Ask the Experts is one of our most popular destinations for healthcare professionals. Our experts provide clear, easy-to-understand answers to commonly asked questions about vaccines and their use.
Because she has functional asplenia, she is due for the second dose of the primary series (assuming 8 weeks have passed since the first primary series dose). Because she has a high-risk medical condition she will need periodic booster doses. If she is younger than age 7 years when she receives the second dose of her primary series, she should receive her first booster dose 3 years after completing the primary series. She should then receive a booster dose every five years thereafter. If she is age 7 years or older when she receives the second primary dose she should receive her first booster dose 5 years after the completing the primary series and every five years thereafter.
Yes. HPV vaccine should be administered to people who are already sexually active if age appropriate. Routine catch-up vaccination of any person not vaccinated on schedule as a preteen is recommended through age 26 years, and vaccination may be considered with shared clinical decision-making between ages 27 and 45. Ideally, patients should be vaccinated before the onset of sexual activity; however, people who have already been infected with one or more HPV types will still be protected from other HPV types in the vaccine that have not been acquired.
Prevaccination serologic testing for HAV (measuring either total anti-HAV or IgG anti-HAV) is not indicated for children because of the low prevalence of infection in children. It also is not routinely recommended for adults but may be considered in some settings to reduce costs associated with vaccinating people who are already immune. Prevaccination testing should not be used if it poses a barrier to vaccinating susceptible people, especially people who are difficult to access.
Prevaccination testing is most likely to be cost-effective for adults who were either born in or lived for long periods of time in areas of the world with high or intermediate hepatitis A endemicity. When evaluating people from populations with high rates of previous HAV infection, vaccination history also should be obtained, if feasible. If testing or vaccination history is not available, do not postpone vaccinating. There is no harm in vaccinating a person who has had natural infection or previous doses of vaccine.
Children and adolescents who have been diagnosed with acute dengue should wait at least 6 months after the date the dengue illness is confirmed to begin the vaccine series.
First of all, make sure all your patients are fully vaccinated.
In certain circumstances, MMR is recommended for infants age 6 through 11 months. Follow the guidance of your state or local health department concerning vaccinating infants in this age group in your specific outbreak situation. Do not count any dose of MMR vaccine as part of the 2-dose series if it is administered more than 4 days before a child’s first birthday. Instead, repeat the dose when the child is age 12 months, and at least 4 weeks after the early dose.
In the case of a local outbreak, you also might consider vaccinating children age 12 months and older at the minimum age (12 months, instead of 12 through 15 months) and giving the second dose 4 weeks later (at the minimum interval) instead of waiting until age 4 through 6 years.
Finally, remember that infants too young for routine vaccination and people with medical conditions that contraindicate measles immunization depend on high MMR vaccination coverage among those around them. Be sure to encourage all your patients and their family members to get vaccinated if they are not immune.
In addition to these steps, you should be prepared in advance for a suspect measles case to present to your practice. CDC has materials to help healthcare facilities prepare for the possibility of a measles case at www.cdc.gov/measles/php/toolkit/index.html (see Checklist for Healthcare Workers).
Vaccine may be used through the last day of the month indicated on the expiration date. After that, do not use it. Monitor your vaccine supply carefully so that vaccines do not expire.
In August 2024, FDA changed the dosing interval for a 2-dose series of Bexsero (MenB-4C, GSK) from 1 month to 6 months, and recommends that people who receive a second dose of Bexsero less than 6 months after dose 1 receive a third dose at least 6 months after dose 1 and at least 4 months after dose 2. However, no additional primary series doses are recommended for people who previously completed the 2-dose series with the shorter interval, in accordance with the licensed and recommended Bexsero schedule at the time.
In June 2019, ACIP voted to recommend MenB booster doses for people at ongoing increased risk of meningococcal serogroup B disease and the recommendation was published in 2020 (www.cdc.gov/mmwr/volumes/69/rr/pdfs/rr6909a1-H.pdf). As long as you use Bexsero (MenB-4C) as the booster dose, this patient should be given a booster dose of Bexsero now and receive subsequent booster doses every 2–3 years.
The two types of MenB vaccine work differently and are not interchangeable. The only time ACIP recommends restarting the primary series is if the brand used for the primary series is not known or is unavailable.
Both brands of DTaP-IPV pediatric combination vaccines (Kinrix, GSK; Quadracel, Sanofi) are only licensed for use as the fifth dose of the DTaP vaccine series and the fourth (or fifth, for Quadracel) dose of the IPV series in children age 4 through 6 years. CDC has provided this guidance for when Kinrix or Quadracel are given off-label:
However, you should check with your state immunization program to see what they will accept. Checking with your state is particularly important for validating a last dose of IPV vaccine administered before the fourth birthday. Their guidance may vary depending on the date of administration or your upcoming travel plans. Contact information can be found here: www.immunize.org/coordinators.
No. Children with Down syndrome should receive all indicated vaccines on the recommended schedule. These children are often at greater risk for complications from vaccine-preventable diseases than are children without Down syndrome.
Both vaccines have been demonstrated to be safe, with side effects typical of those in older age groups. The most common local reaction in this age group is pain at the injection site; the most common systemic symptom in older children was fatigue and in younger children (6 through 23 months) irritability/crying and sleepiness were most common. Fever may occur after either vaccination. Febrile seizures can occur in infants and young children ages 6 months through 5 years as a result of any condition that causes a fever (most common with high fevers). Febrile seizures are uncommon after vaccination. Febrile seizures were rare after mRNA COVID-19 vaccine clinical trials in this age group, and CDC continues to monitor for this adverse event following vaccination in infants and young children.
No cases of myocarditis were reported during the clinical trials for either vaccine. To date, post-authorization surveillance has not detected an increased risk for myocarditis and pericarditis following mRNA COVID-19 vaccination in children ages 6 months–4 years (Pfizer-BioNTech) and ages 6 months–5 years (Moderna).
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 recipient 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.
Immunize.org offers a 1-page clinic resource demonstrating how to administer intramuscular or intranasal influenza vaccines: www.immunize.org/wp-content/uploads/catg.d/p2024.pdf.
The first step is to inform the parent/patient that you administered the wrong vaccine. Next, follow these guidelines:
Note that DTaP is neither approved nor recommended for people older than 6 years (except hematopoietic stem cell transplant recipients in some situations; see www.cdc.gov/vaccines/hcp/imz-best-practices/altered-immunocompetence.html).
Shingrix has been studied in people with certain types of immunocompromise and has been shown to have moderate to high effectiveness against herpes zoster and postherpetic neuralgia. Because the causes of immunocompromise are so varied, the effectiveness and durability of protection provided by Shingrix also may vary depending upon the precise nature and severity of immunocompromise in a given individual.
For children, the first dose should be given at age 12 months with a second dose given at age 4 through 6 years. The second dose could be given earlier, if necessary, as long as there is a 3-month (12-week) interval between doses. Although a 3-month minimum interval is recommended in children younger than age 13, the second dose does not need to be repeated if separated from the first dose by a shorter interval of at least 4 weeks.
All children age 13 years and older as well as adults without evidence of immunity should also have documentation of 2 doses of varicella vaccine, separated by a minimum interval of 4 weeks.
Administer the PCV20. CDC recommendations were updated in October 2024 to state that recipients of PCV13 should receive PCV20 or PCV21 at least one year after the dose of PCV13. CDC no longer recommends PPSV23 as an option following PCV13. PPSV23 is only recommended for adults who receive a dose of PCV15 and have never had a dose of PPSV23 before.
No future doses of any pneumococcal vaccine are currently recommended following a dose of PCV20 or PCV21.
This situation is not addressed in the ACIP guidelines for meningococcal conjugate vaccine. It is the CDC meningococcal subject matter expert’s opinion that this patient should receive 2 doses of MenACWY separated by at least 8 weeks, followed by a booster dose of MenACWY every 5 years thereafter. The concern is that having had only MPSV4 (Menomune, Sanofi, unavailable since 2017) previously, she may not have an adequate booster response to a single dose of MenACWY.
In clinical trials, HPV vaccines were shown to be highly effective (more than 95%) for prevention of HPV vaccine-type infection and disease among people without prior infection with the HPV types included in the vaccine. The most likely explanation for this situation is that the patient was exposed to at least HPV types 16 and 18 prior to vaccination. The HPV vaccine is not effective in preventing infection from HPV types a person has been exposed to prior to vaccination. The vaccine also cannot prevent progression of HPV infection or HPV-related disease. The 9vHPV vaccine protects against 9 different types of HPV.
Dengvaxia is contraindicated for people with a history of immediate hypersensitivity to any vaccine component or a previous dose of this vaccine. A complete list of vaccine components is available in the package insert at www.fda.gov/media/124379/download.
Dengvaxia is a live-attenuated vaccine and also is contraindicated in children with severe immunodeficiency or immunosuppression due to underlying disease or therapy, including children with symptomatic HIV infection or CD4+ T-lymphocyte count of less than 200 per cubic milliliter.
Lack of laboratory evidence of previous dengue infection is also a contraindication to Dengvaxia. www.cdc.gov/vaccines/vpd/dengue/hcp/recommendations.html.
In recent years, mumps outbreaks have occurred primarily in populations in institutional settings with close contact (such as residential colleges) or in close-knit social groups. The current routine recommendation for 2 doses of MMR vaccine appears to be sufficient for mumps control in the general population, but insufficient for preventing mumps outbreaks in prolonged, close-contact settings, even where coverage with 2 doses of MMR vaccine is high.
In January 2018, the Advisory Committee on Immunization Practices (ACIP) published guidance for MMR vaccination of people at increased risk for acquiring mumps during an outbreak. People previously vaccinated with 2 doses of a mumps virus–containing vaccine who are identified by public health authorities as being part of a group at increased risk for acquiring mumps because of an outbreak should receive a third dose of a mumps virus–containing vaccine to improve protection against mumps disease and related complications. Either brand of MMR vaccine may be used. More information about this recommendation is available at www.cdc.gov/mmwr/volumes/67/wr/pdfs/mm6701a7-H.pdf.
Serologic testing for immunity to hepatitis A virus (HAV) is not necessary after routine HepA vaccination of infants, children or adults. Testing for the presence of anti-HAV antibody one month or more after completing the HepA vaccination series is recommended only for people whose future clinical management depends on knowing their immune status and for whom revaccination might be indicated, such as people living with HIV and other immunocompromised persons (such as transplant recipients and people vaccinated while receiving chemotherapy). In such individuals, if the results of postvaccination testing do not show an adequate immune response (10 mIU/mL or higher), revaccination with a complete series is recommended, followed by a second postvaccination serologic test. If that second test remains negative, no additional vaccination is recommended; however, the patient should be counseled on strategies to avoid exposure to HAV and the need for IG if an exposure occurs. If vaccination results in seroconversion, insufficient data are available to make recommendations concerning repeat testing, booster doses or revaccination.
The expiration date is the date by which the vaccine should be used. Vaccines may be used up to and including this date unless otherwise stated in the manufacturer’s product information. The expiration date is based on the assumption that the vaccine has been properly handled and that it has not become contaminated.
Some vaccines expire within a certain time after opening or after reconstitution. Multidose vials that contain bacteriostatic agents that prevent the growth of bacteria and may be used until the expiration date printed on the vial unless they become contaminated. Single-dose vials and manufacturer-filled syringes do not contain bacteriostatic agents. Once the cap has been removed or the sterile seal has been broken on these vaccines, they should be administered. Lyophilized (freeze-dried) vaccine must be used within a specified time frame after it has been reconstituted. You may find an educational piece from Immunize.org titled “Vaccines with Diluents: How to Use Them” helpful. It’s available at www.immunize.org/wp-content/uploads/catg.d/p3040.pdf.
During an outbreak of meningococcal B disease, swift protection of those at risk is prioritized and CDC subject matter experts do not recommend delaying vaccination in order to locate records. Student health services with documentation of MenB vaccination (including brand) of incoming students, either in a state immunization registry or in student health records, will be able to respond most efficiently to an outbreak.
Students whose primary series of MenB vaccine was completed at least 1 year before the outbreak (or as little as 6 months before the outbreak, if recommended by public health) should receive a single booster dose of the same brand of MenB vaccine. If the same brand is unavailable, they should restart the primary series with the available brand. If the brand of the primary series is unknown, administer a dose of the available product and counsel the recipient to request records of the primary series: if the primary series brand is different, then in order to ensure optimal protection, the recipient should be given a booster dose of the primary series product a minimum of 4 weeks after the most recent MenB dose, or they should complete a new 3-dose primary series with the available product for accelerated protection.
This issue is discussed in the special populations section of CDC’s “General Best Practices for Immunization” (www.cdc.gov/vaccines/hcp/imz-best-practices/special-situations.html#cdc_report_pub_study_section_8-vaccinating-persons-with-increased-bleeding-risk). Intramuscular (IM) injections should be scheduled shortly after antihemophilia therapy or prior to a dose of anticoagulant, if the patient receives this treatment. For both IM and subcutaneous (subcut) injections, a fine needle (23 gauge or smaller) should be used and firm pressure applied to the site, without rubbing, for at least 2 minutes. Provide information to the recipient or caregiver about the risk for hematoma from the injection. Providers should not administer a vaccine by a route that is not approved by the FDA for that particular vaccine (e.g., administration of IM vaccines by the subcut route).
Comirnaty (Pfizer-BioNTech) mRNA COVID-19 vaccine is FDA-licensed for use in ages 5 years through 64 years with at least one underlying condition that puts them at risk for severe COVID-19 infection and individuals 65 years and older
mNexspike (Moderna) is FDA-licensed for use in ages 12 through 64 years with at least one underlying condition that puts them at risk for severe COVID-19 infection and individuals 65 years and older
Nuvaxovid (Sanofi-Novavax) is FDA-licensed for use in ages 12 through 64 years with at least one underlying condition that puts them at risk for severe COVID-19 infection and individuals 65 years and older
Spikevax (Moderna) mRNA COVID-19 vaccine is FDA-licensed for use in ages 6 months through 64 years with at least one underlying condition that puts them at risk for severe COVID-19 infection and individuals 65 years and older
Although the FDA licenses are limited in the age group younger than 65 years to those with underlying conditions that put them at risk for severe COVID-19 infection, the ACIP has recommended use based on individual decision-making (i.e., shared clinical decision-making) for all people age 6 months and older. This means that it is acceptable standard of care to offer COVID-19 vaccination to people in this age group without a high-risk condition when vaccination is desired.
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.
Vaccination involves active immunization, where an antigen is administered to a recipient to activate the recipient’s immune system and generate an immune response (which includes developing antibodies). Active immunization may require up to 2 weeks to have its full protective effect, and sometimes a series of vaccinations is required. Protection may last for months or be life-long, depending upon the type of immune response triggered. The effectiveness of a vaccine depends on the recipient’s immune system.
Nirsevimab (Beyfortus, Sanofi) and clesrovimab (Enflonsia, Merck) are injectable, long-acting monoclonal antibody products that gives the recipient direct, immediate protection through passive immunization. The antibodies circulate in the bloodstream and recognize and attach to the RSV virus if encountered, leading to elimination of the virus. These antibodies protect the patient for at least 5 months until they gradually break down and disappear. The highest risk of severe RSV infection and hospitalization for children is during their first RSV season as an infant. RSV preventive antibody products will not prevent children from getting RSV infections in future seasons, but the general risk of hospitalization due to RSV in childhood is far lower after infancy.
Yes. You should draw the blood first and then administer the first dose of vaccine, as transient HBsAg-positivity has been detected after a dose of HepB (see related question).
Yes. The DTaP in the Pentacel can be counted. Although Pentacel is licensed as a 4-dose series and this may represent a fifth dose of Pentacel (in which case it would be off-label use), the dose of DTaP counts as the fifth dose of DTaP.
The same principle applies to Vaxelis (DTaP-IPV-Hib-HepB, MCM), which is licensed for use in children ages 6 weeks through 4 years as a 3-dose series of vaccinations routinely recommended at age 2 months, 4 months, and 6 months. The DTaP in a dose of Vaxelis inadvertently administered after the 5th birthday or as the 4th or 5th dose of DTaP (off-label use) may be counted as valid and does not need to be repeated.
ACIP and the FDA have determined that Shingrix is acceptably safe in immunocompromised individuals. Immune-mediated diseases were evaluated in six studies in five immunocompromised groups and were not increased among recombinant zoster vaccine (RZV, Shingrix) recipients. One study in patients with hematologic cancers reported on graft-versus-host-disease among hematopoietic cell transplant recipients and did not identify an increased risk among RZV recipients. One study among kidney transplant patients reported on graft rejection and did not identify an increased risk among RZV recipients. Local and systemic grade 3 reactions (reactions that interfere with daily activities) were evaluated in six studies in five immunocompromised groups. Local grade 3 reactions occurred in 10.7% to 14.2% of RZV recipients, and systemic grade 3 reactions occurred in 9.9% to 22.3% of RZV recipients. Systemic grade 3 reactions were also reported by 6.0% to 15.5% of placebo recipients in these studies.
Don’t delay giving the second dose of varicella vaccine. Give the second dose the next time the child is in your office. The recommendation to routinely give a second dose at age 4 through 6 years is intended to provide improved protection in the 15% to 20% of children who do not adequately respond to the first dose.
People who have had PCV13 and PPSV23 after the 65th birthday are not routinely recommended to receive additional doses of pneumococcal vaccine; however, they may receive a dose of PCV20 or PCV21 at least 5 years after their most recent pneumococcal vaccination based on shared clinical decision-making. The benefit of PPSV23 wanes after about 5 or more years. Considerations for PCV20 or PCV21 in this situation include the patient’s overall health and risk of pneumococcal disease, their desire to be protected, and time since last pneumococcal vaccination.
ACIP recommends vaccination against hepatitis A virus (HAV) infection for all previously unvaccinated people who anticipate having close personal contact with an international adoptee from a country of high or intermediate endemicity during the first 60 days following the adoptee’s arrival in the U.S. In addition to the adoptee’s new parents and siblings, this group might include grandparents, other household members, regular babysitters and other caregivers. The first dose of HepA should be given to close contacts as soon as adoption is planned, ideally at least 2 weeks before the arrival of the adoptee. A second dose should be given no sooner than 6 months after the first dose.
It is advisable to wait at least 4 weeks. Published studies have found that transient HBsAg-positivity can be detected for up to 18 days after HepB vaccination (up to 52 days among hemodialysis patients). This does not mean the person is infected with HBV. However, donating too close to receipt of HepB could cause a person to be permanently deferred from blood donation if that person tests transiently HBsAg positive after the vaccine dose.
A history of genital warts or clinically evident genital warts indicates previous infection with HPV, most often type 6 or 11, which cause 90% of genital warts. However, people with this history might not have been infected with both HPV 6 and 11 or with the other HPV types included in HPV vaccine. Vaccination will provide protection against infection with HPV serotypes the patient has not already acquired. Providers should advise their patients/clients that the vaccine will not have a therapeutic effect on existing HPV infection or genital warts. It is important, however, that patients receive a full age-appropriate series of HPV vaccine to get full protection from genital warts, in addition to the cancer-causing HPV types in the vaccine.
A precaution to Dengvaxia is a moderate or severe acute illness with or without fever. Vaccination should be deferred until the condition improves.
ACIP recommends that Dengvaxia may be used with precaution in certain special populations for whom the risks and benefits of vaccination to prevent DENV infection must be evaluated but for whom limited safety data are available. These groups include pregnant people, breastfeeding people, and people with HIV that is controlled and does not meet the criteria for a contraindication.
You are correct that vaccinated people can still develop measles if exposed even if they have been vaccinated, though it is uncommon. No vaccine is 100% effective. Vaccine effectiveness for one dose of MMR is 93% and 97% for 2 doses of MMR. Evidence suggests that people who were previously vaccinated and developed measles may have less severe disease and may be less contagious.
Both of these vaccines provide protection against diphtheria, tetanus, and pertussis. Boostrix (GSK) is licensed for people ages 10 years and older, and Adacel (Sanofi Pasteur) is licensed for people ages 10 through 64 years. The two vaccines also contain a different number of pertussis antigens and different concentrations of pertussis antigen and diphtheria toxoid.
First and foremost, rotate your vaccine supply so expensive vaccine does not expire in your refrigerator. If you discover expired vaccine, remove it from the refrigerator or freezer so that it is not inadvertently given to a patient. Expired vaccines and diluents should NEVER be administered, even if it is only 1 day past the expiration date. Contact your immunization program, vaccine supplier, or vaccine manufacturer for specific policies about disposing expired vaccines.
Yes. MenB vaccines work differently and receiving mismatched MenB doses might result in inadequate protection. For this reason, documentation of the brand of vaccine is especially important. The two MenB products are MenB-4C (Bexsero, GSK) and MenB-FHbp (in Trumenba and the Penbraya brand of MenABCWY, both by Pfizer). If a patient at high risk requires a booster dose and the brand of the primary series doses cannot be determined or is unavailable, then CDC recommends restarting the primary series with the available brand.
The first MenB booster dose is recommended one year following completion of the primary series, with subsequent MenB booster doses every 2–3 years thereafter, as long as risk remains.
If a record shows that Penbraya (MenABCWY, Pfizer) was administered to a patient subsequent MenB doses should be Trumenba (or Penbraya, if MenABCWY is indicated).
Heroin use or addiction of the mother is not a reason to delay vaccination of an otherwise healthy infant.
Steroid treatment, and possible immunosuppression, is primarily a concern with live virus vaccines. Steroid therapy that is short term (less than 2 weeks); alternate-day; physiologic replacement; topical (skin or eyes); aerosol; or given by intra-articular, bursal, or tendon injection are not considered contraindications to the use of live virus vaccines. The immunosuppressive effects of corticosteroid treatment vary, but many clinicians consider a dose equivalent to either 2 mg/kg of body weight or a total of 20 mg per day of prednisone (or equivalent) for 2 or more weeks as sufficiently immunosuppressive to raise concern about the safety of vaccination with live virus vaccines (e.g., MMR, varicella, live attenuated influenza, yellow fever). Providers should wait at least 1 month after discontinuation of therapy or reduction of dose before administering a live virus vaccine to patients who have received high systemically absorbed doses of corticosteroids for 2 weeks or more. Inactivated vaccines and toxoids can be administered to all immunocompromised patients in usual doses and schedules, although the response to these vaccines may be suboptimal.
Yes. Breastfeeding is not a contraindication for any routine vaccination including FluMist (LAIV).
Clinical trials of nirsevimab (Beyfortus, Sanofi) in infants less than 8 months old born during or entering their first RSV season showed that giving nirsevimab reduced the risk of RSV-associated lower respiratory tract infection (LRTI) requiring a medical visit or hospitalization by approximately 80 percent and reduced the risk of ICU admission for this reason by 90 percent.
Clinical trials did not study hospitalization rates among older infants and toddlers at high risk of severe RSV disease in their second RSV season. Instead, a study was done to measure blood levels of nirsevimab given to infants and toddlers at increased risk for severe RSV disease (certain preterm infants and those with serious heart or lung disease). The blood levels of nirsevimab were equivalent to the levels in healthy infants in the clinical trial who received nirsevimab in their first RSV season. Based on this finding, it is estimated that their protection from serious infection would also be similar.
Clesrovimab (Enflonsia, Merck) is a preventive antibody product approved in mid-2025 to be administered intramuscularly as a single 105 mg dose to infants from age 0 days to age 8 months and 0 days either before or during their first RSV season. It is recommended for use as an option for prevention of serious lower respiratory tract infection with RSV in infants. There is no preference between clesrovimab and nirsevimab (Beyfortus, Sanofi) for eligible infants. However, only nirsevimab is approved for high-risk children age 8 through 19 months entering their second RSV season.
Clinical trials demonstrated clesrovimab had benefits similar to nirsevimab, with a 60% reduced risk of medically attended lower-respiratory tract illness (MALRI) caused by RSV and an 84% reduced risk of hospitalization with RSV LRI during the 150 days after administration.
With rare exceptions, yes. Like other live vaccines, FluMist (LAIV) should not be administered to immunosuppressed people. ACIP has stated a preference for using injectable influenza vaccine for all close contacts of severely immunosuppressed individuals 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 (people who do not require a protective environment such as reverse isolation in a hospital setting) who are otherwise eligible for FluMist may receive it. No special precautions need to be taken by the vaccinated person.
The patient may be given one dose of PCV20 or PCV21. CDC estimates that PCV20 targets serotypes that cause approximately 54% of invasive pneumococcal disease (IPD) in people age 65 years and older in the United States and that PCV21 targets serotypes that cause approximately 85% of IPD cases in that U.S. age group. In some parts of the Western United States, pneumococcal serotype 4 is known to be responsible for more than 30% of IPD cases and state or local public health officials may advise healthcare providers that a product that covers serotype 4 (PCV20) may provide broader coverage than national estimates suggest. CDC does not recommend additional doses of PPSV23.
Timing of Shingrix vaccination should be evaluated on a case-by-case basis. When possible, patients should be vaccinated before becoming immunosuppressed. If vaccination before initiating immunosuppressive treatment is feasible, a shortened interval of 4 weeks between doses 1 and 2 may be considered. If vaccination before immunosuppression is not possible, providers should consider timing vaccination when the immune response is likely to be most robust.
For additional information about timing of zoster vaccination and specific conditions, see CDC’s Clinical Considerations for the Use of Recombinant Zoster Vaccines in Immunocompromised Adults Aged ≥ 19 Years: www.cdc.gov/shingles/hcp/vaccine-considerations/immunocompromised-adults.html.
Postvaccination serologic testing for varicella immunity is not recommended for any group, including healthcare personnel.
ACIP recommends a routine 2-dose HPV vaccine schedule for adolescents who start the vaccination series before the 15th birthday. The two doses should be separated by 6 to 12 months. The minimum interval between doses is 5 calendar months.
A 3-dose schedule is recommended for people who start the series on or after the 15th birthday and for people with certain immunocompromising conditions (such as cancer, HIV infection, or taking immunosuppressive drugs), regardless of their age at the time of the first dose. The second dose should be given 1 to 2 months after the first dose and the third dose 6 months after the first dose. The minimum interval between the first and second doses of vaccine is 4 weeks. The minimum interval between the second and third doses of vaccine is 12 weeks. The minimum interval between the first and third doses is 5 calendar months. If the vaccination series is interrupted, the series does not need to be restarted.
The January 2018 recommendations are available at www.cdc.gov/mmwr/volumes/67/rr/pdfs/rr6701-H.PDF.
The 2020 ACIP recommendations for the prevention of hepatitis A define a person experiencing homelessness as 1) a person who lacks housing (regardless of whether the person is a member of a family), including a person whose primary residence during the night is a supervised public or private facility (e.g., shelter) that provides temporary living accommodations and a person who is a resident in transitional housing, 2) a person without permanent housing who might: live on the streets, stay in a shelter, mission, single-room occupancy facility, abandoned building, vehicle, or any other unstable or nonpermanent situation, or 3) who is “doubled up”, a term that refers to a situation where persons are unable to maintain their housing situation and are forced to stay with a series of friends or extended family members. In addition, previously homeless persons who are to be released from a prison or a hospital might be considered homeless if they do not have a stable housing situation to which they can return. The instability of a person’s living arrangements is critical to the definition of homelessness.
It is acceptable to put the Beyond Use Date (BUD) on the packaging; this may help when reviewing inventory. But a provider should always read the label on the vial before administering a vaccine. It is possible for a vial to be placed in the wrong box. So, the vial label is the safest place to put the BUD. Vial labels are small, and it may require putting an extra sticky label on the vial.
Recommendations to separate MenACWY and PCV under certain circumstances only applied to MenACWY-D (Menactra, Sanofi), which is no longer available in the United States. So, you may administer any available and recommended MenACWY and PCV vaccines at the same time. A 10-year-old with persistent complement component deficiency also should receive a 3-dose series (the same product for all doses) of MenB vaccine.
As long as the child remains at high risk of meningococcal disease due to complement inhibitor use, booster doses of both MenACWY and MenB are recommended. A MenACWY booster dose should be given every 5 years and a MenB booster dose should be given one year after the completion of the primary series, followed by a booster dose every 2–3 years thereafter. If using MenB-FHbp (Trumenba, Pfizer), you have the option to use MenABCWY (Penbraya, Pfizer) when both MenACWY and MenB vaccinations are due at the same visit, as long as doses of Penbraya are separated by at least 6 months.
Because patients treated with complement inhibitors can develop invasive meningococcal disease despite vaccination, clinicians using Soliris, Ultomiris, Enjaymo, or other complement inhibitors also may consider antimicrobial prophylaxis for the duration of complement inhibitor therapy.
Vaccines received before starting chemotherapy generally do not need to be repeated after chemotherapy is completed. Chemotherapy does not negate vaccine-induced immunity. However, revaccination is recommended for people who are recipients of a hematopoietic cell transplant (HCT), such as a bone marrow transplant, because immunity present before the transplant is lost and may not be replaced by donor cells. For more information on this issue please refer to the Altered Immunocompetence section of the ACIP “General Best Practices Guidelines for Immunization” at www.cdc.gov/vaccines/hcp/imz-best-practices/timing-spacing-immunobiologics.html.
All live injected vaccines (MMR, varicella, and yellow fever) are recommended to be given subcutaneously (Subcut). In February 2023, FDA approved the administration of MMRII (Merck) brand of MMR by either Subcut or IM routes. The Priorix (GSK) brand of MMR is approved only for Subcut administration. Intramuscular (IM) administration of any of these live virus vaccines is not likely to decrease immunogenicity, and doses given IM do not need to be repeated. When administering MMRII by the IM route, select an appropriate needle length for the patient’s size. See Immunize.org’s clinical resource “Administering Vaccines: Dose, Route, Site, and Needle Size” at www.immunize.org/catg.d/p3085.pdf.
Administration of Dengvaxia to a person who has never been infected with DENV may result in an increased risk of hospitalization and severe dengue illness if they are infected with natural (wild type) DENV for the first time after vaccination.
Multiple complex mechanisms likely contribute to increased disease severity during a second DENV infection. The published ACIP recommendation provides a detailed description of these mechanisms at www.cdc.gov/mmwr/volumes/70/rr/pdfs/rr7006a1-H.pdf. In addition, CDC has developed simple illustrations and descriptions to explain this phenomenon at https://www.cdc.gov/dengue/hcp/vaccine/eligibility.html.
In a person who has never been infected with DENV, vaccination with Dengvaxia may “stand in” (immunologically) for the first natural infection, resulting in an increased risk of severe dengue in response to the first natural infection because the immune system responds as if that infection were the “second” infection.
Twinrix is an inactivated combination vaccine containing both hepatitis A virus (HAV) and HBV antigens. The vaccine contains 720 EL.U. of hepatitis A antigen (half of the Havrix adult dose) and 20µg of hepatitis B antigen (the full Engerix-B adult dose). In the U.S., Twinrix is licensed for use in people who are age 18 years or older. It can be administered to people who are at risk for both hepatitis A and hepatitis B, such as certain international travelers, people with chronic liver disease, men who have sex with men, illegal drug users, or to people who simply want to be immune to both diseases. A Twinrix series consists of 3 doses given intramuscularly on a 0, 1-, and 6-month routine schedule. For travelers who need protection quickly, four doses of Twinrix may be used to complete hepatitis A and hepatitis B vaccination, with the first three doses administered at 0, 7 days, and 21-30 days, and a booster dose at 12 months.
CDC discourages the practice of prefilling vaccine into syringes, primarily because of the increased possibility of administration and dosing errors. An exception may be considered when only a single type of vaccine is to be administered during a clinic (e.g., influenza). Another reason to discourage the practice in general is that some vaccines have a very limited shelf life after reconstitution. If the reconstituted vaccine is not used within the designated time period, it must be discarded. A chart of the time allowed between reconstitution and use, “Vaccines with Diluents: How to Use Them,” is available at www.immunize.org/catg.d/p3040.pdf. For more information on prefilling syringes, please read the 2011 Technically Speaking column written by Immunize.org founder, Dr. Deborah Wexler, www.immunize.org/about/pub-archives/guidance-for-busy-clinics-on-prefilling-your-own-syringes/.
Clinical trial results for the original monovalent Pfizer-BioNTech COVID-19 Vaccine (administered as a two-dose primary series) demonstrated that among vaccine recipients age 12–15 years, side effects during the 7 days after vaccination were commonly reported (90.9% of vaccine recipients reported a local reaction and 90.7% reported a systemic reaction). Most reactions were mild to moderate. Pain at the injection site was the most common local reaction. One in 10 reported a side effect that interfered with daily activities. Side effects usually resolved after 1–2 days. Systemic side effects (e.g., fever, fatigue, headache, muscle pain) were more commonly reported after the second dose than after the first dose. No specific safety concerns were identified among adolescent vaccine recipients.
The safety and side effects of the 2025–2026 formula are expected to be consistent with the previous formulations of the product.
