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 (1372)

No. The vaccine series need not be restarted if more than 6 months have elapsed since the first dose.

Last reviewed: March 9, 2022

For most people who need only 1 dose of influenza vaccine, vaccination should ideally be offered in September and October. For people not vaccinated by the end of October, vaccination efforts should continue as long as influenza viruses are circulating and unexpired vaccine is available.

Vaccination in July and August should be avoided for most groups unless there is concern that vaccination later in the season might not be possible. Early vaccination has been associated with waning of vaccine-induced immunity and decreased vaccine effectiveness before the end of the influenza season, particularly among older adults.

Vaccination in July and August may be considered for people in their third trimester of pregnancy, to allow time for protective maternal antibodies to transfer to the fetus, providing protection during early infancy. Children younger than age 9 years who need two doses of vaccine this season should receive their first dose as soon as possible so that they can get their second dose before the end of October. Children who need only one dose can be considered for vaccination in July or August.

Last reviewed: August 11, 2024

As of January 2020, ACIP recommends that Td or Tdap may be administered in any situation when only Td vaccine was previously recommended. Someone who received a dose of Tdap at age 11 or 12 years should receive a booster dose of Td or Tdap vaccine ten years later, unless tetanus prophylaxis is required sooner due to an injury or if Tdap vaccination is needed during pregnancy.

Last reviewed: March 31, 2022

Try to follow general guidelines for oral administration of liquid vaccines. First, give this vaccine at the beginning of the office visit, while the baby is still happy, and before you administer injections or perform other procedures. Second, make every effort to aim the dropper containing the vaccine down one side and toward the back of the child’s mouth. Don’t put the dropper so far back that you gag the child. You may find the following information from the RotaTeq manufacturer helpful: www.merckvaccines.com/Products/RotaTeq/Pages/dosageandadministration. You can also find a pictorial description of both reconstitution and administration of the lyophilized formulation of Rotarix at www.rotarixhcp.com/dosage/administration/.

Last reviewed: June 7, 2023

Immunize.org has prepared a document that provides a summary of the ACIP recommendations for use of MenACWY for people of all ages. The document is available at www.immunize.org/catg.d/p2018.pdf.

Last reviewed: November 15, 2024

No. There is no screening laboratory test that can determine whether a person is already immune or still susceptible to any given HPV type. Most sexually active adults have been exposed to one or more HPV types, although not necessarily all of the HPV types targeted by vaccination. HPV vaccine works to prevent infection with vaccine types to which a person is still susceptible.

Last reviewed: March 2, 2024

People who do not have a functioning spleen or who have had a splenectomy are at increased risk for infection with encapsulated bacteria, especially Pneumococcus, Neisseria meningitidis, and Haemophilus influenzae type b (Hib).

In addition to receiving routine vaccinations, children and adults without a functioning spleen who are age 2 years and older need additional pneumococcal vaccinations, with specific recommendations dependent on an individual’s age and specific pneumococcal vaccination history. Refer to current immunization schedules, Immunize.org’s standing orders templates for pneumococcal vaccination, or CDC’s PneumoRecs VaxAdvisor Mobile App.

All asplenic people should receive a primary series of at least 2 doses of meningococcal ACWY vaccine (MenACWY) with a booster dose every 5 years. See the MenACWY recommendation table at www.immunize.org/catg.d/p2018.pdf for details. Asplenic people age 10 years and older should also receive a series (either 2 or 3 doses depending on the vaccine brand) of meningococcal serogroup B vaccine (MenB) with an initial booster dose one year after completion of the primary series and subsequent booster doses every 2–3 years thereafter. A pentavalent MenABCWY vaccine (Penbraya, Pfizer) is also an option in certain circumstances.

Two doses of Hib vaccine should be given to unimmunized children 12–59 months of age (defined as a child who received zero or 1 dose before 12 months of age). A single dose of Hib vaccine should be administered to unimmunized people age 5 years or older (defined as those who have not received at least 1 dose of Hib vaccine after 14 months of age).

Last reviewed: April 10, 2024

In 2023, when RSV vaccines were initially licensed, ACIP recommended use of RSV vaccine for anyone 60 years and older based on shared clinical decision-making, which includes a conversation about individual risks and benefits of vaccination with a healthcare provider. The recommendation was made when there were limited data about how well the vaccine would work in preventing RSV-associated hospitalization or death due to the relatively healthy older adults enrolled in the clinical trials. There was also a question about whether (or how frequently) a person would need revaccination and whether the vaccination might increase the rare risk of Guillain-Barré syndrome. Given these uncertainties, ACIP members felt that people should have the option to choose to receive RSV vaccine or wait until their risk of serious RSV disease escalates, as it does after age 75. Shared clinical decision-making proved time-consuming and difficult to implement for healthcare providers and patients, due to the lack of clarity about who should prioritize RSV vaccination.

Updated evidence on the balance of RSV vaccination benefits and risks led ACIP in June 2024 to make a definitive routine age-based recommendation for adults age 75 years and older, accompanied by a risk-based recommendation for those age 60 through 74 years with specific high-risk conditions. Due to the relatively small benefit of vaccination for healthy people younger than age 75 and the ongoing uncertainty about revaccination, the option for vaccination of people age 60 through 74 years without risk factors for severe RSV disease was removed.

Last reviewed: August 25, 2024

All infants should be given a primary series of either PCV15 or PCV20, at ages 2, 4, and 6 months with a booster at age 12 to 15 months. Otherwise healthy children who fall behind should be given catch-up vaccination through age 59 months; if they have certain underlying medical conditions they should be given catch-up vaccination through age 71 months.

For pneumococcal vaccination of children ages 2 through 5 years, see the job aid linked to the CDC summary of recommendations here: www.cdc.gov/pneumococcal/hcp/vaccine-recommendations/index.html.

Immunize.org offers a print-ready clinical resource that addresses pneumococcal vaccination recommendations for all children, including those with any relevant health condition or incomplete vaccination history, entitled Recommendations for Pneumococcal Vaccines Use in Children and Teens: www.immunize.org/wp-content/uploads/catg.d/p2016.pdf.

Last reviewed: November 13, 2024

As of August 2024, both MenB vaccine products, Bexsero (MenB-4C, GSK) and Trumenba (MenB-FHbp, Pfizer) require a minimum of 6 months to complete the MenB vaccination series. There is no way for this student to complete the vaccine series sooner. The student will need to follow up with the university about its policy in this situation.

If accelerated protection is desired for a person who is not at high risk of MenB disease, as in this situation, it is permissible to use the 3-dose MenB schedule (0, 1-2 months, 6 months) so that the student may receive 2 of 3 doses before leaving for college. He would still need a third dose of MenB vaccine (same brand as the first two doses) at least 6 months after dose 1 and at least 4 months after dose 2 to complete the series.

Last reviewed: November 15, 2024

For the general public, only one HepB series is routinely recommended in a lifetime, with specific exceptions described below.

As of April 2022, CDC recommends HepB vaccination of the following:

  • Routine HepB vaccination of all infants, beginning with a birth dose.
  • Routine HepB vaccination of all children and adults through age 59 years.
  • Vaccination of all adults age 60 years and older with risk factors for hepatitis B:
    • People at risk for infection by sexual exposure
      • Sex partners of people testing positive for HBsAg
      • Sexually active people who are not in a long-term, mutually monogamous relationship (e.g., those with more than one sex partner during the previous 6 months)
      • People seeking evaluation or treatment for a sexually transmitted infection
      • Men who have sex with men
    • People at risk for infection by percutaneous or mucosal exposure to blood
      • People with current or recent injection drug use
      • Household contacts of people testing positive for HBsAg
      • Residents and staff members of facilities for people with developmental disabilities
      • Health care and public safety personnel with reasonably anticipated risk for exposure to blood or blood-contaminated body fluids
      • People on maintenance dialysis, including in-center or home hemodialysis and peritoneal dialysis, and people who are predialysis
      • People with diabetes, at the discretion of the treating clinician
    • Others
      • International travelers to countries with high or intermediate levels of endemic HBV infection (HBsAg prevalence of 2% or higher)
      • People with hepatitis C virus infection
      • People with chronic liver disease (including, but not limited to, people with cirrhosis, fatty liver disease, alcoholic liver disease, autoimmune hepatitis, and an alanine aminotransferase or aspartate aminotransferase level greater than twice the upper limit of normal)
      • People with HIV infection
      • People who are incarcerated
  • Adults age 60 or older years without known risk factors for hepatitis B infection may be offered and receive HepB.

People with documentation of complete vaccination or documentation of previous HBV infection generally do not need to be vaccinated; however, there is no evidence that administration of additional doses of HepB to someone who is already immune or infected is harmful. Serologic testing is not required before vaccination and should not pose a barrier to access to vaccination. If testing is done, it may be done at the same visit when the first dose of vaccine is administered.

Revaccination is recommended only for individuals for whom post-vaccination serologic testing (PVST) is recommended and evidence of nonresponse is found. Annual serologic testing of people undergoing dialysis is recommended, with booster doses administered when detectable antibodies drop below 10 mIU/mL. Annual testing and revaccination may be indicated for other immunocompromised people. See CDC 2018 ACIP recommendations for a detailed discussion of these issues: www.cdc.gov/mmwr/volumes/67/rr/pdfs/rr6701-H.pdf (pages 21-24).

Last reviewed: January 17, 2025


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Last reviewed: August 11, 2024


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Last reviewed: June 7, 2024

No. CDC recommends that every vaccine storage unit must have its own TMD. An accurate temperature history that reflects actual vaccine temperatures is critical for protecting your vaccines. It is also recommended to have at least one backup TMD on site in case a primary device breaks or malfunctions.

Last reviewed: July 26, 2023

It is critical to vaccinate susceptible older children and adults whenever the opportunity arises. With younger children being routinely vaccinated, the chance of being exposed to cases of chickenpox is decreasing. Older children, adolescents, and adults who have not had chickenpox now have a greater chance of remaining susceptible. These older individuals, when they contract chickenpox, are more likely to become seriously ill and have disease complications than younger children.

Last reviewed: May 16, 2023

Depending on conditions, HAV can be stable in the environment for months; freezing does not inactivate (i.e., render non-infectious) HAV. HAV is inactivated by heating foods to temperatures greater than 185°F (85°C) for 1 minute. In addition, HAV on surfaces is inactivated by disinfecting surfaces with a 1:100 dilution of sodium hypochlorite (i.e., household bleach) in tap water.

Adequately chlorinating water through water treatment processes and dilution in public water systems kills HAV. Spas and swimming pools that are adequately treated are not likely to pose a risk for HAV outbreaks.

Last reviewed: June 25, 2023

Influenza vaccine and Td (or Tdap) may be given at the same time or at any time before or after a dose of pneumococcal polysaccharide vaccine. The only time you have to wait is when two LIVE vaccines are not given at the same visit; then you need to wait at least 4 weeks to give the second live vaccine.

Last reviewed: June 6, 2023

The National Vaccine Injury Compensation Program (NVICP) includes payment only for injuries determined to have occurred following vaccination with a vaccine routinely recommended for children or pregnant women in the United States. The recipient can be of any age, but the vaccine must be routinely recommended for children through age 18 years or pregnant women. The vaccine must be subject to an excise tax to be included in the program. Shingrix and PPSV23 vaccines are not routinely recommended for children or pregnant women; Shingrix is only recommended for adults. COVID-19 vaccines will transition from injury compensation coverage under the Countermeasure Injury Compensation Program to NVICP once criteria are met for inclusion in NVICP. More information about the program and the covered vaccines is at www.hrsa.gov/vaccine-compensation/covered-vaccines/index.html.

Last reviewed: August 31, 2022

Instructions on the use of VISs and many additional items are available on the CDC website at www.cdc.gov/vaccines/hcp/vis/index.html or from your state immunization program. You can also visit Immunize.org’s website at www.immunize.org/vis for links to many important documents about the use of VISs.

Last reviewed: June 6, 2023

It may take 2 to 7 days to stabilize the temperature in a newly installed or repaired refrigerator or 2 to 3 days for a freezer. Before using a unit for vaccine storage, check and record the minimum and maximum temperatures each workday for two to seven days. If temperatures cannot be recorded using a continuous digital data logger, check and record temperatures a minimum of two times each workday. Once you have two consecutive days of temperatures recorded within the recommended range, your unit is stable and ready for use. Recommended temperatures are between 2°C and 8°C (36°F and 46°F) for the refrigerator and between -50°C and -15°C (-58°F and +5°F) for the freezer.

Last reviewed: July 26, 2023

The manufacturer has not addressed this issue but CDC considers administration of rotavirus vaccine via gastrostomy tube to be acceptable practice. There should be no problem flushing the tube after vaccine has been administered.

Last reviewed: June 7, 2023

Hib vaccine is not routinely recommended for healthy adults 19 years and older, even if the person did not receive Hib vaccine as a child. However, ACIP recommends that one dose of Hib vaccine should be administered to persons who have anatomical or functional asplenia or sickle cell disease or are undergoing elective splenectomy if they have not previously received Hib vaccine. Hib vaccine should be administered 14 or more days before splenectomy if possible. Recipients of a hematopoietic stem cell transplant should be vaccinated with a 3-dose series of Hib vaccine 6 to 12 months after a successful transplant, regardless of vaccination history; at least 4 weeks should separate doses. Hib vaccine is not recommended for adults with HIV infection since their risk for Hib disease is low.

Last reviewed: July 31, 2022

Dengvaxia is a live-attenuated vaccine and 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 below 200 per cubic milliliter.

The ACIP recommendations state that Dengvaxia may be used with precaution in people with HIV infection who do not meet the criteria for contraindication, based on an assessment of the person’s risk of vaccination against the risk of dengue and its complications.

Last reviewed: January 17, 2025

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 time frame as to what “immediately” means. CDC recommends that the provider contact the manufacturer any time (s)he has any question about whether or not the vaccine has been used in the appropriate time frame.

Last reviewed: December 28, 2022

No. Adults with evidence of immunity do not need any further vaccines. No “booster” doses of MMR vaccine are recommended for either adults or children. They are considered to have life-long immunity once they have received the recommended number of MMR vaccine doses or have other evidence of immunity.

Last reviewed: June 19, 2023

Complete the series based on shared clinical decision-making involving the patient’s risk and desire for protection.

Last reviewed: March 2, 2024

No.

Last reviewed: March 9, 2022

CDC and ACIP make no recommendation for revaccination later in the season of people who have been fully vaccinated for the season, regardless of when the current season vaccine was received.

Last reviewed: August 11, 2024

Yes. CDC recommends that whenever feasible, only one manufacturer’s DTaP product be used for the entire pertussis series, but that vaccinations should not be deferred if the DTaP product previously given is unavailable or unknown.

Last reviewed: July 15, 2023

A pregnant person may administer any vaccine except live, replication-competent smallpox vaccine (ACAM2000, Emergent Biosolutions).

Last reviewed: August 29, 2022

Yes. Sometimes ACIP makes recommendations that differ from the FDA-approved package insert indications, and this is one of those instances. ACIP recommendations represent the standard of care for vaccination practice in the United States.

Last reviewed: March 31, 2022

The conditions that increase the risk of pneumococcal disease and are indications for additional pneumococcal vaccine doses beyond the routine schedule are broken down into two categories: non-immunocompromising (non-IC) and immunocompromising (IC). Recommendations differ slightly under certain circumstances by IC or non-IC category.

Non-IC conditions include:

  • Cerebrospinal fluid (CSF) leak
  • Chronic heart disease (especially cyanotic congenital heart disease and heart failure)
  • Chronic kidney disease (except as specified in the IC list below)
  • Chronic liver disease
  • Chronic lung disease (including moderate persistent or severe persistent asthma)
  • Diabetes mellitus
  • Cochlear implant

Immunocompromising (IC) conditions include:

  • Kidney disease and on maintenance dialysis
  • Kidney disease with nephrotic syndrome
  • Asplenia or splenic dysfunction
  • Congenital or acquired immunodeficiency, including B-(humoral) or T-lymphocyte deficiency; complement deficiencies, particularly C1, C2, C3, and C4 deficiency; and phagocytic disorders (excluding chronic granulomatous disease)
  • Treatment with immunosuppressive drugs or radiation therapy (including treatment for Hodgkin disease, leukemias, lymphomas, malignant neoplasm, and solid organ transplant)
  • HIV infection
  • Sickle cell disease or other hemoglobinopathies

An older child through age 18 years with any high-risk condition who completed a pneumococcal conjugate series before age 6 years that included any dose of PCV20, is not recommended to receive any additional PCV doses.

Children with IC or non-IC conditions who completed a PCV series before age 6 years with PCV13 or PCV15 (but who have not received PCV20 or pneumococcal polysaccharide vaccine [PPSV23]) should receive additional pneumococcal vaccination with a single dose of PCV20 at least 8 weeks after the most recent PCV dose. If PCV20 is not available, a non-IC or IC child in this circumstance may, alternatively, receive a single dose of PPSV23 at least 8 weeks after the most recent PCV dose. An IC child given PPSV23 in this circumstance would also be due for a dose of either PCV20 or a second dose of PPSV23 at least 5 years after the first PPSV23.

Doses of the 7-valent PCV (the original Prevnar, PCV7) do not count toward PCV vaccination when determining the current pneumococcal vaccination needs of a child or teen with a qualifying non-IC or IC condition.

When feasible, administer any needed pneumococcal vaccination at least two weeks before initiating planned interventions that place a child at high risk (such as a cochlear implant or spleen removal).

Immunize.org details all recommendations and options for children with high-risk conditions in its standing order template for pneumococcal vaccination of children and teens (www.immunize.org/wp-content/uploads/catg.d/p3086.pdf) and its shorter resource, Recommendations for Pneumococcal Vaccines use in Children and Teens (www.immunize.org/wp-content/uploads/catg.d/p2016.pdf).

For a complete explanation of pneumococcal vaccination recommendations for ages 6 through 18 years, CDC has summarized the recommendations here: www.cdc.gov/vaccines/vpd/pneumo/hcp/who-when-to-vaccinate.html#children-6-18.

Last reviewed: November 13, 2024

Menveo, in the two-vial presentation that requires reconstitution, is approved for people age 2 months through 55 years. The one-vial formulation that does not require reconstitution was licensed in 2022 for ages 10 through 55 years and should not be used for children younger than age 10. For children beginning the vaccination series at age 2 months the schedule is 4 doses at age 2, 4, 6, and 12 to 15 months. Fewer doses are recommended for children beginning the vaccination series at age 7 months or older. See the Immunize.org document at www.immunize.org/catg.d/p2018.pdf for details.

ACIP recommends the use of Menveo in high-risk children 2 through 23 months of age: children with persistent complement deficiency, including those taking a complement inhibitor such as eculizumab (Soliris) or ravulizumab (Ultomiris), functional or anatomic asplenia, HIV infection, who travel to or reside in regions where meningitis is epidemic or hyperendemic, or who are at risk during a community outbreak attributable to a vaccine serogroup. MenQuadfi (MenACWY-TT) may be used for children at increased risk who are age 2 years and older. These recommendations are summarized in Table 3 of the recommendations published by ACIP in MMWR in 2020: www.cdc.gov/mmwr/volumes/69/rr/pdfs/rr6909a1-H.pdf.

Last reviewed: November 15, 2024

As long as he remains healthy, let him know that he can wait until age 75 to get an RSV vaccine. Plan to reassess his need for RSV vaccination periodically. If he develop a high-risk condition that puts him at increased risk of severe RSV disease before turning 75, you should vaccinate him at that point.

Last reviewed: August 25, 2024

Both the Pfizer-BioNTech COVID-19 Vaccine and the Moderna COVID-19 Vaccine are lipid nanoparticle-formulated, nucleoside-modified mRNA vaccines encoding the prefusion spike glycoprotein of SARS-CoV-2, the virus that causes COVID-19. The 2024–2025 formula targets the Omicron variant KP.2 sublineage of the spike protein.  Visit this CDC website for more details about how mRNA vaccines work: www.cdc.gov/covid/vaccines/how-they-work.html.

Last reviewed: November 16, 2024

The patient can complete the series with either vaccine. If the patient lacks a high-risk condition for meningococcal B disease and is not at high risk of exposure due to an ongoing outbreak, then simply administer the final dose in the 2-dose series 6 months after the initial dose of the selected product. There needs to be a 6-month interval between two doses of the same brand to complete a MenB series for a person who is not at increased risk.

If the person is at increased risk for meningococcal B disease and needs a 3-dose MenB series, then decide which product (Bexsero or Trumenba) you will use to complete dose 2 and dose 3 of the series. The second dose of the selected brand may be given no sooner than 4 weeks after the previous dose of the same brand AND at least 4 weeks after the last dose of the other brand. Dose 3 should be given no sooner than 6 months after dose 1 of the same brand and 4 months after dose 2 of the same brand.

Last reviewed: November 15, 2024

All current and recent past ACIP recommendations concerning hepatitis B vaccination are available at: www.cdc.gov/acip-recs/hcp/vaccine-specific/hepatitis-b.html.

The most recent recommendations for adult HepB vaccination were published in MMWR on April 1, 2022. This publication details the routine catch-up recommendation for HepB vaccination of all adults age 19 through 59 years. The document is available at www.cdc.gov/mmwr/volumes/71/wr/pdfs/mm7113a1-H.pdf.

The 2018 comprehensive ACIP HepB recommendations publication contains detailed guidance on pediatric vaccination, post-vaccination serologic testing of healthcare professionals and other select high risk individuals, as well as the prevention of mother-to-child transmission of hepatitis B. It is available at www.cdc.gov/mmwr/volumes/67/rr/pdfs/rr6701-H.pdf.

In addition to the published recommendations, CDC has summarized its information on hepatitis B and hepatitis B vaccination for healthcare professionals here: www.cdc.gov/vaccines/vpd/hepb/hcp/index.html.

Last reviewed: January 17, 2025

No. Shingles is caused by varicella zoster virus, the same virus that causes chickenpox. A history of shingles based on a healthcare provider diagnosis is evidence of immunity to chickenpox. A person who has had shingles does not need to be vaccinated against varicella. The person should still receive zoster vaccine, however, if it is not contraindicated and the person is age 50 or older or is age 19 or older and immunocompromised.

Last reviewed: May 16, 2023

Both killed and live attenuated measles vaccines became available in 1963. Live attenuated vaccine was used more often than killed vaccine. The killed vaccine was found to be not effective and people who received it should be revaccinated with live vaccine. Without a written record, it is not possible to know what type of vaccine an individual may have received. So, people born during or after 1957 who received killed measles vaccine or measles vaccine of unknown type, or who cannot document having been vaccinated or having laboratory-confirmed measles disease should receive at least 1 dose of MMR. Some people at increased risk of exposure to measles (such as healthcare professionals and international travelers) should receive 2 doses of MMR separated by at least 4 weeks.

Last reviewed: June 19, 2023

No, there is no chronic (long-term) infection. Even the small proportion of people who develop relapsing HAV recover after about 6 months. Once you have had HAV infection and recovered, you cannot get it again.

Last reviewed: June 25, 2023

LAIV can be administered at any time before or after receipt of a blood product. See www.cdc.gov/vaccines/hcp/acip-recs/general-recs/timing.html#, Table 3-5, footnote B.

Last reviewed: June 6, 2023

In a situation where the person’s vaccination status is not aligned with current recommendations at the time of exposure, the person should receive the same postexposure prophylaxis (PEP) regimen as an unvaccinated person. This includes human rabies immune globulin (HRIG) and 4 doses of vaccine (days 0, 3, 7 and 14).

For details on this and other scenarios related to sustaining long term immunogenicity in recipients of the 2-dose rabies primary series, please refer to the figure on page 624 of the May 6, 2022, MMWR at www.cdc.gov/mmwr/volumes/71/wr/pdfs/mm7118a2-H.pdf.

Last reviewed: May 14, 2023

An interim VIS can sometimes be released soon after licensure of the vaccine or after the official vote by ACIP is taken. The interim VIS is not replaced with a final version until the ACIP recommendations have been published and the new VIS has been developed according to legally-mandated procedures.

Last reviewed: June 6, 2023

The meningococcal ACIP recommendations don’t clearly state a minimum interval for MenACWY in this situation. However, the minimum interval for a pediatric MenACWY schedule would presumably be 4 weeks like for other pediatric vaccines on a 2-4-6 schedule. You should try to give a third dose before travel begins.

Last reviewed: November 15, 2024

Check and record storage unit minimum and maximum temperatures for the time since last measurement at the start of each workday. This is a requirement for VFC providers. The minimum and maximum temperatures recorded should be those obtained since the last workday when the minimum and maximum temperatures were reset. If your device does not display minimum and maximum temperatures, then check and record the current temperature a minimum of 2 times (at the start and the end of the workday). This should be done even if there is a temperature alarm at some point during the day.

Last reviewed: July 26, 2023

Yes. The effectiveness concerns with antibody-containing blood products (ACBP) do not apply to rotavirus vaccine, since it is administered orally and replication of the vaccine virus occurs in the GI tract, “separate” from the site of the ACBP. Note that the child should be carefully screened for other potential contraindications or precautions to vaccination since administration of immune globulin could indicate immunosuppression.

Last reviewed: June 7, 2023

When elective splenectomy is planned, vaccination with pneumococcal, meningococcal, and Hib vaccines should precede surgery by at least 2 weeks, if possible. If vaccines are not administered before surgery, they should be administered as soon as the person’s condition stabilizes after surgery.

Last reviewed: July 31, 2022

In general, no. According to ACIP’s “General Best Practice Guidelines for Immunization”, concerns about spacing between doses of live vaccines not given at the same visit applies only to live injectable or intranasal vaccines. So live oral cholera vaccine may be administered simultaneously or at any interval before or after administration of most other vaccines. One exception is Ty21a oral typhoid vaccine (Vivotif, Emergent Travel Health) and oral cholera vaccine. Oral cholera vaccine should be administered before Ty21a vaccine, and at least 8 hours should separate the cholera vaccine and the first dose of Ty21a.

Last reviewed: December 28, 2022

The action taken depends on why varicella vaccine was given in the first place. If it was given because the person tested negative for varicella antibody, then the next dose should be varicella vaccine. If the varicella vaccine was given in error (i.e., without serologic testing), then Shingrix should be given.

Last reviewed: March 9, 2022

Peak influenza activity generally occurs in the Northern Hemisphere during December through March, most frequently in January or February. Providers should continue vaccinating patients through spring, as long as there is continued circulation of influenza viruses and they have unexpired vaccine in stock and unvaccinated patients in their office.

Because influenza occurs in many areas of the world during April through September, vaccine should be given to travelers who missed vaccination in the preceding fall and winter. Another late season use of vaccine is for children younger than age 9 years who needed 2 doses of vaccine but failed to get their second dose. For each of these situations, vaccine can be given through the month of June since most injectable influenza vaccine has a June 30 expiration date.

Last reviewed: August 11, 2024

It is estimated that for every million doses administered, about one (~0.0001%) will result in an anaphylactic reaction following vaccination. The estimate for mRNA COVID-19 vaccines is slightly higher, at 2 to 5 anaphylactic reactions per million vaccinations given. With proper screening, most providers who administer thousands of vaccines in their lifetimes will never see an anaphylactic reaction.

Last reviewed: August 29, 2022

A history of tetanus disease is not a reason to avoid tetanus-containing vaccines. Tetanus disease does not produce immunity because of the very small amount of toxin required to produce illness. As long as your patient has no other contraindications, she should receive Tdap now. If she has no documentation of prior tetanus vaccination, she should receive a complete 3-dose primary series (dose #1 of Tdap, followed by dose #2 of Td or Tdap 4–8 weeks later, and dose #3 of Td or Tdap 6–12 months after dose #2).

Last reviewed: March 31, 2022

Immunize.org has prepared a document that provides a summary of the ACIP recommendations for use of MenB. The document is available at www.immunize.org/catg.d/p2035.pdf.

Last reviewed: November 15, 2024

Yes. In 2009 ACIP updated its recommendations for use of IPV, partly in response to the availability of newer combination vaccines (e.g., Pentacel) that include an IPV component. The change did not apply to children who had already completed an acceptable 4-dose series of IPV before the updated schedule was published in August 2009. Since August 2009, ACIP has recommended that children receive at least 1 dose of IPV at age 4 through 6 years, even if they have previously received 4 doses. The interval between the next-to-last and last dose should be at least 6 months. This updated recommendation applies to all IPV-containing vaccines, including combination vaccines as well as IPV given as a single product. This means that some children may receive a total of 5 doses, a practice ACIP considers acceptable. This is similar to the recommendation for the last dose in the DTaP series. To view the current polio vaccine recommendations, go to the ACIP recommendations website at www.cdc.gov/vaccines/hcp/acip-recs/vacc-specific/polio.html.

Last reviewed: July 15, 2023

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 all 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). The second dose should be given 1 to 2 months after the first dose, and the third dose should be given 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 dose is 5 calendar months.

If the vaccination series is interrupted, the series does not need to be restarted.

Last reviewed: March 2, 2024

Regardless of risk, all children should receive routine vaccination with either PCV15 or PCV20 as age-appropriate. A child age 2 through 18 years with any of the conditions listed below may require additional pneumococcal vaccination depending on their age and prior vaccination status.

The conditions that increase the risk of pneumococcal disease and are indications for additional pneumococcal vaccine doses beyond the routine schedule are broken down into two categories: non-immunocompromising (non-IC) and immunocompromising (IC). Recommendations differ slightly under certain circumstances by IC or non-IC category.

Non-IC conditions include:

  • Cerebrospinal fluid (CSF) leak
  • Chronic heart disease (especially cyanotic congenital heart disease and heart failure)
  • Chronic kidney disease (except as specified in the IC list below)
  • Chronic liver disease
  • Chronic lung disease (including moderate persistent or severe persistent asthma)
  • Diabetes mellitus
  • Cochlear implant

Immunocompromising (IC) conditions include:

  • Kidney disease and on maintenance dialysis
  • Kidney disease with nephrotic syndrome
  • Asplenia or splenic dysfunction
  • Congenital or acquired immunodeficiency, including B-(humoral) or T-lymphocyte deficiency; complement deficiencies, particularly C1, C2, C3, and C4 deficiency; and phagocytic disorders (excluding chronic granulomatous disease)
  • Treatment with immunosuppressive drugs or radiation therapy (including treatment for Hodgkin disease, leukemias, lymphomas, malignant neoplasm, and solid organ transplant)
  • HIV infection
  • Sickle cell disease or other hemoglobinopathies

For timing of vaccination following hematopoietic stem cell transplant, see see www.cdc.gov/vaccines/hcp/imz-best-practices/altered-immunocompetence.html

CDC guidance is available at www.cdc.gov/vaccines/vpd/pneumo/hcp/who-when-to-vaccinate.html.

Immunize.org details all recommendations and options for children with high-risk conditions in its standing order template for pneumococcal vaccination of children and teens (www.immunize.org/wp-content/uploads/catg.d/p3086.pdf) and its shorter resource, Recommendations for Pneumococcal Vaccines use in Children and Teens (www.immunize.org/wp-content/uploads/catg.d/p2016.pdf).

Last reviewed: November 13, 2024

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: January 17, 2025

No. Only a single dose of RSV vaccine is currently approved and recommended. There is no evidence at this time to determine if or when revaccination would be of value. Available evidence from clinical trials indicate that RSV vaccination provides meaningful protection against severe RSV disease for at least 2 RSV seasons.

People who were vaccinated for RSV during a previous pregnancy and are pregnant again should not receive RSV vaccination for prevention of RSV in their infant. Instead, the infant should receive nirsevimab (Beyfortus, Sanofi) after birth.

As more data become available, FDA and the ACIP will evaluate the benefit and timing of RSV revaccination and issue updated recommendations as needed.

Last reviewed: August 25, 2024

Pneumococcal conjugate vaccine (PCV), Haemophilus influenzae type b (Hib) vaccine, MenACWY, and meningococcal B vaccine should be given at least 14 days before a scheduled splenectomy, if possible. This is done so the patient is protected from these diseases before the spleen is removed; however, doses given during the 14 days before surgery also can be counted as valid. If the doses cannot be given prior to the splenectomy, they should be given as soon as the patient’s condition has stabilized after surgery. If PCV20 or PCV21 is given, pneumococcal polysaccharide vaccine (PPSV23) is not needed; if PCV15 is given, administer a dose of PPSV23 at least 8 weeks after the dose of PCV15 if the patient is age 2 years or older.

Last reviewed: November 15, 2024

Since the patient is asplenic, the second dose of the primary series of MenACWY should be given at least 8 weeks after the first dose. He will need a dose of MenACWY every 5 years for the rest of his life. The 3-dose series of MenB (whether Trumenba [Pfizer] or Bexsero [GSK]) should be completed. The first booster dose of MenB will be due one year after completion of the primary series and subsequent booster doses are recommended every 2–3 years for the rest of his life. The same MenB vaccine should be used for all doses in the series, including booster doses. People who receive Trumenba brand MenB vaccine have an option to receive MenABCWY (Penbraya, Pfizer) when both MenACWY and MenB vaccines are due at the same visit, as long as doses of Penbraya are spread out by at least 6 months. The patient has already received one dose of PCV20, in accordance with pneumococcal vaccination recommendations for immunocompromised adults younger than age 50, so no further doses are needed. Based on the patient’s age, only one dose of Hib vaccine is recommended, so no further doses are needed. The patient should receive influenza vaccine annually.

Any of these vaccines can be given at the same appointment.

Last reviewed: November 15, 2024

Three hepatitis B (HepB) vaccines are currently licensed and available in the United States. All of them contain recombinant hepatitis B surface antigen (HBsAg) produced in yeast cells. From 2021 until late 2024, PreHevbrio (VBI Vaccines), an additional 3-dose HepB vaccine option for adults, was available. PreHevbrio is a 3-antigen recombinant hepatitis B vaccine derived from mammalian (Chinese hamster ovary) cells; its use was discontinued for business reasons following VBI’s 2024 bankruptcy filing.

HepB vaccines are available as HepB-only formulations; two of them are also available in combination with other vaccines. Heplisav-B (Dynavax) is approved only for people 18 years of age and older. Engerix-B (GSK) and Recombivax HB (Merck) are approved for vaccination starting at birth and are available in both pediatric and adult formulations. For the 3-dose series of Engerix-B or Recombivax HB, people 0 through 19 years of age receive a 0.5 mL dose regardless of their height or weight; people 20 years of age and older receive a 1.0 mL dose.

Three combination vaccines that contain HepB are available in the United States. Pediarix (GSK) is approved for children 6 weeks through 6 years of age and contains HepB, DTaP, and inactivated poliovirus (IPV). Twinrix (GSK) is approved for adults 18 years of age and older and contains HepB and inactivated hepatitis A virus (HepA). Vaxelis (MCM Company) is approved for use in children 6 weeks through 4 years of age and contains HepB, DTaP, Hib, and IPV.

Last reviewed: January 17, 2025

Because of the limited number of serogroups covered by PCV7 (which was used in the United States between 2000 and 2010), CDC recommends that doses of PCV7 should be ignored for the purposes of calculating the current pneumococcal vaccination needs of an older teen or adult patient at increased risk for pneumococcal disease. For example, a person at high risk of pneumococcal disease who received a complete series of PCV7 vaccination in early childhood should follow the vaccination recommendations for someone with their condition who has not received any doses of pneumococcal conjugate vaccine.

Last reviewed: November 13, 2024


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Last reviewed: March 28, 2023

Both PCV15 and PCV20 are recommended as pneumococcal vaccination options for children age 6 weeks and older as well as for older children age 6 through 18 years with certain medical conditions or other risk factors for pneumococcal disease. ACIP no longer recommends PCV13 for children or adults; however, PCV13 may be given as previously recommended if it is the only PCV available and the recipient would otherwise go without vaccination. Pneumococcal polysaccharide vaccine (PPSV23) is recommended as an option for some children age 2 years and older who have certain underlying medical conditions and who have not had (or do not have the option of receiving) PCV20.

Details of the recommendations can be found in the ACIP recommendations at www.cdc.gov/mmwr/volumes/72/wr/pdfs/mm7239a5-H.pdf (for PCV20) and www.cdc.gov/mmwr/volumes/71/wr/pdfs/mm7137a3-H.pdf (for PCV15). These recommendations are to be used in conjunction with CDC clinical considerations for the use of pneumococcal vaccines at: www.cdc.gov/pneumococcal/hcp/vaccine-recommendations/index.html.

A summary of these recommendations can also be found at www.immunize.org/wp-content/uploads/catg.d/p2016.pdf. Immunize.org has developed standing orders for pneumococcal vaccination of children and teens at www.immunize.org/wp-content/uploads/catg.d/p3086.pdf.

Last reviewed: November 13, 2024

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