Ask the Experts: All Questions

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.

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Results (1317)

Timing of 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 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/vaccination/immunocompromised-adults.html#clinical-guidance.

Last reviewed: March 9, 2022

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.

Last reviewed: February 16, 2022

Asthma is a precaution for FluMist in people 5 years of age and older. FluMist is contraindicated for children 2 through 4 years old who have had a diagnosis of asthma or whose parents or caregivers report that a health care provider has told them during the preceding 12 months that their child had wheezing or asthma or whose medical record indicates a wheezing episode has occurred during the preceding 12 months.

Last reviewed: September 10, 2023

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 injectable influenza vaccine. All inactivated influenza vaccines and recombinant influenza vaccine (Flublok Quadrivalent) may be administered at any time relative to antiviral medication.

Last reviewed: September 10, 2023

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.

Last reviewed: September 10, 2023

The dose should be repeated. If the error was detected on the same clinic day, you can repeat the dose that day. If the error is detected more than one day later and if the expired dose is a live virus vaccine, you must wait at least 28 days after the previous (expired) dose was given before repeating it. If the expired dose is not a live vaccine, the dose should be repeated as soon as possible. An exception to this is for recombinant zoster vaccine (Shingrix, GSK); the repeat dose should be given 4 weeks after the invalid dose, to reduce the risk of side effects caused by the adjuvant used to enhance the effectiveness of this vaccine. If you prefer, you can perform serologic testing to check for immunity for certain vaccinations (e.g., measles, rubella, hepatitis A, diphtheria, varicella, and tetanus).

Last reviewed: July 26, 2023

Yes. Studies from the United States, South Africa, and the United Kingdom have shown that people with HIV infection have a risk of invasive meningococcal disease that is 11–24 times higher than the general population. In the United States, this excess risk is specifically for serogroups C, W, and Y. ACIP recommends routine MenACWY vaccination of all HIV-infected people 2 months of age and older. Children younger than age 2 years should be vaccinated using a multidose schedule based upon age (see the Immunize.org document “Meningococcal ACWY Vaccine Recommendations by Age and Risk Factor,” available at www.immunize.org/catg.d/p2018.pdf for details).

People age 2 years and older with HIV infection who have not been previously vaccinated should receive a 2-dose primary series of MenACWY (doses separated by at least 8 weeks). People with HIV infection who have previously received one dose of MenACWY should receive a second dose at the earliest opportunity (at least 8 weeks after the previous dose) and then receive booster doses at the appropriate intervals (see Booster Doses below). ACIP does not recommend routine meningococcal serogroup B vaccination of people with HIV infection.

Last reviewed: March 24, 2024

Varicella postvaccination serologic testing is not recommended; however, if a person tests positive for varicella antibody 28 days or more after vaccination, the Advisory Committee on Immunization Practices (ACIP) considers the person to be immune. Studies have shown that a second dose boosts antibody titers and indicators of cell-mediated immunity significantly above the levels produced by a single dose. A second dose may be required to comply with school entry or institutional immunization requirements, regardless of serologic test results. You can access the ACIP varicella vaccine recommendations, which include evidence of immunity (page 16) at www.cdc.gov/mmwr/pdf/rr/rr5604.pdf.

Last reviewed: September 5, 2023

No. All adults age 65 years and older without a prior PCV vaccination are now routinely recommended to receive either PCV20 alone or a 2-dose series of PCV15 followed by PPSV23 one year later. People in this age group with an immunocompromising condition, cochlear implant, or cerebrospinal fluid leak who are given PCV15 may receive PPSV23 as little as 8 weeks later. PCV13 is no longer recommended for adults; however, CDC states that in rare situations where no PCV15 or PCV20 is available and a patient is otherwise unlikely to be vaccinated, an available dose of PCV13 may be used.

Last reviewed: April 5, 2024

Yes. A 5/8″ needle is recommended for subcutaneous injections for people of all sizes. See Immunize.org’s clinical resource “How to Administer Intramuscular and Subcutaneous Vaccine Injections” at www.immunize.org/catg.d/p2020.pdf.

Last reviewed: June 19, 2023

In general, a vaccine should not be prepared until the provider is ready to administer it to a patient. This is because once the syringe cap is removed or a needle is attached, the sterile seal is broken. However, if a sterile seal has been broken, staff should be sure to maintain the syringe at the appropriate temperature and either use it or discard it at the end of the clinic day. This issue is addressed in the CDC Storage and Handling Toolkit, available at www.cdc.gov/vaccines/hcp/admin/storage/toolkit/storage-handling-toolkit.pdf, page 20.

Last reviewed: December 28, 2022

Yes, it is. Infants and toddlers eligible for the VFC program may receive nirsevimab when recommended in the same way and in the same facilities where they receive VFC vaccines. Providers who participate in VFC should follow all VFC requirements for ordering, storage, and administration established by their state immunization program.

Last reviewed: January 22, 2024

Yes. The 2023–2024 formula Novavax vaccine is an option for any person age 12 years or older who is unvaccinated or was previously vaccinated with any COVID-19 vaccine and is due for a 2023–2024 updated vaccination. Any person age 12 years or older who has never had a dose of COVID-19 vaccine should receive two doses of Novavax vaccine, administered 3 to 8 weeks apart as a primary series.

Adults age 65 years or older who are not immunocompromised and who did not require a 2-dose primary series with the current 2023–2024 Formula are recommended to receive one additional dose of the current 2023–2024 Formula at least 4 months after the first 2023–2024 Formula dose; those who did require a 2-dose primary series this season should get a third dose at least 4 months following completion of the primary series.

Novavax recipients with moderate to severe immunocompromise being vaccinated for the first time may receive a third dose at least 2 months following the second dose in their primary series and may receive subsequent additional doses at the discretion of their healthcare provider, in consideration of their individual circumstances.

Additional details from FDA are available: www.fda.gov/vaccines-blood-biologics/coronavirus-covid-19-cber-regulated-biologics/novavax-covid-19-vaccine-adjuvanted.

Last reviewed: March 19, 2024

The most frequently reported side effects among vaccine recipients in the clinical trials were headache (40%), injection site pain (32%), malaise (25%), fatigue (25%), and muscle aches (29%).

As with any vaccine, healthcare providers should report any clinically significant adverse event to the Vaccine Adverse Events Reporting System (VAERS) at www.vaers.hhs.gov. even if a causal relation to vaccination is unknown or not certain.

Last reviewed: February 16, 2022

No. In March 2014, FDA lowered the age indication for Adacel brand Tdap vaccine (Sanofi) from age 11 years to age 10 years. Both Tdap products, Adacel and Boostrix (GSK), now have the same lower age indication.

Last reviewed: March 31, 2022

While a complete series of HepA is recommended for long-term protection, even a single dose of HepA vaccine has been demonstrated to provide protection against hepatitis A for more than 10 years and can prevent or control outbreaks of hepatitis A. People who are experiencing homelessness may have difficulty protecting themselves from exposure to HAV in other ways because of their living conditions. They should be vaccinated when possible and provided a record of immunization. Reporting the HepA vaccination to a state immunization information system also can facilitate immunization assessment at future healthcare encounters.

Last reviewed: June 25, 2023

Yes; people who are identified as being at risk for HBV infection during pregnancy should be vaccinated. They also should be counseled concerning other methods to prevent HBV infection. Providers should administer an age-appropriate 3-dose series of Twinrix, Engerix-B or Recombivax HB.

Until safety data are available for Heplisav-B or PreHevbrio administration during pregnancy, ACIP does not recommend the use of either of these products to vaccinate during pregnancy. Pregnancy testing prior to administration of these products is not recommended.

Last reviewed: July 21, 2023

Minimum intervals for Twinrix are 4 weeks between dose #1 and dose #2, and 5 months between dose #2 and dose #3.

Last reviewed: July 15, 2023

Yes. Household contacts and other close contacts of people who are immunocompromised (due to a disease, or treatment for a disease) should receive all routinely recommended vaccines, with the exception of smallpox vaccine. The live MMR, varicella, and rotavirus vaccines should be administered to susceptible household contacts and other close contacts of immunocompromised patients when indicated. MMR vaccine viruses are not transmitted to contacts, and transmission of vaccine strain varicella-zoster virus is rare. No specific precautions are needed unless the varicella vaccine recipient has a rash after vaccination, in which case direct contact with susceptible immunocompromised household contacts should be avoided until the rash resolves. All members of the household should wash their hands after changing the diaper of an infant who received rotavirus vaccine. This minimizes rotavirus transmission, as shedding may occur up to one month after the last dose.

Household and other close contacts of immunocompromised persons should receive annual influenza vaccination. Introduction of low levels of vaccine viruses into the environment likely is unavoidable when administering quadrivalent live attenuated influenza vaccine (LAIV4; Flumist, Medimmune). LAIV4 vaccine viruses are cold-adapted so they can replicate in the nose and generate an immune response without entering the lungs (that is, they are temperature sensitive and replicate poorly at core body temperatures). No instances have been reported of illness caused by attenuated vaccine virus infections among healthcare providers or immunocompromised patients. LAIV may be administered to healthy nonpregnant household and other close contacts of immunocompromised people unless the immunocompromised person is hospitalized in a protective environment, typically defined as a specialized patient-care area with a positive airflow relative to the corridor, high-efficiency particulate air filtration, and frequent air changes. A person who is administered LAIV4 should not have contact with an immunocompromised person in this type of protective environment for 7 days after administration.

Last reviewed: August 29, 2022

ACIP recommends annual influenza vaccination for all children age 6 months and older who do not have a contraindication to the vaccine.

Last reviewed: September 10, 2023

People who have neither experienced primary varicella infection (chickenpox), nor received live-attenuated varicella vaccine (vaccine strain VZV, contained in Varivax, ProQuad, and Zostavax, all by Merck) are not at risk for shingles. More than 99% of Americans born before 1980 have had chickenpox, even if they don’t remember it, so additional screening is not recommended for immunocompetent people born before 1980 who are due for routine shingles vaccination. Children and adolescents who have received live-attenuated varicella vaccines (Varivax or ProQuad) are at risk for shingles, although they are at lower risk for shingles than are those who experienced chickenpox.

Shingrix (RZV) is not indicated and has not been studied for the prevention of chickenpox. Receipt of Shingrix is not considered proof of varicella immunity, and Shingrix cannot be considered as either of the two doses of the varicella vaccine series. In addition, there are limited data on the use of Shingrix in people without a history of chickenpox, with or without a history of varicella vaccination.

The consequences of primary varicella infection in immunocompromised adults can be severe. For adults who are or will be immunocompromised, evidence of immunity to varicella (confirming need for RZV) includes:

  • Documentation of two doses of varicella vaccine, or
  • Laboratory evidence of immunity or laboratory confirmation of disease, or
  • Diagnosis or verification of a history of varicella or herpes zoster by a healthcare provider.

Protection from primary varicella infection (chickenpox) is a priority for an adult who is or will be immunocompromised with no evidence of immunity to chickenpox. Refer to the ACIP varicella vaccine recommendations for further guidance, including post-exposure prophylaxis guidance for immunocompromised adults: www.cdc.gov/mmwr/preview/mmwrhtml/rr5604a1.htm.

Last reviewed: March 9, 2022

Yes. ACIP recommends the 2-dose schedule for people starting the HPV vaccination series before the 15th birthday, as long as they are immunocompetent.

Last reviewed: March 2, 2024

There are now five inactivated influenza vaccine options for children younger than age 3 years.

Cell-culture-based Flucelvax Quadrivalent (ccIIV4, CSL Seqirus) is available to children beginning at age 6 months: administer 0.5 mL/dose intramuscularly (IM).

There are four egg-based quadrivalent inactivated influenza vaccines (IIV4s), all given as IM injections, available for children age 6 through 35 months:
•  Afluria Quadrivalent (CSL Seqirus): 0.25 mL/dose
•  Fluarix Quadrivalent (GSK): 0.5 mL/dose
•  FluLaval Quadrivalent (GSK): 0.5 mL/dose
•  Fluzone Quadrivalent (Sanofi): 0.25 mL or 0.5 mL per dose

Last reviewed: September 10, 2023

In clinical trials and in postlicensure safety surveillance, the most common local adverse events within 7 days of receiving MenB were injection site pain, swelling or redness and the most common systemic symptoms were headache, fatigue and body aches. In general, these types of self-limited reactions are reported more frequently than with MenACWY vaccination.

Last reviewed: March 24, 2024

It is not necessary to restart the MenACWY series. Give the person one dose of MenACWY vaccine now. This dose represents a delayed second dose in the primary series (a 2-dose primary series recommended for people with HIV infection). The patient will subsequently need booster doses every 5 years.

Last reviewed: March 24, 2024

There are various requirements for the use of vaccines after reconstitution. Some manufacturers’ package inserts require that the vaccine be used or discarded in varying time frames ranging from 24 hours after reconstitution to “immediately” after reconstitution. While the specific timeframes are simple to interpret, there can be some confusion as to what the requirement of “immediately” actually means.

CDC considers “immediately” to be the reasonable time it takes to prepare and transport the vaccine to the patient to be administered. This would include any limited documentation that may be related to this process. It is up to the judgment of a provider to determine if a vaccine has not been used in the appropriate time. Some manufacturers have indicated to providers that “immediately” can be up to 30 minutes. The definition of “immediately” varies from manufacturer to manufacturer. Some do not have the data to put forth a general timeframe as to what “immediately” means. CDC recommends that the provider contact the manufacturer if any question arises about whether or not a vaccine dose has been used in the appropriate timeframe.

Last reviewed: July 26, 2023

No. All adults for whom pneumococcal vaccination is recommended due to age (65 or older) or an underlying condition (age 19 through 64) are now recommended to receive a pneumococcal conjugate vaccine. Prior recipients of PPSV23 alone may now receive either PCV20 or PCV15 at least 1 year after the dose of PPSV23.

Last reviewed: April 5, 2024

Removing the protective cap increases the likelihood the septum or stopper could be punctured. The puncture may not be visible. It is important to ensure that the rubber seal on single-dose vials is not punctured because single-dose vials do not contain a preservative. Once the protective cap has been removed, the vaccine should be discarded at the end of the workday because it may not be possible to determine if the rubber seal has been punctured. For additional details, see CDC’s Vaccine Storage & Handling Toolkit at www.cdc.gov/vaccines/hcp/admin/storage/toolkit/storage-handling-toolkit.pdf.

Last reviewed: December 28, 2022

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 age 8 years 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.

Immunize.org’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.

Last reviewed: September 10, 2023

ACIP recommends one dose of nirsevimab (Beyfortus, Sanofi) preventive antibody for all infants less than 8 months and 0 days of age who are born during or entering their first RSV season.

ACIP also recommends one dose of nirsevimab for specific groups of infants and children age 8 through 19 months who are entering their second RSV season and at increased risk for severe RSV disease.

Children 8 through 19 months at high risk and ineligible for palivizumab:

  • American Indian or Alaskan Native children entering their second RSV season. This is especially important for those who are in remote regions or in communities known to have increased rates of severe RSV disease in children.

Children age 8 through 19 months at high risk and eligible for palivizumab (Synagis, AstraZeneca):

  • Children with chronic lung disease of prematurity who require medical support during the six months before the start of their second RSV season
  • Children who are severely immunocompromised
  • Children with evidence of severe cystic fibrosis (previous hospitalization for pulmonary exacerbation in the first year of life or abnormalities on chest imaging that persist when stable) or that have weight-for-length that is less than the 10th percentile

If nirsevimab is given to a child eligible for palivizumab, do not give palivizumab. If nirsevimab is unavailable, CDC recommends that palivizumab (a short-acting RSV monoclonal antibody) should be administered per AAP recommendations (see https://doi.org/10.1542/peds.2023-061803). Because palivizumab is effective for 30 days, if nirsevimab becomes available during the RSV season, do not administer nirsevimab within 30 days of a dose of palivizumab. Do not give palivizumab during the season after administering nirsevimab.

The full ACIP recommendation is available at www.cdc.gov/mmwr/volumes/72/wr/pdfs/mm7234a4-H.pdf.

Last reviewed: January 22, 2024

Yes. Evidence continues to demonstrate that COVID-19 vaccination is safe and effective during any stage of pregnancy; the benefits of vaccination clearly outweigh any known or potential risks of COVID-19 vaccination during pregnancy. The currently licensed or authorized COVID-19 vaccines are non-replicating vaccines and cannot cause infection in either the pregnant person or the fetus. No evidence exists of risk to the fetus from vaccinating pregnant people with non-replicating vaccines in general.

Data from the Vaccine Adverse Events Reporting System (VAERS), the V-safe surveillance system, and the V-safe pregnancy registry have not signaled any safety concerns for pregnant people who were vaccinated or their infants. The vaccine manufacturers are following the pregnancy outcomes of people in the clinical trials who became pregnant. Additional studies in pregnant people are ongoing in order to fully evaluate pregnancy and birth outcomes.

All people who are pregnant are recommended to receive an updated (2023–2024 Formula) COVID-19 vaccine, as licensed or authorized by FDA, if they have not already received one.

Last reviewed: March 19, 2024

Syncope (fainting) can occur before or after vaccination because of a vasovagal response to needles. Children should be seated or lying down during vaccination. Consider observing patients (with the patient seated or lying) for 15 minutes after vaccination to decrease the risk for injury should the patient faint. If syncope develops, the patient should be observed until the symptoms resolve.

Last reviewed: February 16, 2022

Tdap vaccination for adolescents is recommended at age 11–12 years. A 10-year-old who is already up to date on diphtheria/tetanus/pertussis vaccines and gets a Tdap vaccine for any reason does not need to receive another Tdap at age 11–12 years.

Last reviewed: March 31, 2022

Test pregnant people who lack either (1) documentation of receipt of 2 doses of varicella vaccine or (2) healthcare provider diagnosis or verification of varicella or herpes zoster disease. Those who are not immune should begin the 2-dose vaccination series immediately postpartum.

Last reviewed: May 16, 2023

No. A number of studies have shown that HCP are not at significantly increased risk of HAV infection because of their occupation. However, if HCPs are going to work (or vacation) in a country with a high or intermediate endemic rate of HAV infection, they are at risk of HAV infection and should be vaccinated. The only occupational indications for routine HepA vaccination are work with non-human primates or live HAV in a laboratory setting.

Last reviewed: June 25, 2023

Yes. This was a vaccine administration error since Twinrix, a combination hepatitis A/hepatitis B vaccine, is not licensed for people younger than 18. However, the hepatitis A and hepatitis B components can be counted as valid doses. The third dose of the Twinrix series should be given at least five months after the second dose.

Last reviewed: July 15, 2023

Antibody titers to vaccine-preventable diseases decline during the 1-4 years after HCT, if the recipient is not revaccinated. HCT recipients are at increased risk for certain vaccine-preventable diseases, including those caused by encapsulated bacteria. In short, all HCT recipients should begin revaccination with inactivated vaccines 6 months after HCT. Three doses of pneumococcal conjugate vaccine (PCV) should be given 6 months following transplant followed by a dose of pneumococcal polysaccharide vaccine (PPSV) at least 8 weeks later. HCT recipients should receive 3 doses of Hib vaccine starting 6 to 12 months after successful transplant, regardless of vaccination history; doses should be administered at least 4 weeks apart. Immunocompetent people should receive MMR vaccine 24 months after transplant. For a complete discussion of the indications and schedule of vaccination, refer to the sub-section on recipients of HCT in the Altered Immunocompetence section of ACIP’s “General Best Practices Guidelines for Immunization” available at www.cdc.gov/vaccines/hcp/acip-recs/general-recs/immunocompetence.html.

Last reviewed: August 29, 2022

There are insufficient data available to inform assessment of Heplisav-B or PreHevbrio vaccine-associated risks during pregnancy.

Dynavax has established a Heplisav-B Vaccination in Pregnancy Registry in order to understand the effect (if any) of Heplisav-B vaccination during pregnancy. Individuals who receive Heplisav-B within 28 days before pregnancy or at any time during pregnancy are encouraged to participate in the registry by calling 1-844-443-7734 (toll-free).

VBI has established a registry that monitors pregnancy outcomes in mothers exposed to PreHevbrio during pregnancy. Individuals who receive PreHevbrio during pregnancy are encouraged to contact 1-888-421-8808 (toll-free).

Last reviewed: July 21, 2023

No, do not restart the series. You should continue where the patient left off and complete the series.

Last reviewed: March 2, 2024

An adult who has documentation of one dose of varicella vaccine is potentially at risk for chickenpox (from exposure to a person with chickenpox) AND herpes zoster (either from a possible previous unrecognized case of chickenpox or from the vaccine strain of the virus).

CDC subject matter experts advise that clinical management of a person with no proof of a past primary varicella infection and a history of only one varicella vaccination who is or will be immunocompromised depends upon the degree of immunocompromise of the patient:

  • If varicella vaccine is not already contraindicated due to significant immunocompromise, give the second varicella vaccine dose. Depending on the patient’s immunocompromising condition or therapy, the clinician may then consider initiating the Shingrix series at least 8 weeks after the second varicella vaccine dose to reduce the risk of herpes zoster.
  • If the patient already has significant immunocompromise and the second varicella vaccine dose is contraindicated, the clinician should:
    • Consider the patient’s herpes zoster risk (based on their immunocompromising condition or therapy). On a case-by-case basis and if the clinician determines it is indicated, administer the Shingrix series to reduce the risk of herpes zoster.
    • Be prepared to administer varicella immune globulin (VariZIG, Saol Therapeutics) in the event that the patient has a recognized exposure to a person with chickenpox, regardless of whether or not the patient received RZV.

For more information, see www.cdc.gov/shingles/vaccination/immunocompromised-adults.html.

Last reviewed: March 9, 2022

Most empty vaccine vials are not considered hazardous or pharmaceutical waste and do not require disposal in a biomedical waste container. Check and comply with your state requirements for disposal. Medical waste disposal requirements may vary from state to state because they are set by state environmental agencies. Contact your immunization program or state environmental agency for guidance to ensure your facility’s vaccine disposal procedures comply with state and federal regulations.

An exception to this principle is that an empty rotavirus vaccine dispensing tube or oral applicator is considered medical waste and should be disposed of in a medical waste container.

Last reviewed: July 26, 2023

CDC publishes and routinely updates a comprehensive Vaccine Storage and Handling Toolkit covering topics such as vaccine storage units, temperature monitoring devices, and inventory management, vaccine transport and emergency vaccine storage and handling. The toolkit also contains troubleshooting guides to assist with vaccine storage unit issues or temperature excursions. This terrific resource, along with other vaccine storage and handling resources from CDC, is available online at www.cdc.gov/vaccines/hcp/admin/storage/toolkit/index.html.

In addition, Immunize.org maintains many free, downloadable materials at www.immunize.org/handouts/vaccine-storage-handling.asp.

Last reviewed: July 26, 2023

Yes. A dose administered up to 4 days before the minimum interval for that dose may be counted as valid and does not need to be repeated.

Last reviewed: March 2, 2024

Infants and children 8 months through 19 months of age who meet one or more of the criteria listed below are recommended to receive one dose of nirsevimab (200 mg, administered as two 100-mg MFS injections given at the same time at different injection sites) just before or during their second RSV season:

  • Children with chronic lung disease of prematurity who required medical support (chronic corticosteroid therapy, diuretic therapy, or supplemental oxygen) any time during the 6-month period before the start of the second RSV season
  • Children with severe immunocompromise
  • Children with cystic fibrosis who have either 1) manifestations of severe lung disease (previous hospitalization for pulmonary exacerbation in the first year of life or abnormalities on chest imaging that persist when stable), or 2) weight-for-length less than the 10th percentile
  • American Indian or Alaska Native (AI/AN) children

Nirsevimab is particularly important for AI/AN children who live in remote regions, where access to medical care may be challenging, or in areas where there are known high rates of severe disease among older infants and toddlers.

Last reviewed: January 22, 2024

Yes. Adalimumab is a potent anti-inflammatory drug that blocks the activity of tumor necrosis factor (TNF). Adalimumab is considered immunosuppressive because serious infections have been reported in people taking the drug, including tuberculosis and infections caused by viruses, fungi, or bacteria. A person taking adalimumab or other drugs that affect TNF activity (such as infliximab [Remicade], certolizumab pegol [Cimzia], golimumab [Simponi], or etanercept [Enbrel]) should be considered to have immunosuppression and receive either PCV20 alone or PCV15 followed by PPSV23. Clinicians can consider giving PPSV23 as soon as 8 weeks after PCV15 in this case, in order to accelerate protection against strains of pneumococcus unique to PPSV23.

Last reviewed: April 5, 2024

As with all vaccines, a severe allergic reaction (for example, anaphylaxis) to a vaccine component or to a prior dose is a contraindication to further doses of that vaccine. A moderate or severe acute illness is a precaution; vaccination should be deferred until the person’s condition has improved. Because MenB is an inactivated vaccine it can be administered to persons who are immunosuppressed as a result of disease or medications; however, response to the vaccine might be less than optimal. Data on MenB vaccination during pregnancy is limited. Pregnancy a precaution to MenB vaccination, but MenB may be administered if, in the judgment of the clinician, the benefits outweigh any potential risks.

Last reviewed: March 24, 2024

Yes. The current VIS for Dengvaxia is available in both English and Spanish at www.immunize.org/vis/vis_dengue.asp.

Last reviewed: February 16, 2022

Yes, you can. Many of the conditions previously considered to be precautions to DTaP (e.g., temperature of 105°F or higher, collapse or shock-like state, persistent crying lasting 3 hours or longer, seizure with or without fever) did not apply to Tdap. These conditions are also no longer considered to be precautions to DTaP. This issue is addressed in the current ACIP statement, available at www.cdc.gov/mmwr/volumes/67/rr/pdfs/rr6702a1-H.pdf, page 3.

Last reviewed: March 31, 2022

Commercially available laboratory tests for varicella antibody are usually based on a technique called EIA (enzyme immunoassay). Though these tests are sufficiently sensitive to detect antibody resulting from varicella zoster virus infection, they are generally not sensitive enough to detect vaccine-induced antibody. The more sensitive assays needed to detect vaccine-induced antibody are not widely available. This is why CDC does not recommend antibody testing after varicella vaccination.

Last reviewed: May 16, 2023

No. In the past, outbreaks of hepatitis A occurred among children in child care centers, infecting employees of those centers, especially those caring for infants and toddlers. Following widespread adoption of early childhood vaccination against hepatitis A, outbreaks in child care centers are now rare.

Last reviewed: June 25, 2023

For routine vaccination, children without contraindications to MMR vaccine should receive 2 doses of MMR vaccine with the first dose at age 12–15 months old and the second dose at age 4–6 years old. The minimum interval is 28 days for dose 2. If you have an outbreak in your community or a child is traveling internationally, then consider using the minimum interval instead of waiting until age 4–6 years old for dose 2.

Last reviewed: June 19, 2023

Yes. CDC advises that doses of FluMist administered in past seasons can be counted.

Last reviewed: September 10, 2023

It is prudent to allow the alcohol to evaporate, but it is unlikely that the small amount residual alcohol on the skin will affect the vaccine or increase the risk of an adverse reaction.

Last reviewed: December 28, 2022

Twinrix is normally given as a 3-dose series on a schedule of 0, 1, and 6 months. However, if someone needs protection sooner (e.g., imminent foreign travel), you can give it as a 4-dose series at intervals of 0, 7, and 21–30 days, followed by a fourth (booster) dose at least 12 months after the first dose.

Last reviewed: July 15, 2023

Children with SCID may be given inactivated vaccines (e.g., DTaP, Hib, hepatitis B, pneumococcal conjugate, hepatitis A, IPV, and injectable influenza). They should not be given live virus vaccines (e.g., live attenuated influenza, MMR, rotavirus, and varicella).

Last reviewed: August 29, 2022

Decreased seroconversion rates might occur among preterm infants with birth weights less than 2,000 grams after administration of HepB at birth. However, by the chronological age of 1 month, all preterm infants, regardless of initial birth weight, are likely to respond as adequately as larger infants. Infants who weigh less than 2,000 grams born to HBsAg-positive mothers and mothers with unknown HBsAg status (if the mother’s HBsAg status cannot be determined within 12 hours of birth) must receive immunoprophylaxis with HepB and hepatitis B immune globulin (HBIG) within 12 hours of birth. The initial vaccine dose should not be counted toward completion of the hepatitis B series, and 3 additional doses of HepB should be administered, beginning when the infant is age 1 month. Infants weighing less than 2,000 grams born to HBsAg-negative mothers should receive the first dose of the HepB series at hospital discharge or at chronological age 1 month (even if weight is still less than 2,000 grams), whichever comes first.

Last reviewed: July 21, 2023

Immunocompromised adults age 19 years and older without evidence of exposure to live varicella virus through a history of chickenpox, zoster, or documentation of vaccination with live varicella vaccine (Varivax or ProQuad, Merck) or zoster vaccine live (Zostavax, Merck) should be evaluated further for their risk of zoster before receiving Shingrix. Birth before 1980 is not sufficient proof of a history of primary varicella infection (chickenpox) for immunocompromised adults.

Vaccination with varicella vaccine to prevent chickenpox may be considered for a patient with well-controlled HIV (e.g., CD4+ T-lymphocyte percentage of at least 15% and a count of at least 200 cells per microliter) and no evidence of a history of varicella disease or vaccination. Vaccination may be considered for a patient who has a CD4 count of at least 200 cells per microliter but no information on percentage. Vaccination is contraindicated if a patient has laboratory information on the CD4 percentage and/or count and either measure falls below the recommended acceptable threshold for vaccination.

For other situations involving immunocompromised adults with no evidence of a history of varicella disease or vaccination, see detailed guidance provided by CDC at www.cdc.gov/shingles/vaccination/immunocompromised-adults.html#special-populations.

Last reviewed: March 9, 2022

The CDC Storage and Handling Toolkit, available at www.cdc.gov/vaccines/hcp/admin/storage/toolkit/storage-handling-toolkit.pdf, contains information about recommended features to look for when selecting a temperature monitoring device or storage unit. If you store Vaccines for Children (VFC) or other federally-purchased vaccines, you may contact your state immunization manager or Vaccines for Children (VFC) coordinator for additional information on their recommendations or requirements. Contact information can be found here: www.immunize.org/coordinators.

Another option is to look for units that have the NSF/ANSI 456 certification. A refrigerator or freezer that is NSF-certified for vaccine storage means the units have been tested and certified to meet the NSF/American National Standards Institute (ANSI) 456 standards for construction and performance of vaccine refrigerators and freezers used in healthcare settings where vaccines are given. These standards were developed through a collaboration with NSF, CDC, healthcare providers, public health agencies, equipment manufacturers, and vaccine manufacturers, including experts from Immunize.org.

CDC does not require NSF-certified units for vaccine storage in the Vaccines for Children program or any other federal program. Not all storage units capable of reliably storing vaccines have this certification; however, all storage unit models with this certification have met design and performance standards to properly store vaccines under a range of normal clinic conditions.

Last reviewed: July 26, 2023

The optimal timing for nirsevimab to be administered is shortly before the RSV season begins; however, nirsevimab may be administered to eligible infants and children who have not yet received a dose at any time during the season.

Nirsevimab should be administered to infants less than 8 months old and infants and children 8 through 19 months old during the months of October through March in most areas in the United States, unless otherwise advised by public health authorities. Adjustment of timing due to RSV activity outside this typical timeframe is most likely to be necessary in more tropical climates and in Alaska.

Last reviewed: January 22, 2024

Yes. COVID-19 vaccination is recommended for all people who are not up to date, including those who are pregnant or lactating. Pregnant people are at increased risk of severe complications and death from COVID-19 compared to non-pregnant people of the same age. Those who contract COVID-19 during pregnancy also have almost twice the risk of stillbirth compared to those who do not contract COVID-19 during pregnancy. Studies have shown that antibodies produced after COVID-19 vaccination during pregnancy are transferred to the newborn, and COVID-19 vaccination of people who are pregnant reduces the risk of COVID-19 hospitalization in infants younger than 6 months. Pregnant people should receive any licensed or authorized updated 2023–2024 Formula COVID-19 vaccine during pregnancy, as licensed or authorized by FDA.

There is no recommendation from CDC for COVID-19 vaccination during every pregnancy; therefore, at this time, a person who is up to date on COVID-19 vaccination and becomes pregnant is not recommended to get an additional dose.

CDC, the American College of Obstetricians and Gynecologists (ACOG), and the Society for Maternal-Fetal Medicine (SMFM) all recommend vaccination, when indicated, of pregnant people at any stage of pregnancy.

For more details about COVID-19 vaccination during pregnancy, visit CDC’s webpage, “COVID-19 Vaccines while Pregnant or Breastfeeding”: www.cdc.gov/coronavirus/2019-ncov/vaccines/recommendations/pregnancy.html.

Last reviewed: March 19, 2024

Few data are available on the effect of MenB vaccines on pregnancy. The manufacturers do not consider pregnancy to be a contraindication to use of MenB. GSK has established a Vaccination in Pregnancy registry. People who receive Bexsero during pregnancy may access information about the GSK Bexsero Pregnancy Registry here: https://pregnancyregistry.gsk.com/bexsero.html. Pfizer also maintains a Vaccination in Pregnancy registry for Trumenba, although specific contact details for this registry are not available. In general, vaccination against MenB should be deferred during pregnancy; however, MenB may be administered if, in the judgment of the clinician, the benefits outweigh any potential risk.

Last reviewed: March 24, 2024

Yes. If an HPV vaccine dose is administered at less than the recommended minimum interval, then the dose should be repeated. The repeat third dose should be repeated 5 months after the first dose or 12 weeks after the invalid third dose, whichever is later.

Last reviewed: March 2, 2024

No, Dengvaxia is not included in the VICP at this time.

For additional information, visit www.hrsa.gov/vaccine-compensation/faq.

Last reviewed: February 16, 2022

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