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.
How to Find Your Answer
Note: Selecting a filter subcategory may also return results from the primary category. We are working with our vendor to resolve this error.
Some filter options may become disabled as you narrow your selections.
Filters are easily added and removed. Click or tap on the X to remove individual filters or choose “Reset All Filters” to remove all filters.
Results (1379)
Scheduling Vaccines
We gave a dose of vaccine too soon after the previous dose. When can we give another (valid) dose?
If vaccines are given too close together, it can result in a less than optimal immune response. However, in most instances, a difference of a few days is unlikely to have a negative effect on immune response. With the exception of rabies vaccine, ACIP allows a grace period of 4 days (i.e., vaccine doses administered up to 4 days before the recommended minimum interval or age can be counted as valid). However, if a dose was administered 5 or more days earlier than the recommended minimum interval between doses, it is not valid and must be repeated. The repeat dose should be spaced after the invalid dose by the recommended minimum interval. Note that for hepatitis A vaccination, if the second dose is administered too early and must be repeated, the recommended interval between the invalid dose and the repeat dose is 6 months; however, if the repeat dose is administered earlier than 6 months no further doses are recommended as long as the interval between the first and final dose is at least 6 months.
If the first dose in a series is given 5 days or more before the recommended minimum age, the dose should be repeated on or after the date when the child reaches at least the minimum age. If the vaccine is a live vaccine, ensuring that a minimum interval of 28 days has elapsed from the invalid dose is recommended. Avoid such errors by knowing the minimum intervals and ages for routinely given vaccines. You can look up such information in the ACIP “General Best Practices Guidelines for Immunization”, available at www.cdc.gov/vaccines/hcp/imz-best-practices/timing-spacing-immunobiologics.html, Table 3-2.
The 4-day “grace period” should not be used when scheduling future vaccination visits, and should not be applied to the 28-day interval between different live parenteral vaccines not administered at the same visit. It should be used primarily when reviewing vaccination records (for example, when evaluating a vaccination record prior to entry to daycare or school).
Last reviewed:
June 6, 2023
Pneumococcal
Vaccine Products
How effective is pneumococcal polysaccharide vaccine at preventing pneumococcal carriage or disease?
According to CDC, more than 80% of healthy adults who receive PPSV23 develop antibodies against the serotypes contained in the vaccine that persist for at least 5 years. Older adults and people with some chronic illnesses or immunodeficiency may not respond as well and their antibody levels may decline more quickly.
Overall, the vaccine is 60% to 70% effective in preventing invasive pneumococcal disease caused by serotypes in the vaccine. PPSV23 shows less effectiveness among immunocompromised people; however, because of their increased risk of invasive pneumococcal disease, CDC recommends PPSV23 for people in these groups who receive PCV15. There has not been consensus regarding the ability of PPSV23 to prevent non-bacteremic pneumococcal pneumonia; however, recent observational studies reported 21%–46% effectiveness against PPSV23-type pneumococcal pneumonia when PPSV23 was given less than 5 years before illness onset.
Unlike conjugate vaccines, PPSV23 vaccination has not been shown to decrease nasal carriage of pneumococcal bacteria among those vaccinated.
Last reviewed:
November 13, 2024
Zoster (Shingles)
Vaccine Recommendations
To whom should zoster vaccine be given?
Shingrix is recommended for the prevention of herpes zoster and related complications for immunocompetent adults 50 years of age and older, including those who previously received Zostavax. On October 20, 2021, ACIP recommended 2 doses of RZV for the prevention of herpes zoster and related complications in adults age 19 years or older who are or will be immunodeficient or immunosuppressed because of disease or therapy.
ACIP published its recommendations for the use of recombinant zoster vaccine in adults age 19 years or older who are or will be immunocompromised in January 2022: www.cdc.gov/mmwr/volumes/71/wr/pdfs/mm7103a2-H.pdf.
Last reviewed:
March 9, 2022
MMR (Measles, Mumps, and Rubella)
Vaccine Recommendations
Given the risk of outbreaks of measles in the U.S., should all healthcare personnel, including those born before 1957, have 2 doses of MMR vaccine?
Although birth before 1957 is considered acceptable evidence of measles immunity for routine vaccination, healthcare facilities should consider vaccinating unvaccinated healthcare personnel (HCP) born before 1957 who do not have laboratory evidence of measles immunity, laboratory confirmation of disease, or vaccination with 2 appropriately spaced doses of MMR vaccine.
However, during a local outbreak of measles, all healthcare personnel, including those born before 1957, are recommended to have 2 doses of MMR vaccine at the appropriate interval if they lack laboratory evidence of measles.
Healthcare facilities should check with their state or local health department’s immunization program for guidance. Access contact information here: www.immunize.org/coordinators.
Last reviewed:
June 19, 2023
Polio
We occasionally encounter older teens who received 4 doses of inactivated polio vaccine (IPV) before their fourth birthday. Should we recommend a 5th dose of IPV for these children?
CDC published a revised ACIP recommendation for IPV on August 6, 2009, to include a dose given at age 4 through 6 years (and at least 6 months after the preceding dose), regardless of the number of doses given before the fourth birthday. In general, you do not need to administer an additional IPV dose to older teens (or adults) who had already completed a routine 4-dose schedule of polio vaccination before their fourth birthday before the change was published in August 2009; however, if a dose given after the fourth birthday is needed for compliance with state requirements, you may want to check with your state immunization program or immunization registry manager to see what they accept/expect in this case. Contact information for state immunization managers can be found at www.immunize.org/coordinators.
Last reviewed:
July 23, 2023
Varicella (Chickenpox)
Vaccine Recommendations
Can varicella vaccine be used as postexposure prophylaxis for a 9-month-old who was exposed to herpes zoster?
Varicella vaccine is neither approved nor recommended for children younger than age 12 months. Assuming that the child is not immunocompromised, varicella zoster immune globulin (VariZIG) is also not recommended.
ACIP does not have a recommendation for acyclovir for varicella postexposure prophylaxis. The American Academy of Pediatrics provide some guidance on this issue in the current edition of the Red Book.
Last reviewed:
May 16, 2023
Combination Vaccines
DTaP-IPV-HepB (Pediarix, GSK)
Our nurses have been routinely giving Pediarix (DTaP-HepB-IPV) to toddlers who were overdue for their third doses of DTaP, IPV, and HepB. Recently someone told me that Pediarix is only intended for use at 2, 4, and 6 months of age. Did we err?
No. Pediarix is licensed for doses 1, 2, and 3 of the DTaP primary series through age 6 years.
Last reviewed:
January 27, 2025
Contraindications & Precautions
Is it necessary to routinely obtain a pregnancy test before administering any vaccines to young women?
No. Pregnancy tests prior to vaccination are not routinely recommended. However, patients of childbearing age should be asked about the possibility of their being pregnant prior to being given any vaccine for which pregnancy is a contraindication or precaution. The patient’s answer should be documented in the medical record. If the patient responds that they believe they may be pregnant, a test should be performed before administering vaccines not recommended or contraindicated in pregnancy.
Last reviewed:
August 29, 2022
Meningococcal ACWY
Vaccine Recommendations
Should college students be vaccinated against meningococcal disease with MenACWY vaccine? [Video]
If a healthy infant received one dose of Hib at 5 months, and another at 15 months, does he/she need any more doses?
No. If a healthy child receives a dose of Hib vaccine at 15 months of age or older, he or she does not need any further doses regardless of the number of doses received before 15 months of age.
Last reviewed:
January 21, 2025
Storage & Handling
Vaccine Storage Units
Is it okay to store medications and other biologic products in the same unit as vaccines?
CDC’s Vaccine Storage and Handling Toolkit states that if other medications and biological products must be stored in the same unit as vaccines, they must be clearly marked and stored in separate containers or bins from vaccines. Potentially contaminated items (e.g., blood, urine) should be properly contained and stored below vaccines due to risk of contamination from drips or leaks. The freezer of a household-grade unit may be used for non-vaccine, medical storage, so long as the use does not compromise the temperature range within the refrigerator compartment where vaccine is stored.
Last reviewed:
July 26, 2023
HPV (Human Papillomavirus)
Vaccine Recommendations
Are catch-up recommendations for the use of HPV vaccine different for males and females?
No. In June 2019, the Advisory Committee on Immunization Practices (ACIP) voted to recommend routine catch-up HPV vaccination of all previously unvaccinated or incompletely vaccinated males age 22 through 26, matching the recommendation for females. HPV vaccination recommendations now differ by age group only, not by biological sex. There is a routine recommendation for vaccination of all people 9 through 26 years of age and a shared clinical decision-making recommendation based on risk and preference for people 27 through 45 years of age.
Under section 564 of the Federal Food, Drug, and Cosmetic Act (FD&C Act), the FDA Commissioner may allow unapproved medical products or unapproved uses of approved medical products to be used in an emergency to diagnose, treat, or prevent serious or life-threatening diseases or conditions caused by chemical, biological, radiological or nuclear threat agents when there are no adequate, approved, and available alternatives. Vaccines that receive an EUA may later be fully licensed by the FDA.
Last reviewed:
November 16, 2024
Meningococcal B
Vaccine Recommendations
Should college students be vaccinated against meningococcal serogroup B disease?
Several small outbreaks of meningococcal serogroup B disease have occurred on college campuses since 2013. However, the disease incidence in college students remains very low (0.03 cases per 100,000 college students age 18 to 24 years in 2020). ACIP does not routinely recommend MenB vaccine for college students. However, the recommendation for shared clinical decision-making applies to all college students age 16 through 23 years who may choose to receive MenB vaccine to reduce their risk of meningococcal serogroup B disease. In addition, some colleges and universities require MenB vaccination for incoming students.
If a college student completes the MenB vaccine series at least 6 months to 1 year before being identified as at risk during an outbreak, a single booster dose of the same brand can boost levels of protective antibodies within 1-2 weeks. The ability to be protected quickly during an outbreak by a single booster dose may be an important consideration for college students, families, and administrators when deciding about getting the MenB vaccine primary series.
Last reviewed:
November 15, 2024
Meningococcal ACWY
Vaccine Recommendations
Several healthy adult college students from outside the U.S. (ages 24 years and older) presented to our clinic. They will be living in a residence hall. None have a record of having received MenACWY. Should the receive a dose of MenACWY now?
Yes. One dose of MenACWY vaccine is recommended for all first-year college students who are or will be living in a residence hall if they are previously unvaccinated, have not received a dose of MenACWY since turning 16, or if their most recent dose (given after turning 16) was not given within the past 5 years.
Last reviewed:
November 15, 2024
RSV (Respiratory Syncytial Virus)
Vaccine Products
Can any of the three licensed RSV vaccines be used during pregnancy?
Only the RSVpreF vaccine, Abrysvo by Pfizer, is licensed and recommended for one-time use between 32 weeks and 36 weeks 6 days of gestation to prevent RSV-associated lower respiratory tract disease in infants younger than 6 months old. Do not use Arexvy (GSK) or mResvia (Moderna) during pregnancy. If a pregnant person received an RSV vaccine before the current pregnancy, do not use Abrysvo during this pregnancy. Instead, counsel them that a dose of nirsevimab (Beyfortus, Sanofi) will be needed to protect the infant from RSV after birth.
Last reviewed:
August 25, 2024
Pneumococcal
Vaccine Products
What are the recommendations for pneumococcal vaccination of children and adults?
The recommendations for pneumococcal vaccination of children and adults vary depending upon the specific vaccines available, and the recipient’s age, pneumococcal vaccination history, and medical or behavioral risk factors. CDC has summarized all of its recommendations at this site: www.cdc.gov/pneumococcal/hcp/vaccine-recommendations/index.html.
Which vaccines are recommended for healthcare personnel (HCP)?
ACIP recommends that people working in healthcare settings be vaccinated against COVID-19, influenza, hepatitis B, measles, mumps, rubella, varicella, and pertussis. Adults are generally assumed to have been vaccinated against polio in childhood; any adult known or strongly suspected of being unvaccinated against polio should be vaccinated. For measles, mumps, rubella, and varicella, serologic evidence of immunity is an acceptable substitute for documentation of vaccination. In addition, microbiologists working in a laboratory should receive vaccination against meningococcal ACWY and meningococcal serogroup B disease. In rare cases, some laboratory personnel should also receive a single polio vaccine booster and typhoid vaccines. For more information, refer to the current CDC recommended adult immunization schedule or the 2011 ACIP recommendations for immunization of healthcare personnel, www.cdc.gov/mmwr/pdf/rr/rr6007.pdf.
Last reviewed:
January 27, 2025
Administering Vaccines
General Issues
A 5-year-old is in the office for vaccines and is due for MMR, polio, varicella, and DTaP. Is there a specific order I should be giving these vaccines?
The Advisory Committee on Immunization Practices (ACIP) does not address this issue. There is no recommended order in which the vaccines should be given. A best practice strategy to decrease injection or procedural pain is to administer the vaccine that causes the most pain (stinging, for example) last. For more general information on vaccine administration, please see the vaccine administration chapter of Epidemiology and Prevention of Vaccine-Preventable Diseases at www.cdc.gov/pinkbook/hcp/table-of-contents/chapter-6-vaccine-administration.html.
Last reviewed:
February 27, 2025
Documenting Vaccination
If my state has an Immunization Information System (IIS, or registry) do I still need to give the patient a vaccine record card?
Patient-held cards are an important part of a person’s medical history. The person may move to another state or need medical care at a facility within or outside the state without access to the IIS in which their records are documented, and the personal record may be the only vaccination record available.
Last reviewed:
February 16, 2025
Vaccine Safety
Is there any harm in giving an extra dose of MMR to a child of age seven years whose record is lost and the mother is not sure about the last dose of MMR?
No. In general, although it is not ideal, receiving extra doses of vaccine poses no medical problem. Receiving excessive doses of tetanus toxoid (e.g., DTaP, DT, Tdap, or Td) can increase the risk of a local adverse reaction, however. For details, see Extra Doses of Vaccine Antigens in the ACIP’s “Best Practice Guidelines for Immunization” at www.cdc.gov/vaccines/hcp/imz-best-practices/timing-spacing-immunobiologics.html.
Vaccination providers frequently encounter people who do not have adequate documentation of vaccinations. Providers should only accept written, dated records as evidence of vaccination. With the exception of influenza vaccine and pneumococcal polysaccharide vaccine, self-reported doses of vaccine without written documentation should not be accepted. An attempt to locate missing records should be made whenever possible by contacting previous healthcare providers, reviewing state or local immunization information systems, and searching for a personally held record.
If records cannot be located or will definitely not be available anywhere because of the patient’s circumstances, children without adequate documentation should be considered susceptible and should receive age-appropriate vaccination. Serologic testing for immunity is an alternative to vaccination for certain antigens (e.g., measles, rubella, hepatitis A, diphtheria, and tetanus).
Last reviewed:
August 31, 2022
Rabies
My patient did not return for his postexposure rabies vaccine dose on day 7. How should I manage his series now?
Every attempt should be made to adhere to the recommended vaccination schedules. Once vaccination is initiated, delays of a few days for individual doses are unimportant, but the effect of longer lapses of weeks or more is unknown. Most interruptions in the vaccine schedule do not require reinitiation of the entire series. For most minor deviations from the schedule, vaccination can be resumed as though the patient were on schedule. For example, if a patient misses the dose scheduled for day 7 and presents for vaccination on day 10, the day 7 dose should be administered that day and the schedule resumed, maintaining the same interval between doses. In this scenario, the remaining doses would be administered on days 17 and 31. When substantial deviations from the schedule occur, immune status should be assessed by performing serologic testing 7–14 days after administration of the final dose in the series. Postexposure prophylaxis with rabies vaccine is described in detail at www.cdc.gov/mmwr/pdf/rr/rr5902.pdf.
Last reviewed:
May 14, 2023
Polio
If an immigrant infant has a record of 1 or 2 doses of oral polio vaccine (OPV) in their country of origin how many more doses of IPV should be given?
Polio vaccine given outside the United States is valid if written documentation indicates that all doses were given after 6 weeks of age and the vaccine received was IPV or trivalent OPV (tOPV). Only trivalent polio vaccine counts toward the U.S. schedule. No doses of OPV given since April 1, 2016, count toward the U.S. polio vaccination schedule because, on that date, all countries routinely using tOPV switched to bivalent OPV. Please see other detailed answers concerning details on assessment of OPV doses by the date of administration.
If both tOPV and IPV were or will be administered as part of a series, the total number of doses needed to complete the series is the same as that recommended for the U.S. IPV schedule. If the child is younger than 4 years of age a total of 4 doses of polio vaccine are recommended. If the child is currently 4 years of age or older, a total of 3 doses completes the series. A minimum interval of 4 weeks should separate doses in the series, with the final dose administered on or after the fourth birthday and at least 6 months after the previous dose. If only tOPV was administered, and all doses were given before 4 years of age, 1 dose of IPV should be given at 4 years of age or older, at least 6 months after the last tOPV dose.
Last reviewed:
July 23, 2023
Rotavirus
Vaccine Recommendations
Can preterm infants receive rotavirus vaccine?
ACIP supports vaccination of preterm infants according to the same schedule and precautions as full-term infants and under the following conditions: if the infant’s chronological age meets the age requirements for rotavirus vaccine (for example, age 6 weeks to 14 weeks 6 days for dose #1), the infant is clinically stable, and the vaccine is administered at the time of discharge from the hospital or after discharge from the hospital.
Last reviewed:
June 7, 2023
Hepatitis A
Disease Issues
Are people with chronic liver disease at higher risk of acquiring hepatitis A virus (HAV) infection?
No. People with chronic liver disease are not at increased risk for acquiring HAV infection. However, they are at an increased risk for life-threatening, fulminant (severe and sudden) hepatitis if they become infected with hepatitis A. People considered to have chronic liver disease include those with hepatitis B or C infection, cirrhosis, fatty liver disease, alcoholic liver disease, and autoimmune hepatitis.
Last reviewed:
June 25, 2023
Scheduling Vaccines
Two live virus vaccines can be given on the same day. How do you define “day”?
The “same day” generally means at the same visit. This interval has not been precisely defined and probably will never be since it would be extremely difficult to study in order to develop an evidence-based recommendation. Immunization programs (and their computer systems) likely define this differently. It seems reasonable that if two vaccines were given on the same date then they would both be valid.
Last reviewed:
June 6, 2023
Dengue
Vaccine Recommendations
Is Dengvaxia recommended for travelers to dengue endemic areas?
No, it is not. It is only recommended for children and teens ages 9 through 16 who reside in dengue endemic areas.
Last reviewed:
January 17, 2025
Zoster (Shingles)
Vaccine Recommendations
My clinic cannot consistently keep Shingrix in stock due to high demand. How should we handle challenges ensuring patients receive a second dose?
Clinicians and patients should make every effort to ensure that two doses of Shingrix are administered within the recommended interval of 2 to 6 months. If more than 6 months have elapsed since the first dose of Shingrix, administer the second dose when possible. Do not restart the vaccine series.
Who should be tested for anti-HBs after vaccination?
Serologic testing for immunity is not necessary or recommended after routine vaccination of infants, children, or adults. Testing for anti-HBs after vaccination is recommended for the following groups whose subsequent clinical management depends on knowledge of their immune status:
Infants born to HBsAg-positive women and infants born to women whose HBsAg status remains unknown (for example, infants surrendered shortly after birth); postvaccination serologic testing should consist of testing for anti-HBs and HBsAg and should not occur before age 9 months
Healthcare professionals and public safety workers at risk for blood or body fluid exposure
Hemodialysis patients (and other persons who might require outpatient hemodialysis), people living with HIV, and other immunocompromised people (such as hematopoietic stem-cell transplant [HSCT] recipients or people receiving chemotherapy), to determine the need for revaccination and the type of follow-up testing, and
Sex partners of HBsAg-positive people, to determine if they have not achieved immunity and will need revaccination and to continue to use other methods of protection against HBV infection.
Testing of individuals other than infants should be performed 1–2 months after administration of the final dose of the vaccine series using a method that allows determination of a protective concentration of anti-HBs (10 mIU/mL or higher). Testing of infants should take place after administration of the final dose of the vaccine series when the infant is age 9 through 12 months. Testing should not be done earlier than 9 months to avoid inadvertent detection of HBIG administered at birth and to maximize the likelihood of detecting HBV infection, if present.
Last reviewed:
January 17, 2025
Varicella (Chickenpox)
Vaccine Recommendations
If a healthcare worker does not have a history of varicella vaccination or disease but has had a clinically diagnosed case of shingles, does she or he still need varicella vaccination?
No. A healthcare provider’s diagnosis or verification of a history of shingles is acceptable evidence of immunity to varicella. According to ACIP, acceptable evidence of varicella immunity in healthcare personnel includes (1) documentation of 2 doses of varicella vaccine given at least 28 days apart, (2) history of varicella or herpes zoster based on clinician diagnosis, (3) laboratory evidence of immunity, or (4) laboratory confirmation of disease.
Last reviewed:
May 16, 2023
Combination Vaccines
DTaP-IPV-HepB (Pediarix, GSK)
We have been giving Pediarix (DTaP-HepB-IPV) to children who are overdue for DTaP #4, IPV #3, and HepB #3. Is this an acceptable practice?
No. Pediarix is intended to be used only for doses 1, 2, or 3 of the DTaP primary series; consequently, using Pediarix for DTaP #4 is off-label and not recommended. You should take measures to prevent this error in the future. The DTaP, IPV, and HepB doses given in this scenario do not need to be repeated as long as you met the recommended minimum intervals for each vaccine component (DTaP, IPV, HepB). If you did meet the minimum intervals, the doses should be counted as valid.
Last reviewed:
January 27, 2025
Contraindications & Precautions
Which vaccines are recommended to be given postpartum to mothers of newborns before hospital discharge?
The following vaccines are recommended for new mothers before they leave the hospital: (1) mothers without documentation of previous Tdap vaccination need a dose to protect themselves; (2) mothers who did not receive influenza vaccination during pregnancy need to be vaccinated if it is still influenza vaccination season (October through March); (3) mothers who tested susceptible to rubella on prenatal testing need MMR vaccine even if they have 1 or 2 documented doses of MMR in their medical record; (4) mothers who are not immune to chickenpox need 2 doses of varicella vaccine – the first dose before hospital discharge and the second dose 4 to 8 weeks after the first dose.
Last reviewed:
August 29, 2022
Diphtheria
Vaccine Recommendations
Pertussis
Vaccine Recommendations
Tetanus
Vaccine Recommendations
As a pediatrician, I am concerned about protecting my newborn patients from pertussis, especially given the recent outbreaks in my community where infants have died. How many doses of pediatric diphtheria-tetanus-acellular pertussis (DTaP) vaccine does an infant need before she or he is protected from pertussis?
Vaccine efficacy is 80%–85% following 3 doses of DTaP vaccine. Efficacy data following just 1 or 2 doses are lacking but are likely lower. The most effective way to prevent pertussis in early infancy is to vaccinate the mother between 27 and 36 weeks’ gestation. Antipertussis antibodies generated by the mother’s immune system are passed across the placenta to the fetus. One dose of Tdap should be administered during each pregnancy, preferably between 27 and 36 weeks’ gestation. Available data suggest that vaccinating closer to 27 weeks will maximize passive antibody transfer to the infant. A CDC evaluation found Tdap vaccination during the third trimester of pregnancy prevents 78% of pertussis cases in infants younger than 2 months of age and that maternal vaccination reduces the risk of infant hospitalization for pertussis by 90% (www.cdc.gov/pertussis/hcp/vaccine-recommendations/vaccinating-pregnant-patients.html).
Last reviewed:
March 31, 2022
MMR (Measles, Mumps, and Rubella)
Vaccine Recommendations
If there is an outbreak in my area, can we vaccinate children younger than 12 months?
MMR can be given to children as young as 6 months of age who are at high risk of exposure such as during international travel or a community outbreak. However, doses given BEFORE 12 months of age cannot be counted toward the 2-dose series for MMR.
Last reviewed:
March 16, 2025
Diphtheria
Vaccine Recommendations
Pertussis
Vaccine Recommendations
Tetanus
Vaccine Recommendations
How many doses of pediatric diphtheria-tetanus-acellular pertussis, or DTaP, vaccine does an infant need before she or he is protected from pertussis? [Video]
Several healthy adult college students from outside the U.S. (ages 24 years and older) presented to our clinic. They will be living in a residence hall. None have a record of having received vaccination against meningococcal ACWY disease. Should they receive a dose of MenACWY now? [Video]
Please explain the federal requirements for all healthcare providers that administer vaccines under the National Childhood Vaccine Injury Act.
The National Childhood Vaccine Injury Act (NCVIA), enacted in 1986, set forth 3 basic requirements for all vaccination providers, which are:
Providers must give the patient (or parent/legal representative of a minor) a copy of the relevant federal “Vaccine Information Statement” (VIS) for the vaccine they are about to receive.
Providers must record certain information about the vaccine(s) administered in the patient’s medical record or a permanent office log.
Providers must document any adverse event following the vaccination that the patient experiences and that becomes known to the provider, whether or not it is felt to be caused by the vaccine, and submit the report to the Vaccine Adverse Event Reporting System (VAERS) at https://vaers.hhs.gov.
Last reviewed:
February 16, 2025
HPV (Human Papillomavirus)
Vaccine Recommendations
What are the recommendations for use of HPV vaccine in people age 27 through 45 years?
Catch-up HPV vaccination is not recommended for adults older than 26 years of age. Instead, shared clinical decision-making regarding HPV vaccination is recommended for some adults aged 27 through 45 years who are not adequately vaccinated and want to be protected from ongoing risk of acquiring new HPV infection.
Ideally, HPV vaccine should be administered before potential exposure to HPV through sexual contact.
Last reviewed:
March 2, 2024
Hepatitis B
Tests & Interpretation
I have a patient who is positive for anti-HBc (hepatitis B core antibody) but negative for other hepatitis B serologic markers. Should he receive hepatitis B vaccine?
Some isolated positive anti-HBc results are false positives (it is the most common false positive HBV marker). If that can be established, the individual can and likely should be vaccinated, assuming there is an indication or desire to be protected. If the positive anti-HBc is believed to be a true positive, the individual would not require vaccination since they have already (presumably) had HBV infection. Isolated positive anti-HBc could indicate low-level chronic infection. In an infant isolated anti-HBc could indicate passive transfer of antibody from a mother who is HBsAg positive, which is why anti-HBc testing of infants is not recommended.
We run immunization clinics at the local jail, which has a living arrangement comparable to a college residential hall. In this setting, would you recommend vaccinating incarcerated individuals against meningococcal ACWY disease as is recommended for people living in a college dormitory?
ACIP does not identify incarceration as an indication for meningococcal ACWY vaccination. Providers are always free to use their clinical judgment in situations not addressed by ACIP.
Last reviewed:
November 15, 2024
Pneumococcal
Vaccine Products
What are the different serotypes of S. pneumoniae targeted by different pneumococcal vaccines?
S. pneumoniae bacteria are serotyped based on the polysaccharides in the outer capsule of the bacteria. Serotypes vary in how common they are and in what percentage of pneumococcal disease they cause.
Among the PCV vaccines, PCV13 includes serotypes: 1, 3, 4, 5, 6A, 6B, 7F, 9V, 14, 18C, 19A, 19F and 23F. PCV15 includes all PCV13 serotypes plus 22F and 33F. PCV20 includes all PCV15 serotypes plus 8, 10A, 11A, 12F, and 15B. PPSV23 vaccine does not contain serotype 6A, but contains 19 other serotypes present in PCV20, plus serotypes 2, 9N, 17F, and 20.
PCV21 is designed to target additional serotypes causing a significant proportion of disease in adults that are not prevented by the vaccines approved for children. It does not contain 10 serotypes found in other pneumococcal vaccines approved for children (1, 4, 5, 6B, 9V, 14, 18C, 19F, 23F, 15B, or 2). Instead, it contains an additional 11 serotypes not found in PCV20: 9N, 17F, 20, 15A, 15C, 16F, 23A, 23B, 24F, 31, and 35B. Because of these differences, CDC estimates that PCV20 targets serotypes that cause between 54% and 65% of invasive pneumococcal disease (IPD) in adults, and PCV21 targets serotypes that cause between 77% and 85% of IPD in adults.
PCV13
PCV15
PCV20
PPSV23
PCV21
1
x
x
x
x
3
x
x
x
x
x
4
x
x
x
x
5
x
x
x
x
6A
x
x
x
x
6B
x
x
x
x
7F
x
x
x
x
x
9V
x
x
x
x
14
x
x
x
x
18C
x
x
x
x
19A
x
x
x
x
x
19F
x
x
x
x
23F
x
x
x
x
22F
x
x
x
x
33F
x
x
x
x
8
x
x
x
10A
x
x
x
11A
x
x
x
12F
x
x
x
15B
x
x
2
x
9N
x
x
17F
x
x
20
x
x
15A
x
15C
x
16F
x
23A
x
23B
x
24F
x
31
x
35B
x
Last reviewed:
November 13, 2024
Influenza
Vaccine Recommendations
What influenza vaccines may be used in adults for the 2024-25 season?
All nine 2024-25 influenza vaccines approved for adults are trivalent, containing two influenza A strains and one influenza B strain.
There are five injectable inactivated influenza vaccine (IIV) options approved for use in all adults age 18 years or older. Four egg-based standard dose IIV vaccines (SD-IIVs) and one cell culture-based one (ccIIV) are available, all given as an intramuscular (IM) injection:
One egg-based live attenuated nasal spray vaccine, FluMist (LAIV, AstraZeneca), is an option for healthy, non-pregnant adults through age 49 years: 0.2 mL (given intranasally, 0.1 mL in each nostril).
Three injectable vaccines, all given IM, are ACIP-preferred options for adults age 65 years or older:
Recombinant influenza vaccine, Flublok (RIV, Sanofi): 0.5 mL/dose, licensed for use in adults age 18 or older
Fluzone High-Dose (egg-based HD-IIV, Sanofi): 0.5 mL/dose, licensed for adults age 65 years and older
Fluad (egg-based aIIV with MF59 adjuvant, CSL Seqirus): 0.5 mL/dose, licensed for adults age 65 years and older
Although licensed by FDA for use in adults age 65 years or older, ACIP also recommends off-label use of Fluzone HD or Fluad as acceptable options for influenza vaccination of solid organ transplant recipients age 18 through 64 years who are on immunosuppressive medication regimens, without a preference over other age-appropriate IIVs or RIV.
Last reviewed:
August 11, 2024
Hib (Haemophilus influenzae type b)
Scheduling & Administration
Since the booster dose of Hib vaccine can be given at 12–15 months, is it still necessary to “boost” two months later if the first dose was given at 12–14 months?
If the child received a primary series (2 or 3 doses, depending upon the product) of Hib vaccine in the first year of life, then the final (booster) dose of the series may be given as early as 12 months, provided at least 2 months have passed since the last dose. An unvaccinated 12–14-month-old child should receive one dose as a primary series, and a booster dose 2 months later. Unvaccinated healthy children 15–59 months of age need only a single dose of any licensed conjugate Hib vaccine. Some high-risk children 15–59 months of age are recommended for two doses of Hib vaccine based on previous history of incomplete vaccination; these special situations are reviewed in the Hib notes section of the schedule: www.cdc.gov/vaccines/hcp/imz-schedules/child-adolescent-notes.html.
Last reviewed:
January 21, 2025
Dengue
Vaccine Recommendations
I have a patient who is 24 years old and lives in Puerto Rico. He had confirmed dengue in 2014 and is requesting dengue vaccination. Should we vaccinate him?
No. Dengvaxia is FDA-licensed only for children and teens ages 6 years through 16 years.
Last reviewed:
January 17, 2025
Vaccine Recommendations
Where can I get the most up-to-date information on vaccination recommendations for people who travel outside the U.S.?
You can get this information from CDC’s Travel Health website at wwwnc.cdc.gov/travel/. CDC also publishes Health Information for International Travel (a.k.a. the “Yellow Book”) as a reference for those who advise international travelers of health risks. The Yellow Book is written primarily for healthcare providers, although others might find it useful. The contents of the book are available on the CDC Travel Health website. The book can also be ordered in print form. See the Yellow Book at wwwnc.cdc.gov/travel/page/yellowbook-home.
Both MenB vaccine products, Trumenba (MenB-Fhbp, Pfizer) and Bexsero (MenB-4C, GSK) are routinely given as a 2-dose series with doses administered at least 6 months apart. A 3-dose schedule is recommended for people who need rapid protection against MenB due to an increased risk of MenB disease. For the 3-dose schedule, dose 2 is given 1-2 months after dose 1 and dose 3 at least 6 months after dose 1.
Penbraya (MenABCWY, Pfizer) contains MenB-Fhbp (Trumenba) and is given as two doses, 6 months apart, when vaccination against all 5 serogroups is needed. For adolescents and adults not at increased risk (who need only one dose of MenACWY vaccine), if Penbraya is used, Trumenba should be administered to complete the 2-dose MenB series. For people age 10 years or older at increased risk of meningococcal disease, Penbraya may be used for additional MenACWY and MenB doses (including booster doses) when both vaccines would be given on the same clinic day and at least 6 months have elapsed since most recent Penbraya dose.
In August 2024, FDA revised the licensed schedule for Bexsero to be the same as the schedule and dosing intervals of the other MenB vaccine product, Trumenba. The change was made due to evidence of a small, but significant, improvement in the immune response to Bexsero when 2 doses were given 6 months apart, instead of 1 month apart, as previously licensed. As with Trumenba, a third dose of Bexsero is due, at least 4 months after the second dose and 6 months after the first, if dose 2 is given less than 6 months after dose 1. No additional doses are recommended for people who previously completed the 2-dose Bexsero series using a 1-month interval as licensed and recommended at the time.
Last reviewed:
November 15, 2024
Contraindications & Precautions
Is it acceptable practice to administer MMR, Tdap, and influenza vaccines to a postpartum mom who received RhoGam after delivery?
Do we need to wait for the vaccine to reach room temperature before we administer it to a patient?
The live smallpox (vaccinia) vaccine, ACAM2000 (Emergent BioSolutions) and the non-replicating, live smallpox and mpox vaccine, Jynneos (Bavarian Nordic) should be brought to room temperature before use, according to the package inserts for these two products.
With the exception of these two vaccines, there is no recommendation to wait until a vaccine reaches room temperature before administration. The vaccine should be administered as soon as it is prepared.
Last reviewed:
February 27, 2025
Vaccine Safety
What is the Vaccine Adverse Event Reporting System (VAERS)?
As the name implies, VAERS is a nationwide system for monitoring adverse events following vaccination. VAERS is operated jointly by the FDA and the CDC since 1990.
Last reviewed:
August 31, 2022
Polio
Our adult patient has been accepted to a physician assistant program that requires polio vaccine for all students. She has 2 documented doses of oral polio vaccine (OPV) as a child, then recently had a dose of inactivated polio vaccine (IPV). How many more doses of IPV does she need to complete the series and on what schedule?
People who receive a mixed series of OPV and IPV should receive a total of either 3 or 4 doses depending on the age at the time of the last dose. In this case the recent dose of IPV can be counted as the third and final dose in the series. The minimum interval between the next-to-last and last doses in the polio vaccination series is 6 months and the last dose should be at age 4 years or older.
Last reviewed:
July 23, 2023
Storage & Handling
Vaccine Storage Units
Can you please guide me in finding storage containers and bins for vaccines?
CDC recommends the use of bins, baskets, or some other type of uncovered containers that allow for organization and air circulation for vaccines and diluents within the storage unit. Storage in boxes or bins can help maintain temperature longer, especially if power is lost. Perforated bins may allow for better air circulation around the vaccine, thus helping to maintain correct temperature.
CDC does not have a specific recommendation for brands of containers or bins for storage of vaccine. We recommend that you contact your state immunization program, as they may have suggestions for purchasing this equipment. If you are a Vaccines for Children (VFC) program provider, you should contact your immunization program to ensure that you are in compliance with VFC policy.
Last reviewed:
July 26, 2023
Rotavirus
Vaccine Recommendations
We have a 20-week-old infant who was born prematurely. The infant has never received rotavirus vaccine and is technically past the maximum age for first dose. Should we give rotavirus vaccine to this infant?
ACIP recommends vaccination of preterm infants according to the same schedule and precautions as full-term infants. In preterm infants (as in full-term infants), the maximum chronological age for the first dose is 14 weeks 6 days. Vaccination should not be initiated for infants aged 15 weeks 0 days or older because of insufficient data on safety of dose 1 of rotavirus vaccine in older infants. For more information, see page 19 of ACIP’s recommendations on rotavirus vaccination, available at www.cdc.gov/mmwr/PDF/rr/rr5802.pdf.
Last reviewed:
June 7, 2023
Rabies
Can a pregnant person receive rabies vaccine if exposed to rabies?
Yes. A pregnant person should receive rabies vaccine if indicated. No fetal abnormalities have been reported with the rabies vaccine. A pregnant person can receive routine pre-exposure vaccination against rabies if the risk of exposure is high.
Last reviewed:
August 30, 2020
Hepatitis A
Disease Issues
Please discuss the tests commonly used to diagnose hepatitis A.
Hepatitis A cannot be differentiated from other types of viral hepatitis on the basis of clinical or epidemiological features alone. Appropriate blood tests must be used.
Anti-HAV: Total antibody to HAV. This diagnostic test detects total antibody of both IgG and IgM subclasses of HAV. If positive, it indicates either acute or resolved infection.
IgG anti-HAV: IgG antibody is a subclass of anti-HAV. It appears early in the course of infection, remains detectable for the person’s lifetime and provides lifelong protection against disease. Its presence indicates immunity through either HAV infection or HepA vaccination.
IgM anti-HAV: IgM antibody is a subclass of anti-HAV. Its presence indicates a recent infection with HAV (6 months or less). It is used to diagnose acute (recently acquired) hepatitis A. Because of the risk of false positive IgM anti-HAV results, people should only be tested for IgM anti-HAV if they are symptomatic and suspected of having acute hepatitis A illness.
HAV RNA tests also may be used to diagnose acute infection through the direct detection of viral RNA in serum or stool.
Total anti-HAV, which appears early in the course of infection, remains detectable for the person’s lifetime and indicates lifelong protection against the infection/disease. To confirm a diagnosis of acute HAV infection, serologic testing for IgM anti-HAV is required. In the majority of persons, serum IgM anti-HAV becomes detectable 5 to 10 days before onset of symptoms and lasts about 6 months. However, there have been reports of persons who test positive for IgM anti-HAV for up to a year or more following infection. An educational program on the interpretation of hepatitis A serology is available on the CDC website at www.cdc.gov/hepatitis/hcp/training/.
Last reviewed:
June 25, 2023
Scheduling Vaccines
For the purpose of vaccine spacing, what constitutes a month: 28 days (4 weeks), 30 days, or 31 days?
For intervals of 3 months or less, you should use 28 days (4 weeks) as a “month.” For intervals of 4 months or longer, you should consider a month a “calendar month”: the interval from one calendar date to the next a month later. This is a convention that was introduced on the childhood schedule in 2002 and discussed in the paper “Evaluation of Invalid Vaccine Doses” (Stokley S, Maurice E, Smith PJ, et al. American Journal of Preventive Medicine, 2004; 26[1]: 34–40).
Last reviewed:
June 6, 2023
MMR (Measles, Mumps, and Rubella)
Vaccine Recommendations
How does being born before 1957 confer immunity to measles?
People born before 1957 lived through several years of epidemic measles before the first measles vaccine was licensed in 1963. As a result, these people are very likely to have had measles disease. Surveys suggest that 95% to 98% of those born before 1957 are immune to measles. Persons born before 1957 can be presumed to be immune. However, if serologic testing indicates that the person is not immune, at least 1 dose of MMR should be administered.
Last reviewed:
June 19, 2023
Zoster (Shingles)
Vaccine Recommendations
Should Shingrix be given to people who have already received Zostavax? If so, what interval should separate them?
Yes. ACIP recommends that people who previously received Zostavax receive 2 doses of Shingrix. The first dose of Shingrix may be given a minimum of 8 weeks after Zostavax.
Last reviewed:
March 9, 2022
Varicella (Chickenpox)
Vaccine Recommendations
I have a patient who is 52 years old and is immigrating to the U.S. She received a dose of recombinant zoster vaccine at age 50. The immigration requirements state she should receive 2 doses of varicella vaccine. Does she need additional varicella vaccine?
Recombinant zoster vaccine (RZV, Shingrix, GSK) does not count as the first of two doses of varicella vaccine. Shingrix is not licensed and has not been evaluated for the prevention of primary varicella infection. To meet the immigration requirements, you should give a dose of varicella vaccine now and a second dose at least 4 weeks later. The varicella vaccine doses will not be harmful and will allow your patient to meet the regulatory requirement.
Last reviewed:
May 16, 2023
Combination Vaccines
DTaP-IPV/Hib (Pentacel, Sanofi)
Please describe the combination vaccine DTaP-IPV/Hib (Pentacel) and how it should be used.
FDA licensed Pentacel in 2008 as a 4-dose series in infants and children at ages 2, 4, 6, and 15–18 months. It should not be used for any dose in the primary series for children age 5 years or older or as the booster dose for children ages 4 through 6 years. The DTaP-IPV component is supplied as a sterile liquid, which is used to reconstitute lyophilized (freeze-dried) ActHIB vaccine. The two components of the vaccine should be stored together in the carton to reduce the chance of giving one component of the vaccine without the other. The DTaP-IPV component should never be administered alone.
Last reviewed:
January 27, 2025
Diphtheria
Vaccine Recommendations
Pertussis
Vaccine Recommendations
Tetanus
Vaccine Recommendations
My 11-year-old patient received a dose of Tdap when he was 7 years old. He also received a dose of Td 6 months later in order to finish a primary series of tetanus-toxoid. Can I give him a dose of Tdap now?
Yes. The January 2020 ACIP updated statement on the use of Tdap (available at www.cdc.gov/mmwr/volumes/69/wr/pdfs/mm6903a5-H.pdf) states that a child who receives a dose of Tdap from age 7–9 years as part of the catch-up series (as in this case), should receive another dose of Tdap at age 11 or 12 years.
Last reviewed:
March 31, 2022
Meningococcal B
Vaccine Recommendations
Why did FDA change the dosing schedule for Bexsero (GSK) in August 2024, and do I need to recall my patients who received Bexsero under the old schedule?
In August 2024, FDA revised the licensed schedule for Bexsero to be the same as the schedule and dosing intervals of the other MenB vaccine product, Trumenba (Pfizer). The change was made due to evidence of a small, but significant, improvement in the immune response to Bexsero when 2 doses were given 6 months apart, instead of 1 month apart, as previously licensed. No additional doses are recommended for people who completed the 2-dose Bexsero series using a 1-month interval, as licensed and recommended at the time.
A 3-dose schedule of Bexsero (dose 2 given 1-2 months after dose 1, and dose 3 given at least 6 months after dose 1 and 4 months after dose 2) is recommended for people who require accelerated protection from meningococcal B disease (those at increased risk).
Under the current Bexsero and Trumenba schedules, any MenB vaccine recipient whose second dose is administered less than 6 months after dose 1 should receive a third dose at least 6 months after dose 1 and 4 months after dose 2.
Last reviewed:
November 15, 2024
Meningococcal B
Vaccine Recommendations
My patient with functional asplenia due to sickle cell disease inadvertently received MenB dose 3 too early, only 4 months after dose 1 and 3 months after dose 2. What do I do?
Dose 3 of a 3-dose MenB series should be administered at least 6 months after dose 1 and 4 months after dose 2. In this case, an additional (fourth) dose may be administered at least 4 months after the invalid, early dose 3 and 6 months after dose 1. Review the dosing error and the correct schedule with staff and take other appropriate measures to prevent this error from occurring in the future.
