vaccination can occur in any trimester, including the first.
Influenza vaccine is not recommended for children younger than age 6 months because it is not approved for this age group. However, vaccinating during pregnancy provides maternal antibodies to the fetus; this helps protect the young infant against influenza during the first 6 months of life. Vaccinating pregnant women protects women, their unborn babies, and their babies after birth.
Does ACIP recommend one influenza product over another for pregnant women?
Pregnant women may receive any inactivated or recombinant influenza vaccine. They should not be given Flumist Quadrivalent because it is a live-virus vaccine.
Can thimerosal-containing vaccine be given to pregnant women?
Yes, unless you live in a state that has enacted legislation restricting use in pregnant women. There is no scientific evidence that thimerosal in vaccines is a cause of adverse events unless the patient has a systemic allergy to thimerosal.
If a patient was vaccinated earlier in the influenza season and later becomes pregnant during the same season, should she be revaccinated due to her pregnancy?
No. The Advisory Committee on Immunization Practices (ACIP) does not recommend more than one dose of influenza vaccine per season, except for certain children being vaccinated for the first time.
I heard that a study suggested an increase in miscarriage among women who received inactivated influenza vaccine. Please provide details.
A CDC-funded study found that women who had been vaccinated early in pregnancy with an influenza vaccine containing the pandemic H1N1 (H1N1pdm09) component and who also had been vaccinated the prior season with an H1N1pdm09-containing influenza vaccine had an increased risk of spontaneous abortion (miscarriage) in the 28 days after vaccination. This study did not quantify the risk of miscarriage and did not prove that influenza vaccine was the cause of the miscarriage. Earlier studies have not found a link between influenza vaccination and miscarriage. A larger follow-up study also funded by CDC which included 3 more years of data found no association between early miscarriage and influenza vaccination regardless of previous influenza season vaccination. These results are reassuring regarding the safety of influenza vaccination of pregnant women.
CDC, ACIP, and the American College of Obstetricians and Gynecologists (ACOG) have not changed the recommendation for influenza vaccination of pregnant women. It is recommended that pregnant women receive influenza vaccine during any trimester of their pregnancy because influenza poses a danger to pregnant women and the vaccine can prevent influenza in pregnant women and their infants.
A co-worker of mine says we are supposed to give infants preservative-free influenza vaccine. Is this true?
No. CDC and ACIP express no preference for preservative-free vaccine for infants or any other group of vaccine recipients.
No scientific evidence exists that thimerosal in vaccines is a cause of adverse events unless the patient has a systemic allergy to thimerosal. However, some states have enacted legislation that restricts the use of thimerosal-containing vaccines. Check with your state immunization manager to see if your state is one of them (www.immunize.org/coordinators).
Do people with diabetes who control their disease with diet need influenza vaccine?
People with a metabolic disease, including diabetes, should receive annual influenza vaccination with an inactivated or recombinant influenza vaccine.
Is influenza vaccine safe to administer to patients with multiple sclerosis?
Yes. Multiple sclerosis is not a contraindication to any vaccine, including influenza and pneumococcal vaccines.
Does influenza vaccine increase the HIV titer in the blood of people with HIV infection?
Although some studies have demonstrated a transient increase in replication of HIV following inactivated influenza vaccine, other studies have not found this. This temporary increase in HIV titer has not been associated with deterioration in either T-lymphocyte counts or clinical condition. ACIP believes that annual influenza vaccination with inactivated vaccine will benefit many HIV-infected people.
Please tell me about Fluad Quadrivalent, one of the influenza vaccines for people age 65 years and older.
In November 2015, FDA licensed Fluad (aIIV3, Seqirus), a trivalent, MF59-adjuvanted inactivated influenza vaccine, for people age 65 years and older. Fluad is now quadrivalent (aIIV4). Fluad was the first adjuvanted influenza vaccine marketed in the U.S. An adjuvant is a substance added to a vaccine to increase its immunogenicity. The MF59 adjuvant is based on squalene, an oil that occurs naturally in many plants and animals. Fluad has been used in Europe since 1997 and is approved in 38 other countries. In contrast to Fluzone High-Dose Quadrivalent (Sanofi Pasteur), Fluad is a standard-dose vaccine, containing 15 mcg of hemagglutinin per virus per dose. In a small observational study among adults age 65 years and older Fluad (trivalent) was associated with greater protection against influenza illness compared to unadjuvanted trivalent standard dose inactivated influenza vaccine. ACIP has not stated a preference for any specific licensed influenza vaccine for people age 65 years and older.
A study published in 2014 found that the injectable vaccine Fluzone High-Dose protected people 65 years and older better than standard-dose Fluzone. Does ACIP preferentially recommend use of Fluzone High-Dose for all people age 65 years and older?
Aging decreases the body's ability to develop a good immune response after getting influenza vaccine, which places older people at greater risk of severe illness from influenza. A higher dose of antigen in the vaccine should give older people a better immune response and therefore provide better protection against influenza. There is published evidence of better protection from Fluzone High-Dose when compared to standard-dose Fluzone (N Engl J Med 2014; 371:635–45); however, ACIP has not stated a preference for any specific licensed influenza vaccine for people age 65 years and older.
Should Fluzone High-Dose Quadrivalent or Fluad Quadrivalent be administered to patients younger than age 65 years?
No. These vaccines are licensed only for people age 65 years and older and are not recommended for younger people.
Would giving an older patient 2 doses of standard-dose influenza vaccine be the same as administering the high-dose product?
No, and this is not recommended.
If a patient is undergoing treatment for cancer, is it safe to vaccinate her or him against influenza?
People with cancer need to be protected from influenza, and they can and should receive inactivated or recombinant influenza vaccine (but not live nasal spray vaccine [Flumist]) even if they are immunosuppressed. Cancer patients and survivors are at higher risk for complications from influenza, including hospitalization and death. Here is a helpful CDC web page on cancer and influenza for patients: www.cdc.gov/cancer/flu.
How soon after bone marrow transplant do we start to vaccinate our patients against influenza?
Inactivated influenza vaccine or recombinant influenza vaccine should be administered beginning at least 6 months after bone marrow transplant and annually thereafter for the life of the patient. A dose of vaccine can be given as early as 4 months after transplant, but a second dose should be considered in this situation. A second dose is recommended routinely for all children younger than 9 years receiving influenza vaccine for the first time.
For Health Care Personnel (HCP) Back to top
Why is influenza vaccination important for HCP?
We already encourage them to stay home from work when they are sick. Unfortunately, by the time a HCP has symptoms of influenza, they may have already exposed many patients since the virus is shed for 1–2 days before symptoms begin. Further, many studies show that HCP often go to work while they are sick and may be infectious to others. Start planning early to make sure all employees in your work setting receive annual influenza vaccination before the influenza season begins.
What are the ACIP recommendations for influenza vaccination of HCP?
Because HCP provide care to patients at high risk for complications of influenza, they should be considered a high-priority group for receiving vaccination. Achieving high rates of vaccination among HCP will protect staff and their patients, and reduce disease burden and healthcare costs. Vaccination rates of HCP are still too low; overall only 81% of HCP report influenza vaccination during the 2019–20 season.
Influenza vaccination key points for HCP include:
All HCP should be educated regarding the benefits of influenza vaccination
Influenza vaccine should be administered annually to all eligible HCP
A signed declination should be obtained from HCP who decline influenza vaccination
Healthcare facilities should monitor HCP influenza vaccination coverage and declination at regular intervals
HCP vaccination coverage should be used as one measure of a patient-safety quality program
In 2011, ACIP published "Immunization of Health-Care Personnel," which includes information about all recommended vaccines (see www.cdc.gov/mmwr/pdf/rr/rr6007.pdf).
Which health care personnel should be vaccinated against influenza?
It is important to vaccinate all healthcare personnel, including paid and unpaid workers who may be exposed to patients or infectious materials. This includes direct patient care staff (e.g., physicians, nurses, and therapists), and staff and volunteers in pharmacy, radiology, laboratory, human resources, facilities management (housekeeping), food services, and laundry. Vaccination should include healthcare staff in all settings, such as hospitals, outpatient clinics, pharmacies, emergency response, nursing homes and assisted living facilities, and home care.
Which employees of congregate living facilities, such as assisted living facilities and nursing homes, should be vaccinated against influenza?
All people working in long-term care facilities who do not have a valid contraindication should receive annual influenza vaccination.
What is the Joint Commission's recommendation on vaccinating healthcare workers against influenza?
Since January 2007 the Joint Commission has required accredited organizations to offer annual influenza vaccination to staff, volunteers, and licensed independent practitioners who have close patient contact.
I would like to help establish a policy of mandatory influenza vaccination for HCP in our facility and would like to learn from others. Can you help?
Every year more healthcare facilities are adopting mandatory vaccination policies for their employees. IAC has included more than 1,150 of these on its Honor Roll for Patient Safety, which gives special recognition to institutions that enforce mandatory vaccination for all personnel who are in the vicinity of a patient (including volunteers and housekeeping staff). To read about the policies of the various facilities included in the Honor Roll, go to www.immunize.org/honor-roll/influenza-mandates/honorees.asp. In addition, the National Adult and Influenza Immunization Summit has developed tools to assist post-acute and long-term care facilities that plan to implement influenza vaccination requirements for HCP at www.izsummitpartners.org/naiis-workgroups/influenza-workgroup/tools-for-ltcf/. We hope reviewing these policies and tools will give you the information you need to assist in developing a policy for your facility.
We have a mandatory vaccination policy in our facility; however, we allow employees to choose not to be vaccinated after filling out and signing an informed declination form. What can we do to achieve assurances that patient safety is still maintained?
Though vaccination is the most effective means of protecting your patients from influenza, there may be instances where employees are not vaccinated for medical or personal reasons. In these instances, you may want to consider reassigning unvaccinated workers to non-patient areas or requiring that they wear masks throughout the influenza season.
Does the federal law that requires providing patients with VISs apply when administering influenza vaccine to employees and volunteers in hospitals or other workplaces?
If a vaccine is covered under the National Childhood Vaccine Injury Act—and almost all vaccines routinely administered to adults are (with the exception of PPSV and zoster)—it is mandatory under federal law to give the VIS for that vaccine to the vaccinee. Therefore, when you give influenza vaccine to employees and staff, you are required by law to provide them with a VIS.
Why does CDC recommend that we consider obtaining a signed declination from HCP who refuse influenza vaccination?
Some studies have shown an increase in HCP influenza vaccine acceptance when decliners are required to sign such a statement. In addition, such statements can help a vaccination program assess the reasons for declination and plan future educational efforts. IAC has posted the following suggested declination form for healthcare workers at www.immunize.org/catg.d/p4068.pdf.
Please tell me which professional associations have endorsed mandatory influenza vaccination for HCP and have created policy statements.
There are many professional associations that have issued policy statements supporting mandatory healthcare worker influenza vaccination. You can find information about these organizations as well as a list of more than 1,150 healthcare settings that have implemented mandatory vaccination programs on IAC's website at IAC's Influenza Vaccination Honor Roll web section at www.immunize.org/honor-roll/influenza-mandates/.
Contraindications and Precautions Back to top
What are the contraindications and precautions for people with a history of a severe allergic reaction to a previous influenza vaccination?
A severe allergic reaction to any influenza vaccine is a contraindication to receiving additional doses of the same vaccine or receiving any egg-based influenza vaccines. The following table summarizes the contraindications and precautions for different types of influenza vaccine and is adapted from table 3 on page 5 of the 2021–22 influenza ACIP recommendations at www.cdc.gov/mmwr/volumes/70/rr/pdfs/rr7005a1-H.pdf:
Vaccine (of any valency) associated with previous serious or anaphylactic reaction Available 2021–22 influenza vaccines
  Egg-based IIV4s
and LAIV4
ccIIV4 RIV4
Any egg-based IIV or LAIV Contraindication Precaution Precaution
Any ccIIV Contraindication Contraindication Precaution
Any RIV Contraindication Precaution Contraindication
Unknown influenza vaccine Allergist consultation recommended
Note regarding patients having either of the above precautions for either ccIIV or IIV: Use of ccIIV4 and RIV4 in such instances should occur in an inpatient or outpatient medical setting under the supervision of a healthcare provider (HCP) who can recognize and manage severe allergic reaction; HCPs can also consider consulting with an allergist to help identify the vaccine component responsible for the reaction.
What are the contraindications and precautions for Flumist Quadrivalent?
Contraindications are:
a history of severe allergic reaction to a vaccine component (except egg—see next question) or after a previous dose of any influenza vaccine
concomitant aspirin or salicylate-containing therapy in children and adolescents because of the risk of Reye syndrome
children age 2 through 4 years who have received a diagnosis of asthma or whose parents or caregivers report that a healthcare provider has told them during the preceding 12 months that their child had wheezing or asthma or whose medical record indicates a wheezing episode during the preceding 12 months
immunosuppression due to any cause including medications or HIV infection
cerebral spinal fluid (CSF) leak, cochlear implant, or anatomic asplenia or functional asplenia (e.g., due to sickle cell anemia)
close contacts and caregivers of severely immunosuppressed people who require a protected environment (e.g., reverse isolation in a hospital)
pregnancy
receipt of influenza antiviral medication within the previous 48 hours for oseltamivir and zanamivir, previous 5 days for peramivir, and previous 17 days for baloxavir
Precautions are:
moderate or severe acute illness with or without fever
history of Guillain-Barré syndrome within 6 weeks after a dose of influenza vaccine
asthma in a person age 5 years or older
underlying medical conditions that might predispose to complications after influenza virus infection, such as chronic pulmonary, cardiovascular (except isolated hypertension), renal, hepatic, neurologic, hematologic, or metabolic disorders including diabetes mellitus
What is the latest ACIP guidance on influenza vaccination and egg allergy?
ACIP recommends that people with a history of egg allergy who have experienced only hives after exposure to egg should receive influenza vaccine without specific precautions (except the standard 15-minute observation period for syncope). Any age-appropriate vaccine may be used. For people who report having had an anaphylactic reaction to egg (more severe than hives), if a vaccine other than Flucelvax Quadrivalent (ccIIV, Seqirus) or Flublok Quadrivalent (RIV4, Sanofi Pasteur) is given, the vaccine should be administered in an inpatient or outpatient medical setting supervised by a healthcare provider who is able to recognize and manage severe allergic conditions. Although not specifically recommended by ACIP, providers may prefer administering an age-appropriate egg-free vaccine (ccIIV4 or RIV4) for patients with severe egg allergy.
A previous severe allergic reaction to influenza vaccine, regardless of the component suspected to be responsible for the reaction, is a contraindication to future receipt of the vaccine. For a complete list of vaccine components (i.e., excipients and culture media) used in the production of the vaccine, check the package insert (available at www.immunize.org/fda) or go to www.cdc.gov/vaccines/pubs/pinkbook/downloads/appendices/B/excipient-table-2.pdf.
For more details about giving influenza vaccine to people with a history of egg allergy, see the ACIP guidance at www.cdc.gov/mmwr/volumes/69/rr/pdfs/rr6908a1-H.pdf. You also may find the IAC handout "Influenza Vaccination of People with a History of Egg Allergy" helpful (see www.immunize.org/catg.d/p3094.pdf).
Is allergy to chicken or duck feathers a contraindication to receipt of an egg-based influenza vaccine?
No.
The influenza VIS states that giving pneumococcal conjugate vaccine and inactivated influenza vaccine simultaneously to young children may increase the risk of febrile seizures. Can we continue to give these two vaccines at the same time?
Yes, you can. Some, but not all, studies have reported increased rates of febrile seizures among children, especially those age 12 through 23 months, who received simultaneous vaccination with IIV and pneumococcal conjugate vaccine (PCV13, Pfizer) or DTaP vaccine (Daptacel, Infanrix, Pediarix, Pentacel), when compared with children who received these vaccines separately. However, because of the risks associated with delaying either of these vaccines, ACIP does not recommend administering them at separate visits or deviating from the recommended vaccine schedule in any way.
Febrile seizures, occurring in 2% to 5%, of all children, are not uncommon, and they are generally benign. Healthcare providers should be prepared to answer parents' questions about febrile seizures and fever when discussing vaccinations. Here is a helpful CDC resource: www.cdc.gov/vaccinesafety/Concerns/FebrileSeizures.html.
We usually instruct our patients that they should separate vaccinations and allergy shots by at least 24 hours because if there were a reaction to one or the other, it wouldn't be possible to determine which was the cause. This becomes problematic during influenza vaccination season. What should we do?
The probability of a serious allergic reaction following any vaccine is extremely low if the person is properly screened. ACIP has not issued a recommendation that desensitization injections and vaccines be separated by any specific time period; consequently, we feel that you should take the opportunity to vaccinate.
When I was 5 years old, I had Guillain-Barré syndrome (GBS) unrelated to vaccination. I am now 35 with no residual effects of the GBS. I am a nurse and my facility requires employees to receive influenza vaccine. Is it safe for me to be vaccinated?
Yes. A history of GBS unrelated to influenza vaccine is not a contraindication or precaution to influenza vaccination. GBS within 6 weeks following a previous dose of influenza vaccine is considered a precaution for use of influenza vaccines.
Administering Vaccines Back to top
What is the most up-to-date Influenza Vaccine Information Statement (VIS) for the 2021–22 influenza season?
Both the inactivated and recombinant influenza vaccine VIS and the live influenza vaccine VIS were updated on August 6, 2021. These VISs and translations in multiple languages are available here: www.immunize.org/vis/.
Which formulations of influenza vaccines are licensed for various age groups?
Influenza vaccines differ with regard to age group indications. IAC has a handout that summarizes each of the products available for the current influenza vaccination season at www.immunize.org/catg.d/p4072.pdf. ACIP does not state a preference for one influenza vaccine over another for people for whom more than one vaccine is recommended and is age- and health condition-appropriate.
Where can I find resources to help me plan mass vaccination clinics for influenza or COVID-19 vaccines?
Multiple resources are available on the CDC website at: www.cdc.gov/vaccines/hcp/admin/mass-clinic-activities/index.html and at IAC's "Mass Vaccination Resources" website at: www.mass-vaccination-resources.org.
We are considering co-locating our COVID-19 drive-through testing site and influenza vaccination sites. Can we vaccinate someone with suspected or confirmed COVID-19 infection?
CDC recommends deferring vaccination for people with suspected or confirmed COVID-19 until they have met criteria for no longer needing quarantine or isolation to avoid exposing healthcare personnel and other patients. When scheduling or confirming appointments for vaccination, patients should be screened for COVID-19 symptoms and recent exposure.
Is it acceptable to draw up vaccine into syringes at the beginning of the day? If it isn't, how much in advance can this be done?
CDC discourages the practice of prefilling vaccine into syringes for several reasons, including:
the increased possibility of administration and dosing errors
  the increased risk of inappropriate storage temperature
  the probability of bacterial contamination
the probability of reducing the vaccine's potency over time
Prefilling vaccine into syringes also violates basic medication administration guidelines, which state that an individual should administer only those medications he or she has prepared and drawn up.
Although pre-drawing vaccine is discouraged, a limited amount of vaccine may be pre-drawn in a mass-immunization clinic setting under the following conditions:
Only a single type of vaccine (for example, influenza) is administered at the mass-immunization clinic setting
  Vaccine is not drawn up in advance of its arrival at the mass-vaccination clinic site
  These pre-drawn syringes are stored at temperatures appropriate for the vaccine they hold
No more than 1 vial or 10 doses (whichever is greater) is drawn into syringes
  Clinic staff monitor patient flow carefully and avoid drawing up unnecessary doses or delaying administration of pre-drawn doses
At the end of the clinic day, all remaining vaccine in syringes prefilled by staff should be discarded.
Can people who are currently infected with COVID-19 be vaccinated against influenza?
In general, people who are in quarantine following exposure to someone with COVID-19 or in isolation due to infection with COVID-19 should not be brought to a vaccination location to avoid exposing others to COVID-19. For people with moderate or severe COVID-19, vaccination should generally be deferred until they have recovered. For patients with mild or asymptomatic infection with SARS-CoV-2, influenza vaccination may also be deferred to avoid confusing COVID-19 symptoms with potential influenza vaccination-related reactions. Aside from these considerations, there are no other reasons to further defer influenza vaccination following infection with COVID-19. Periodically check CDC guidance on influenza vaccination during the COVID-19 pandemic for updates at www.cdc.gov/vaccines/pandemic-guidance/index.html.
Does ACIP prefer that healthcare professionals administer high-dose or adjuvanted influenza vaccine to people age 65 years and older, or is standard-dose influenza vaccine acceptable?
ACIP has expressed no preference.
The pneumococcal conjugate vaccine (PCV13) package insert says that in adults, antibody responses to PCV13 were diminished when given with inactivated influenza vaccine. Does this mean we should not give PCV13 and influenza vaccine at the same visit?
The available data have been interpreted that any changes in antibody response to either of the vaccines' components were clinically insignificant. The antibody response was only lowered for three components, and ONLY in patients younger than 65 years of age. In this age group, if PCV13 is recommended, it means there is a high-risk of invasive pneumococcal disease for those unvaccinated. If PCV13 and influenza vaccine are both indicated and recommended, they should be administered at the same visit. See the PCV13 ACIP recommendations at www.cdc.gov/mmwr/pdf/wk/mm6337.pdf, page 824.
We have had three employees who have tested positive for influenza by nasal swab within 2 weeks of receiving Fluarix Quadrivalent (GlaxoSmithKline) vaccine. Is there a time period after receiving influenza vaccine that a nasal swab can give a false positive result?
Inactivated influenza vaccines, including Fluarix, are not known to cause false positive nasal swab tests. However, false positive test results are possible with rapid tests, and these are more likely to occur when influenza prevalence in the area is low. For more information regarding interpretation of rapid influenza tests see www.cdc.gov/flu/professionals/diagnosis/rapidlab.htm.
What is the preferred anatomic site for administration of inactivated influenza vaccine (IIV) and recombinant influenza vaccine?
IIV should be administered in the anterolateral thigh muscle of an infant or young child. IIV and RIV (approved for people age 18 years and older) should be administered in the deltoid muscle of an older child, adolescent, or adult. The anterolateral thigh muscle can also be used for an older child, adolescent, or adult if necessary. It is critical that intramuscular influenza vaccine be injected into a muscle. Influenza vaccination season is an opportune time to review proper intramuscular injection techniques with your staff. IAC has prepared a handout on how to administer intramuscular vaccine injections (available at www.immunize.org/catg.d/p2020.pdf) that can be used as a staff training tool.
Some of our patients believe that they have had reactions to influenza vaccine in the past and request the dose to be split into 2 doses administered on different days. Is this an acceptable practice?
This is definitely not an acceptable practice. Doses of influenza vaccine (or any other vaccine) should never be split into "half doses." If a "half dose" is administered, it should not be accepted as a valid dose and should be repeated as soon as possible with a full age-appropriate dose.
Should staff at drive-through influenza vaccination clinics encourage drivers to park and wait for 15 minutes after vaccination to make sure they don't have a syncopal (fainting) episode?
Yes. Syncope may occur following any vaccination. It is prudent for all people to be observed for syncope for at least 15 minutes after any vaccination.
Sometimes I am unable to get 10 doses of influenza vaccine out of a 5.0 mL (10-dose) vial. Do you have any suggestions?
Certain vaccine syringes have small hubs where a volume of the vaccine that is withdrawn from the vial collects and is not available to be injected. Syringes without a hub are available; their use results in less vaccine wastage.
When removing both pediatric (0.25 mL) and adult (0.5 mL) doses from a multi-dose vial of Fluzone Quadrivalent, we can get more than 10 doses from the 5.0 mL vial. Can we continue to remove doses from the vial until it is empty?
No. Only the number of doses indicated in the manufacturer's package insert should be withdrawn from the vial. For a 5.0 mL vial of Fluzone Quadrivalent this is 10 doses. For Afluria Quadrivalent 5.0 mL multi-dose vial, the package insert states that the stopper can be punctured up to 20 times, allowing up to 20 doses of 0.25 mL dose for children age 6–35 months old. After the maximum number of doses has been withdrawn or number of punctures of the stopper has met the FDA-recommended limit, the vial should be discarded, even if there is vaccine remaining in the vial and the expiration date has not been reached.
We inadvertently administered a 0.5 mL dose of Flucelvax (Seqirus) to a 1-year-old child before realizing that the vaccine is only licensed for use in people age 2 years and older. Do we need to repeat the dose with an age-appropriate product?
No, the dose does not need to be repeated. However, this is a vaccine administration error as this formulation is not licensed for children younger than age 2 years. Clinicians should carefully select an influenza vaccine that is licensed for the age group of the person being vaccinated. Currently Fluzone Quadrivalent 0.25 mL or 0.5 mL (Sanofi Pasteur), FluLaval Quadrivalent 0.5 mL (GSK), Fluarix Quadrivalent 0.5 mL (GSK), and Afluria Quadrivalent 0.25 mL (Seqirus) are the only inactivated influenza vaccines approved for use in children age 6 months through 23 months. Flumist Quadrivalent (AstraZeneca) is approved for healthy non-pregnant people age 2 through 49 years.
If the child needs a second dose of influenza vaccine, an age-appropriate vaccine should be selected. IAC's educational piece "Influenza Vaccine Products for the 2021–22 Influenza Season" (available at www.immunize.org/catg.d/p4072.pdf) provides helpful information on the wide variety of influenza  vaccines in use this season.
If the recombinant influenza vaccine (RIV4, Flublok Quadrivalent) was given inadvertently to a person younger than 18 years, can it be counted? Would there be any adverse side effects from this error?
Flublok Quadrivalent is not licensed for people younger than 18 years of age, so there are no data regarding safety and efficacy in this age group. However, no serious side effects would be expected. The dose does not need to be repeated. Even if no adverse reaction occurs, we request that vaccine administration errors like this be reported to the Vaccine Adverse Events Reporting System at www.vaers.hhs.gov.
A 3 year old patient received 0.25mL of Fluzone. Does this patient need to return for a repeat dose and when?
If the error is discovered on the same clinic day you can administer the other "half" of the Fluzone Quadrivalent dose. If the error is discovered the next day or later, the dose should not be counted. The child should be recalled to the office as soon as possible and given a full age-appropriate repeat dose of influenza vaccine.
A 1-year-old was inadvertently given a 0.25 mL dose of FluLaval (or Fluarix) rather than the recommended 0.5 mL dose. What should we do?
If the error is discovered on the same clinic day you can administer the other "half" of the FluLaval Quadrivalent (or Fluarix Quadrivalent) dose. If the error is discovered the next day or later, the dose should not be counted. The child should be recalled to the office as soon as possible and given a full age-appropriate repeat dose, either a 0.5 mL dose of FluLaval Quadrivalent, a 0.5 mL dose of Fluarix Quadrivalent, a 0.25 or 0.5 mL dose of Fluzone Quadrivalent, or a 0.25 mL dose of Afluria Quadrivalent.
Storage and Handling  
How should influenza vaccines be stored?
All influenza vaccines (inactivated, recombinant, and live attenuated vaccines) should be stored at refrigerator temperature of 2° through 8°C (36° through 46°F). No influenza vaccine should be frozen. Influenza vaccine exposed to freezing temperature should not be used.
Back to top
This page was updated on September 16, 2021.
This page was reviewed on September 16, 2021.
 
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Immunization Action Coalition  •  2550 University Avenue West  •  Suite 415 North  •  Saint Paul, Minnesota  •  55114
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This website is supported in part by a cooperative agreement from the National Center for Immunization and Respiratory Diseases (Grant No. 1NH23IP922654) at the Centers for Disease Control and Prevention (CDC) in Atlanta, GA. The website content is the sole responsibility of IAC and does not necessarily represent the official views of CDC.