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.
No vaccine series needs to be restarted because of an interval that is longer than recommended (with the exception of oral typhoid vaccine in certain circumstances). You should resume the HPV vaccine series where it was interrupted.
ACIP recommends the following for the use of Tdap in healthcare personnel:
To view updated recommendations on the use of Td or Tdap in situations where only Td was previously recommended, go to www.cdc.gov/mmwr/volumes/69/wr/pdfs/mm6903a5-H.pdf. For details about Tdap and other recommendations for healthcare personnel, go to “Immunization of Health-Care Personnel” (MMWR 2011;60[SS-7]:4-46) at www.cdc.gov/mmwr/pdf/rr/rr6007.pdf.
No. IG may contain antibodies to measles, mumps, and rubella that could reduce the effectiveness of MMR vaccine. For this reason, in February 2018 ACIP voted to recommend that hepatitis A vaccine should be administered to infants age 6 through 11 months traveling outside the United States when protection against hepatitis A is recommended. MMR and hepatitis A vaccines may be safely co-administered to children in this age group. Neither vaccine is counted as part of the child’s routine vaccination series. For details of this recommendation, see the CDC ACIP recommendations for the prevention and control of hepatitis A at www.cdc.gov/mmwr/volumes/69/rr/pdfs/rr6905a1-H.pdf, page 18.
Twelve weeks. The spacing between doses of a combination vaccine depends on the longest minimum interval of a component. The minimum interval between doses of MMR is 4 weeks; the minimum interval between doses of varicella vaccine is 12 weeks for a child this age. So, you should wait 12 weeks between the doses of MMRV for the two doses to be valid.
In 2005, ACIP recommended routine MenACWY vaccination for all preteens at age 11 or 12 years to protect them from meningococcal disease when its incidence rises in the late teens and early 20s. Subsequent studies indicated that the protection provided by MenACWY waned within 5 years following vaccination. For this reason, in 2010, ACIP recommended a MenACWY booster dose at age 16 to provide continuing protection during the age of increased meningococcal incidence.
A CDC study showed 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. The risk for febrile seizures in children who received the currently-recommended PCV15 or PCV20 vaccines at the same time as an influenza vaccine has not been studied.
See www.cdc.gov/vaccine-safety/about/febrile-seizures.html for more information about febrile seizures after vaccination.
In rare circumstances, nirsevimab (Beyfortus, Sanofi) or clesrovimab (Enflonsia, Merck) may be considered for infants in their first RSV season who were born to RSV-vaccinated mothers. These situations may include:
Infants and children age 8 through 19 months who are at increased risk for severe RSV disease and are entering their second RSV season are recommended to receive nirsevimab (Beyfortus) regardless of history of maternal vaccination. Clesrovimab is not recommended for children age 8 months or older.
Hepatitis A vaccine (HepA) should be administered intramuscularly (IM), using the appropriate injection site and needle size as determined by the patient’s age and body mass. See Immunize.org’s clinical resource, “How to Administer Intramuscular and Subcutaneous Vaccine Injections” for details, www.immunize.org/catg.d/p2020.pdf.
According to CDC’s interim clinical considerations for the use of COVID-19 vaccines, whenever possible, COVID-19 vaccines should be administered at least 2 weeks before initiation or resumption of immunosuppressive therapies. For patients who receive B-cell-depleting therapies on a continuing basis, COVID-19 vaccines should be administered approximately 4 weeks before the next scheduled therapy.
CDC also notes that timing of COVID-19 vaccination should take into consideration current or planned immunosuppressive therapies, optimization of both the patient’s medical condition and response to vaccination, and individual benefits and risks. Review the CDC’s considerations for COVID-19 vaccination of those on immunosuppressive therapies here: www.cdc.gov/covid/hcp/vaccine-considerations/immunocompromised.html#cdc_cg_special_populations_about-considerations-for-timing-of-covid-19-vaccination-in-relation-to-immunosuppressive-therapies.
On a case-by-case basis, providers caring for these patients may administer COVID-19 vaccines outside of the FDA and CDC dosing schedules based on their clinical judgment of what is most beneficial to the patient.
ACIP routinely recommends nirsevimab (Beyfortus, Sanofi) or clesrovimab (Enflonsia, Merck) only for infants younger than 8 months of age whose mothers were not vaccinated, or not effectively vaccinated, with Abrysvo (Pfizer) RSV vaccine during their pregnancy. RSV preventive antibody products are not recommended for this infant unless there is a clinical reason to believe maternal vaccination was ineffective, for example, if the infant had been born less than 14 days after vaccine administration. See this question for additional information about when to consider an RSV preventive antibody product for the infant of a vaccinated mother.
No. Mesalamine (mesalazine) is a non-steroidal anti-inflammatory drug. It is not immunosuppressive, so its use would not place a person at increased risk of invasive pneumococcal disease.
Shingrix has not been evaluated for, and is not recommended for, the prevention of primary infection with varicella virus (chickenpox).
In this case, the patient is not yet immunocompromised and has no evidence of immunity to varicella. The simplest next step is to vaccinate the patient with two doses of varicella vaccine, spaced at least 4 weeks apart, before initiating immunosuppressing medication.
If you wish, you may order a commercial serologic assay to look for evidence of past varicella virus exposure. However, remember that the sensitivity and specificity of these tests vary, and while such commercial tests can detect evidence of past varicella infection, they are not sensitive enough to reliably detect evidence of past vaccination with varicella vaccine.
For patients who lack evidence of past infection or vaccination and who are immunocompromised already, CDC has provided additional detailed clinical considerations here: www.cdc.gov/shingles/vaccination/immunocompromised-adults.html#special-populations.
A booster dose should be given to first-year college students, regardless of age, who are or will be living in a residence hall if the previous dose was given before the age of 16 years or if their most recent dose (given after the 16th birthday) was not given within the past 5 years.
There is no minimum period to wait to correct your error. If you had immediately realized that you had mistakenly given the father-to-be Td instead of Tdap, you could have given him the needed Tdap dose at the same visit at which you gave him the erroneous Td dose.
The IDSA guidelines indicate that persons receiving rituximab should be considered to have high-level immunosuppression. Both inactivated and live vaccines should be withheld at least 6 months following treatment with lymphocyte depleting medications such as rituximab. As for the IG, the interval to live vaccination depends on the dose. For guidance, please refer to the Timing and Spacing of Immunobiologics section of CDC’s “General Best Practices Guidelines for Immunization”, table 3–6: “Recommended intervals between administration of antibody-containing products and measles- or varicella-containing vaccine, by product and indication for vaccination” at www.cdc.gov/vaccines/hcp/imz-best-practices/timing-spacing-immunobiologics.html. This interval could be as long as 11 months, depending on the dose he receives.
Yes. The second dose of MMR may be scheduled a minimum of 28 days after the first dose, if necessary.
HPV vaccine is not recommended for use during pregnancy. HPV vaccines have not been associated causally with adverse outcomes of pregnancy or adverse events in the developing fetus. However, if a person is found to be pregnant after initiating the vaccination series, the remainder of the series should be delayed until completion of pregnancy. Pregnancy testing is not needed before vaccination.
If a vaccine dose has been administered during pregnancy, no intervention is needed.
Yes. Other inactivated and/or live virus vaccines can be administered at the same time as HepA vaccine, but should be given at a different anatomical site, if possible. If given in the same muscle, separate the injections by a minimum distance of 1 inch.
HBsAg-negative infants with anti-HBs levels 10 mIU/mL or higher are protected and need no further medical management. HBsAg-negative infants with anti-HBs less than 10 mIU/mL should be revaccinated with a single dose of hepatitis B vaccine and receive postvaccination serologic testing 1–2 months later. Infants whose anti-HBs remains less than 10 mIU/mL following single dose revaccination should receive 2 additional doses of HepB to complete the second series, followed by postvaccination serologic testing 1–2 months after the final dose.
Based on clinical circumstances or family preference, HBsAg-negative infants with anti-HBs less than 10 mIU/mL may instead be revaccinated with a second, complete 3-dose series, followed by postvaccination serologic testing performed 1–2 months after the final dose of vaccine.
Findings of this study discourages the prophylactic use of paracetamol (which is similar to acetaminophen) before or immediately following vaccination. Acetaminophen may be used to treat pain or fever if either symptom should occur following vaccination. CDC’s “General Best Practices for Immunization” states: “Evidence does not support use of antipyretics before or at the time of vaccination; however, they can be used for the treatment of fever and local discomfort that might occur following vaccination. Studies of children with previous febrile seizures have not demonstrated antipyretics to be effective in the prevention of febrile seizures.” For more information on this issue, see Methods for Alleviating Discomfort and Pain Associated with Vaccination at www.cdc.gov/vaccines/hcp/imz-best-practices/vaccine-administration.html.
Yes. It is especially important to vaccinate during pregnancy because of the increased risk for influenza-related complications during pregnancy and the 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.
Vaccination can occur in any trimester, including the first. Only inactivated or recombinant influenza vaccines may be given during pregnancy. FluMist (LAIV), a live vaccine, should not be given during pregnancy.
In addition to the long-standing recommendation from ACIP, the American College of Obstetricians and Gynecologists (ACOG) strongly recommends influenza vaccination during pregnancy (www.acog.org/clinical/clinical-guidance/practice-advisory/articles/2025/08/influenza-in-pregnancy-prevention-and-treatment). The American Academy of Pediatrics (AAP) recommends influenza vaccination of all children, including pregnant teens. See the AAP policy statement on influenza vaccination for the 2025–26 season here: https://publications.aap.org/pediatrics/article/doi/10.1542/peds.2025-073620/202845/Recommendations-for-Prevention-and-Control-of.
Nirsevimab (Beyfortus, Sanofi) dosing is based upon weight and/or age. It is available in 50-mg or 100-mg manufacturer-filled syringes (MFS). Infants younger than 8 months and weighing less than 5 kgs (11 lbs.) should receive a 50-mg dose, given as a 50-mg MFS. Infants younger than 8 months and weighing 5 kg (11 lb.), or more, should receive a single 100-mg dose, given as a 100-mg MFS. Infants and toddlers age 8 months through 19 months who need nirsevimab should receive a 200-mg dose, given as two 100-mg MFS.
Avoid administering two 50-mg MFS to an infant who needs a 100-mg MFS. The 50-mg MFS is intended for the smallest infants. The cost of the 50-mg and 100-mg MFS are equivalent, despite the difference in dose; insurance plans may not cover the cost of two doses given to an infant not recommended to receive two doses. Only high-risk children age 8 through 19 months are recommended to receive two (100-mg) MFS doses at the same visit.
See the Immunize.org standing order template for details: www.immunize.org/wp-content/uploads/catg.d/p3097.pdf.
CDC states that no additional medical documentation is required before administering COVID-19 vaccine. The patient’s self-attestation of a high-risk condition, including moderate or severe immunocompromise, is sufficient. Those who report moderate or severe immunocompromise should be offered the modified schedule for people with moderate or severe immunocompromise. Vaccinators should not deny COVID-19 vaccination to a person due to lack of documentation of a self-reported high-risk condition.
Multiple sclerosis is not a contraindication to any vaccine, including pneumococcal vaccines.
People with multiple sclerosis may be on immunosuppressive medication. If so, immunosuppressed people should receive PCV20 or PCV21 alone or PCV15 followed by PPSV23 a minimum of 8 weeks later.
For additional details, see www.cdc.gov/pneumococcal/hcp/vaccine-recommendations/risk-indications.html.
No. Antiretroviral treatment for HIV may improve immune response to vaccination; however, zoster vaccination with Shingrix does not have to be delayed in order to achieve viral suppression, especially if this will significantly delay vaccine administration. Patients with advanced HIV should receive Shingrix, because the risk of shingles is further increased in the setting of such immune compromise.
In the case of an expired live vaccine, the issue is not necessarily the routine minimum interval (three months in the case of varicella and ProQuad vaccines), but the interval that would prevent viral interference if the expired vaccine happened to be still viable. This interval is considered to be four weeks (28 days). The repeat dose should be administered four weeks after the expired dose.
You should withhold further HPV vaccine until she is no longer pregnant. After the pregnancy is completed, administer the remaining doses of the series using the usual 2- or 3-dose schedule (depending on the age at initiation of the series).
Yes. ACIP recommends a dose of Tdap be given to all adults, including those age 65 years or older.
Yes, VFC-supported HepA vaccine is available for children 12 months through 18 years who are VFC-eligible. In addition, combination HepA and HepB vaccine (Twinrix; GSK) is also available for people who are age 18 years who are VFC-eligible.
No. A measles-containing vaccine administered more than 4 days before the first birthday should not be counted as part of the series. MMR should be repeated when the child is age 12 through 15 months (12 months if the child remains in an area where disease risk is high). The second dose should be administered at least 28 days after the first dose.
The ACIP’s varicella vaccine recommendations state that no adverse events associated with the use of salicylates after varicella vaccination have been reported, however, the vaccine manufacturer recommends that vaccine recipients avoid using salicylates for 6 weeks after receiving varicella vaccines because of the association between aspirin use and Reye syndrome after varicella disease (chickenpox). Vaccination with subsequent close monitoring should be considered for children who have rheumatoid arthritis or other conditions requiring therapeutic aspirin. The risk for serious complications associated with aspirin is likely to be greater in children in whom natural varicella develops than it is in children who receive the vaccine containing attenuated varicella zoster virus. In other words, the benefit of varicella vaccine likely outweighs the theoretical risk of Reye syndrome. See the ACIP varicella recommendations at www.cdc.gov/mmwr/PDF/rr/rr5604.pdf, page 29.
Available data do not suggest a benefit from administering additional HepB vaccine doses to infants who have not attained anti-HBs of mIU/mL or higher following receipt of two complete HepB series. HBsAg-positive infants should be referred for appropriate follow-up with a physician who specializes in evaluating infants with liver disease.
All providers who administer vaccinations should be aware of the potential for syncope (fainting) after vaccination and take appropriate measures to prevent it. Thus, clinicians should (1) make sure that people who are being vaccinated are always seated or lying down; (2) be aware of symptoms that precede fainting (weakness, dizziness, pallor, etc.); and (3) take appropriate measures to prevent injuries if such symptoms occur.
Immunize.org has two clinical resources specifically addressing vaccination-related syncope:
These two resources are also relevant:
CDC studies have shown that about 80% of fainting episodes occur within 15 minutes of receiving the vaccine. Vaccine providers should strongly consider observing vaccinated people for 15 minutes after vaccination in accordance with CDC’s General Best Practices for Immunization (see www.cdc.gov/vaccines/hcp/imz-best-practices/vaccine-administration.html). This is particularly important when vaccinating adolescents and young adults or those with a history of injection-related syncope. CDC has posted additional information on this topic at www.cdc.gov/vaccinesafety/concerns/fainting.html.
Yes. Doses of MenACWY given before 10 years of age should not be counted as part of the series. If a child received a dose of MenACWY before age 10 years, they should receive a dose of MenACWY at 11 or 12 years and a booster dose at age 16 years. A dose of MenACWY administered at age 10 may count as the first adolescent dose normally given at 11 or 12.
ACIP has recommended vaccinating during pregnancy with inactivated influenza vaccine since 1997. Studies have shown that pregnant people 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.
Infants younger than 6 months old are at high risk of influenza-related complications, but influenza vaccine is not recommended for them because the immune response to influenza vaccination is limited before 6 months of age. Vaccinating during pregnancy provides maternal antibodies to the fetus which helps protect infants against influenza during the first 6 months of life until they can get vaccinated at age 6 months. Vaccinating pregnant people protects them, their unborn babies, and their babies after birth.
The 50-mg manufacturer-filled syringes (MFS) of nirsevimab (Beyfortus) should be reserved for infants weighing less than 5 kilograms (less than 11 pounds). The cost of a single MFS is the same, whether it is a 50-mg MFS or a 100-mg MFS. Insurers are likely to cover only the cost of one MFS dose to an infant younger than age 8 months. Only high-risk children age 8 through 19 months are recommended to receive two (100-mg) MFS doses at the same visit.
Immunocompromised people who require an initial series of 3 doses of mRNA COVID-19 vaccine or two doses of Nuvaxovid (Sanofi-Novavax) adjuvanted protein COVID-19 vaccine should receive the initial series using COVID-19 vaccines from the same manufacturer, unless it is not feasible. If the same manufacturer cannot be used for all primary series doses (e.g., the brand is unavailable at the time of the vaccination visit, the previous brand is unknown, or the patient would not be vaccinated with the previous brand due to a contraindication or other reason), then administer another age-appropriate brand. Spikevax (Moderna) is the only licensed 2025–2026 Formula COVID-19 vaccine option for children younger than age 5 years. If the immunocompromised recipient is age 5 years or older, once the initial series is complete, any appropriate brand may be used for all subsequent doses. Spikevax and mNexspike are interchangeable: both vaccines are made by Moderna.
This question has arisen more frequently since the introduction of the RSV preventive antibody, nirsevimab (Beyfortus, Sanofi), which has an injection volume of 1 mL for infants younger than age 8 months who weigh 5 kg or more at the time of immunization. High-risk children entering their second RSV season require a Beyfortus dose volume of 2 mL. Beyfortus is often administered at a routine visit when other infant immunizations are due.
There is no specific guidance to not exceed 1 mL in one muscle. In fact, there is no clear standard of practice and reference texts vary in guidance. Facilities or health systems may have medication policies/procedures that outline guidance for their staff. Professional judgement is needed when administering intramuscular medications or immunizations to people, including children, because muscle size varies from person to person.
CDC experts suggest a range of volume, depending upon the muscle injected. For the deltoid, the typical volume injected is 0.5 mL (maximum: 2 mL). For the vastus lateralis (the thigh): the typical volume that may be injected is 1–4 mL (maximum: 5 mL). Infants and toddlers fall at the lower end of these ranges, whereas adolescents and adults generally fall on the higher end of the range.
If more than 1 mL of volume needs to be injected into the thigh, that can be done while staying well within the acceptable range. Use of combination vaccines, when indicated and available, can decrease injection volume.
Studies done in children showed possible interference with the response to PCV7 when PCV7 and the Menactra brand of MenACWY-D (by Sanofi) were given simultaneously. For this reason, Menactra was recommended not to be given at the same time as PCV. However, Menactra is no longer available, so this is no longer a consideration.
Available brands of MenACWY, including MenACWY-CRM (Menveo, GSK), MenACWY-TT (MenQuadfi, Sanofi), as well as the pentavalent MenABCWY (Penbraya, Pfizer), may be administered at the same time or any time before or after any pneumococcal vaccine.
In pre-licensure clinical trials of Shingrix in immunocompetent adults age 50 years or older, the most common adverse reactions were pain at the injection site (78%), myalgia (45%), and fatigue (45%). Any grade 3 adverse event (reactions related to vaccination which were severe enough to prevent normal activities) was reported in 17% of vaccine recipients compared with 3% of placebo recipients. Grade 3 injection-site reactions (pain, redness, and swelling) were reported by 9% of vaccine recipients, compared with 0.3% of placebo recipients. Grade 3 solicited systemic events (myalgia, fatigue, headache, shivering, fever, and gastrointestinal symptoms) were reported by 11% of vaccine recipients and 2.4% of placebo recipients. The occurrence of local grade 3 reactions did not differ by vaccine dose. However systemic grade 3 reactions were reported more frequently after dose 2.
Rates of serious adverse events (an undesirable experience associated with the vaccine that results in death, hospitalization, disability or requires medical or surgical intervention to prevent a serious outcome) were similar in vaccine and placebo groups.
Among immunocompromised recipients of Shingrix, local grade 3 reactions occurred in 10.7% to 14.2% of recipients, and systemic grade 3 reactions occurred in 9.9% to 22.3% of recipients, compared with 0% to 0.3% and 6.0% to 15.5%, respectively, among placebo recipients. Limited studies have found no evidence of an increased risk of immune-mediated diseases, graft-versus-host-disease, or transplant rejection among certain categories of immunocompromised Shingrix recipients.
ACIP recommends the following:
You do not need to start the series over again. The immunogenicity of 1 dose of HepA vaccine is 94% to 100%; studies have shown persistent protection from a single dose lasting more than 10 years. To ensure optimal long-term protection it is important to administer the second dose.
Yes. A TST can be applied before or on the same day that MMR vaccine is given. However, if MMR vaccine is given on the previous day or earlier, the TST should be delayed for at least 28 days. Live measles vaccine given prior to the application of a TST can reduce the reactivity of the skin test because of mild suppression of the immune system.
This is not necessary unless the person who was vaccinated develops a rash.
Yes. An HBsAg-positive mother who wishes to breastfeed should be encouraged to do so, including immediately following delivery. However, the infant should receive HBIG and HepB vaccine within 12 hours of birth. Although HBsAg can be detected in breast milk, studies done before HepB was available showed that breastfed infants born to HBsAg-positive mothers did not demonstrate an increased rate of perinatal or early childhood HBV infection. More recent studies have shown that, among infants receiving post-exposure prophylaxis to prevent perinatal HBV infection, there is no increased risk of infection among breastfed infants.
Yes, administration of a different inactivated or live vaccine, either at the same visit or at any time before or after HPV vaccine, is acceptable because HPV is not a live vaccine.
Diluents are not interchangeable, except for the sterile water used in Merck’s measles-mumps-rubella (MMR), measles-mumps-rubella-varicella (MMRV), and varicella vaccines. No other diluent can be used for these vaccines, and these diluents must not be used to reconstitute any other lyophilized vaccine.
If the wrong diluent is used, the vaccination should always be repeated. If an inactivated vaccine is reconstituted with the wrong diluent and is administered, the dose is invalid and should be repeated as soon as possible. If a live vaccine is reconstituted with the wrong diluent and is administered, the dose is invalid. If the dose can’t be repeated on the same clinic day, it needs to be repeated no earlier than four weeks after the invalid dose. This spacing is due to the effects of generating a partial immune response that could suppress the live replication of subsequent doses, even of the same live vaccine.
Immunize.org has produced a printable document with details about vaccines that require diluents and how to use them: www.immunize.org/wp-content/uploads/catg.d/p3040.pdf.
Yes, however, this issue is not addressed in the 2010 MMRV ACIP recommendations. Although this is off-label use, CDC recommends that when a dose of MMRV is inadvertently given to a patient age 13 years or older, it may be counted towards completion of the MMR and varicella vaccine series and does not need to be repeated.
ACIP recommends routine booster doses of MenACWY for people two months old or older at ongoing high risk for meningococcal infection (see www.cdc.gov/mmwr/volumes/69/rr/pdfs/rr6909a1-H.pdf, Table 3). This group includes people (1) with persistent complement component deficiency (an immune system disorder) or who take a complement inhibitor (examples include eculizumab [Soliris], ravulizumab [Ultomiris], and sutimlimab [Enjaymo]), (2) with anatomic or functional asplenia, (3) with HIV infection, (4) who have higher risk of exposure (including microbiologists who handle Neisseria meningitidis isolates and travelers to or residents of areas with epidemic or hyperendemic meningococcal disease [such as the meningitis belt of sub-Saharan Africa]).
Children at continued high risk who received the last dose of the primary series of MenACWY before age 7 years should receive the next dose 3 years after the most recent dose, then every 5 years as long as risk remains. People at continued high risk who received the last dose of the primary series at age 7 years or older should receive the next dose 5 years after the most recent dose then every 5 years as long as risk remains. Menveo (MenACWY-CRM) is licensed through age 55 years; however, if MenQuadfi (MenACWY-TT, licensed for use at age 2 years and older) is unavailable for an adult age 56 years or older, you may use Menveo.
Yes, nirsevimab (Beyfortus, Sanofi) or clesrovimab (Enflonsia, Merck) may be coadministered with all other recommended age-appropriate vaccines. An RSV preventive antibody product should not interfere with the immune response to routine childhood vaccines when given together or at any time before or after them. Likewise, vaccination does not interfere with the effectiveness of the preventive antibody product.
When giving several injections at a single visit, separate intramuscular vaccines by at least 1 inch in the body of the muscle, if possible, to reduce the likelihood of overlapping local injection site reactions.
Pregnant patients may receive any age-appropriate inactivated or recombinant influenza vaccine. The ACIP recommends use of influenza vaccines in single-dose vials or manufacturer-filled syringes. FluMist (LAIV) should not be given during pregnancy because it is a live virus vaccine.
In June 2025, ACIP voted to no longer recommend the use of influenza vaccines from multidose vials containing thimerosal as a preservative for any person. There is no evidence that the low doses of thimerosal contained in vaccines cause harm, unless the recipient has a rare severe allergy to thimerosal.
The American College of Obstetricians and Gynecologists (ACOG) strongly recommends vaccination with an inactivated or recombinant influenza vaccine during pregnancy, and makes no specific comment on thimerosal. The American Academy of Pediatrics (AAP) recommends seasonal vaccination of all children, beginning at age 6 months, including pregnant teens. AAP states, “Any licensed influenza vaccine appropriate for age and health status can be administered, as soon as possible in the season, without preference for one product or formulation.” See the AAP policy statement on influenza vaccination for the 2025–26 season.
The patient’s initial series is considered complete following a single dose of the Janssen COVID-19 Vaccine. People who are moderately or severely immunocompromised and have completed an initial series (no matter how long ago) should now receive 1 dose of an age-appropriate 2025–2026 Formula COVID-19 vaccine (at least 8 weeks after their most recent dose of a previous formulation). They should receive a second 2025–2026 Formula COVID-19 vaccine dose 6 months later (minimum interval 2 months for Comirnaty, Spikevax, and Nuvaxovid; minimum interval of 3 months if using mNexspike).
In the absence of immunosuppressive treatment, a recent history of prostate cancer surgery alone is not an indication for pneumococcal vaccination among people younger than 50 years.
Yes, people should receive additional booster doses (every 5 years) if they continue to be at increased risk for meningococcal ACWY infection.
A person should receive the dosage of HepA vaccine appropriate for their age at the time of administration. You should give the patient one adult dose of HepA to complete the 2-dose series. It is not necessary to restart the vaccine series.
Before vaccination, providers should counsel Shingrix recipients about common expected systemic and local adverse reactions (see related question). Reactions to the first dose do not strongly predict reactions to the second dose.
If a patient experiences side effects, any local (e.g., redness, pain, swelling at the injection site) or systemic (e.g., fever, chills, headache, body aches) reactions typically go away within 72 hours after vaccination. It is generally not recommended to take medication for pain or fever (e.g., acetaminophen or ibuprofen) before vaccination; however, such medications may be taken to alleviate local or systemic symptoms after vaccination, if needed. Shingrix recipients should be encouraged to complete the series even if they experienced a grade 3 reaction to the first dose.
This student should receive two doses of MMR, separated by at least 28 days. A personal history of measles and mumps is not acceptable as proof of immunity. Acceptable evidence of measles and mumps immunity includes a positive serologic test for antibody, birth before 1957, or written documentation of vaccination. For rubella, only serologic evidence or documented vaccination should be accepted as proof of immunity. Additionally, people born prior to 1957 may be considered immune to rubella unless they are women who have the potential to become pregnant.
Yes. No data exist on the efficacy or safety of HPV vaccine given by the Subcut route. All data on efficacy and duration of protection are based on a vaccine series administered by the IM route. In the absence of data on Subcut administration, CDC and the manufacturer recommend that a dose of HPV vaccine given by any route other than IM should be repeated. There is no minimum interval between the invalid (Subcut) dose and the repeat IM dose.
No. It is also unnecessary to change the needle if it has passed through two stoppers, which is done when a lyophilized vaccine is reconstituted. Changing needles is a waste of resources and increases the risk of needle stick injury.
There is no upper age limit for Tdap vaccination. A dose of Tdap is recommended for all adults. In addition, Tdap may be administered in any situations where Td only was previously recommended.
ACIP recommends varicella vaccine for healthy household contacts of pregnant people and immunosuppressed people. Although there may be a small risk of transmission of varicella vaccine virus to household contacts, the risk is much greater that the susceptible child will be infected with wild-type varicella, which could present a more serious threat to household contacts.
