Ask the Experts: All Questions

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Results (1372)

Since both Kinrix and Quadracel are licensed and recommended only for children ages 4 through 6 years, you should take measures to prevent this error in the future. However, you can count this as a valid dose for DTaP and IPV as long as you met the minimum interval between administering dose #3 and dose #4 of DTaP (6 months) and dose #2 and dose #3 of IPV (4 weeks).

Last reviewed: July 15, 2023

It is not recommended to remove the stopper from a vaccine vial before administering a vaccine to a person who has a severe life-threatening allergy to latex. The vaccine has already been exposed to the rubber stopper in the vial, which might be enough of an exposure to cause a reaction. These people should not be given the vaccine.

Last reviewed: August 29, 2022

Yes. You must initiate the series while the recipient is age 16 years, but you may complete the series even if the recipient turns 17 before the series is completed.

Last reviewed: January 17, 2025

Yes. The second dose was given more than 4 days before the minimum interval of 6 calendar months, so it is considered invalid and should be repeated. The repeat dose should be administered the proper minimum interval (6 months) after the invalid dose. If this repeat dose is inadvertently given less than 6 months after the invalid dose, it does not need to be repeated again as long as the interval between the initial HepA vaccine and the most recent dose is at least 6 calendar months.

Last reviewed: June 25, 2023

You should use condoms until a postvaccination blood test (hepatitis B surface antibody, or anti-HBs) shows that your partner is protected from HBV infection. The efficacy of latex condoms in preventing infection with HBV is unknown, but their proper use might reduce the risk of transmission. Your sexual partner should have the 2- or 3-dose series of HepB vaccine (depending on brand) and postvaccination blood testing 1 to 2 months after the last dose of vaccine. If your partner’s test shows adequate anti-HBs (at least 10 mIU/mL), then they should be protected against HBV infection.

Last reviewed: January 17, 2025

With the exception of COVID-19 vaccines, vaccines in multidose vials (MDVs) that do not require reconstitution contain preservatives and can be used through the expiration date printed on the label as long as the vaccine is not contaminated, unless indicated otherwise by the manufacturer. For example, inactivated polio vaccine in an MDV can be used through the expiration date on the vial. For some vaccines, the manufacturer specifies that once the MDV has been entered or the rubber stopper punctured, the vaccine must be used within a certain number of days. This is commonly referred to as the “beyond-use date” (BUD). Any vaccine not used within the BUD should be discarded. Specific information regarding the BUD can be found in the product information. For example, the package insert for some inactivated influenza vaccine indicates once the stopper of the MDV has been pierced, the vial must be discarded within 28 days. Package inserts for vaccines can be found at www.immunize.org/fda.

Be careful to follow current guidance from the manufacturer and CDC for how long an MDV of COVID-19 vaccine may be used after puncturing the vial. The COVID-19 vaccine MDVs do not contain preservatives and must be used within hours; specific times vary by product.

Last reviewed: July 26, 2023

Hib vaccine should be maintained at refrigerator temperature between 2°C and 8°C (36°F and 46°F). Manufacturer package inserts contain additional information and can be found at www.immunize.org/packageinserts. For complete information on best practices and recommendations please refer to CDC’s Vaccine Storage and Handling Toolkit at www.cdc.gov/vaccines/hcp/admin/storage/toolkit/storage-handling-toolkit.pdf.

Last reviewed: July 31, 2022

ACIP recommends vaccination with 3 doses of HPV vaccine for people age 9 through 26 years with primary or secondary immunocompromising conditions that might reduce cell-mediated or humoral immunity. Examples include B lymphocyte antibody deficiency, T lymphocyte complete or partial defects, HIV infection, malignant neoplasm, transplantation, autoimmune disease, or immunosuppressive therapy. In these circumstances, the 3-dose series is recommended even for those who initiate vaccination at age 9 through 14 years when the routine recommendation is for a 2-dose series.

Last reviewed: March 2, 2024

FluMist (LAIV, AstraZeneca) is currently approved by FDA only for healthy non-pregnant people age 2 through 49 years.

Last reviewed: August 11, 2024

Yes. It is acceptable to administer any of the three available RSV vaccines at the same time as other recommended vaccines, in accordance with CDC’s general best practice guidelines for immunization. This is especially important if you are concerned an unvaccinated patient will not return or if the patient’s immediate risk is high (such as when seasonal influenza, RSV, and COVID-19 are circulating). Coadministration might increase short-term side effects (greater reactogenicity), such as fever, soreness, body aches, or headache, especially when administering more than one vaccine containing a non-aluminum adjuvant designed to enhance the immune response. While these side effects are not unsafe, they may be unpleasant for a day or two. If you are confident that a patient will return, the patient may prefer to separate the administration of vaccines that are less time-sensitive (e.g., shingles vaccine) to reduce the likelihood of uncomfortable side effects. There is no specific minimum interval between non-live vaccines, so separation by just a few days is acceptable, if desired.

Last reviewed: August 25, 2024

CDC states that a person who moves to an older age group between vaccine doses should receive the vaccine product and dosage for the older age group for all subsequent doses.

Children who transition from age 4 years to age 5 years during the initial vaccination series should receive 1 dose of the 2024–2025 vaccine from the same manufacturer at the dosage authorized for children age 5–11 years on or after turning age 5 years.

Last reviewed: November 16, 2024

CDC recommends that adults who have ever had at least one dose of PPSV23 do not need another dose of PPSV23. They should receive one dose of any of the 3 recommended vaccine options: PCV15, PCV20, or PCV21, at least one year after their PPSV23 dose.

Last reviewed: November 13, 2024

ACIP does not recommend MenB vaccination for travel to countries in sub-Saharan Africa or to other countries for which MenACWY vaccine is recommended. Meningococcal disease in these areas is generally not caused by serogroup B.

Last reviewed: November 15, 2024


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Last reviewed: August 27, 2024

Children who transition from age 4 years to age 5 years during the initial vaccination series should receive 1 dose of vaccine from the same manufacturer at the dosage for children ages 5–11 years on or after turning age 5 years. This child should receive one dose of the 2024–2025 Moderna vaccine (no dose change is needed).

Last reviewed: November 16, 2024

Yes. Shingrix is not a live virus vaccine and does not interfere with the tuberculin skin test (TST): it may be administered any time before or after a TST. Administration of a live virus vaccine can interfere with a tuberculin skin test (TST). If the TST is not administered on the same day as a live virus vaccine, the TST should be delayed until 4–6 weeks after the vaccination.

Last reviewed: March 9, 2022

No, it is not considered necessary, but he may be vaccinated. Before implementation of the national measles vaccination program in 1963, virtually every person acquired measles before adulthood. So, this patient can be considered immune based on their birth year. However, MMR vaccine also may be given to any person born before 1957 who does not have a contraindication to MMR vaccination.

Routine testing of patients born before 1957 for measles-specific antibody is not recommended by CDC.

Last reviewed: June 19, 2023

Contrary to the information provided in the vaccine package insert, which states that pregnancy should be avoided for 3 months, the ACIP recommends that a wait of 1 month is sufficient.

Last reviewed: May 16, 2023

In 2020, CDC published revised recommendations for hepatitis A postexposure prophylaxis (PEP). Please see the complete PEP recommendations at www.cdc.gov/mmwr/volumes/69/rr/pdfs/rr6905a1-H.pdf, with special attention to Table 4 on page 19 and Appendix B: Provider Guidance on Risk Assessment for Hepatitis A Postexposure Prophylaxis, beginning on page 36.

Healthy people who have completed the HepA vaccination series at any time do not need additional PEP if they are exposed to HAV. People who have recently been exposed to HAV and who have not received HepA vaccine previously should receive PEP as soon as possible, within 2 weeks of exposure.

People age 12 months and older exposed to HAV within the past 14 days and who have not previously completed the HepA vaccine series should receive a single dose of HepA vaccine as soon as possible. In addition to vaccine, immune globulin (IG; 0.1 mL/kg) may be administered to people older than age 40 years depending on the providers’ risk assessment. For long-term immunity, the HepA vaccine series should be completed with a second dose at least 6 months after the first dose. However, the second dose is not necessary for PEP. A second dose should not be administered sooner than 6 calendar months after the first dose, regardless of HAV exposure risk.

People age 12 months or older who are immunocompromised or have chronic liver disease, and who have been exposed to HAV within the past 14 days and have not previously completed the HepA vaccination series, should receive both IG (0.1 mL/kg) and HepA vaccine at the same visit in a different anatomic site (for example, separate limbs) as soon as possible after exposure. For long-term immunity, the HepA vaccination series should be completed with a second dose at least 6 months after the first dose. However, the second dose is not necessary for PEP. A second dose should not be administered sooner than 6 calendar months after the first dose, regardless of HAV exposure risk.

People with HIV infection develop protective levels of antibody more slowly and are less likely to develop protective antibody levels after vaccination with HepA, especially if their CD4+ count is low at the time of vaccination. Protection following vaccination of a person with HIV may wane over time. Vaccine should be administered if the exposed individual is not fully vaccinated; however, CDC also advises clinicians to consider administering IG PEP to an individual with HIV after a high-risk exposure (such as a household or sexual contact) even if the individual has been fully vaccinated.

Twinrix contains half the amount of hepatitis A antigen as a standard single-dose adult HepA vaccine. Twinrix should not be used for PEP but may be used to confer protection to at-risk but not yet exposed persons during an outbreak.

Infants younger than age 12 months and persons for whom vaccine is contraindicated should receive IG (0.1 mL/kg) instead of HepA vaccine as soon as possible and within 2 weeks of exposure. MMR and varicella vaccines should not be administered sooner than 6 months after IG administration in order to avoid possible IG interference with the effectiveness of MMR and varicella vaccines.

Last reviewed: June 25, 2023

No. Only the number of doses indicated in the manufacturer’s package insert should be withdrawn from the vial. For some vaccines, the package insert also may indicate the maximum recommended number of punctures of the vial stopper. After the maximum number of doses has been withdrawn or the number of punctures of the stopper has met the recommended limit, the vial should be discarded, even if there is vaccine remaining in the vial and the expiration date has not been reached. Never use partial doses from two or more vials to obtain a dose of vaccine.

Last reviewed: July 26, 2023

Secondary cases of Hib disease (illness occurring within 60 days of contact with a patient) occur but are rare. Secondary attack rates are higher among household contacts younger than 48 months (2.1%), especially those younger than 12 months (6%) and younger than 24 months (3%). Data are conflicting on the risk for secondary illness among child care contacts, but it is thought to be lower than among household contacts. Rifampin is recommended for chemoprophylaxis because it achieves high concentrations in respiratory secretions and eradicates nasopharyngeal carriage in more than 95% of carriers.

Index patients who are treated with an antibiotic other than cefotaxime or ceftriaxone and are younger than 2 years of age should receive rifampin prior to hospital discharge. Because cefotaxime and ceftriaxone eradicate Hib colonization, prophylaxis is not needed for patients treated with either of these antibiotics.

Rifampin chemoprophylaxis is recommended for all household contacts in households with members younger than 4 years who are not fully vaccinated, households with a child younger than 12 months who has not completed the primary Hib series, or households with a contact who is an immunocompromised child regardless of that child’s vaccination status.

Rifampin chemoprophylaxis is recommended in child care settings when two or more cases of invasive Hib disease have occurred within 60 days and unimmunized or underimmunized children attend the facility. When prophylaxis is indicated, it should be prescribed for all attendees, regardless of age or vaccine status, and for child care providers. See the current AAP Red Book chapter on Haemophilus influenzae infections for more information on this issue.

There are no guidelines for control measures around cases of invasive nontype b H. influenzae disease. Chemoprophylaxis is not recommended for contacts of persons with invasive disease caused by nontype b H. influenzae because cases of secondary transmission of disease have not been documented.

Last reviewed: July 31, 2022

You can give rotavirus vaccine through a tube as long as the child is otherwise eligible.

Last reviewed: December 28, 2022

Kinrix (GSK) and Quadracel (Sanofi) brands of combination DTaP-IPV vaccine are licensed and recommended only for use in children ages 4 through 6 years, so you should take measures to prevent this error in the future. However, you can count the IPV dose as valid as long as it has met the minimum interval (4 weeks between doses except for the final dose in the series, which should be 6 months from the previous dose). With regard to the mistaken administration of the DTaP in a child older than age 6 years, the dose can be counted and does not need to be repeated with Td.

Last reviewed: July 15, 2023

The parent/caregiver should be notified immediately, warned of the possible increased risk for hospitalization and severe dengue if the person develops a subsequent natural dengue infection, and the need to seek immediate medical attention if warning signs of severe dengue develop.

Clinic staff should review the incident and ensure that staff members responsible for vaccination have had sufficient training and protocols are in place to prevent such errors.

The use of tools, such as the CDC prevaccination checklist, helps prevent such errors: (www.cdc.gov/dengue/resources/DVBD_FS_Vaccination_Checklist-508.pdf).

Last reviewed: January 17, 2025

Tetanus toxoid became commercially available in 1938, but was not widely used until the military began routine vaccination in 1941. Routine administration of tetanus toxoid was recommended by the AAP in 1944. Most World War II military personnel received at least one dose of tetanus toxoid, but civilian use, particularly for adults, did not increase until after the war. You should not assume the tetanus vaccination status for any person based on their age alone. Only a written record is acceptable proof of immunization. People without documentation should be assumed to be unimmunized.

Last reviewed: March 31, 2022

In its 2006 ACIP recommendation for the prevention of hepatitis B, an accelerated 4-dose series of hepatitis B vaccine (which was not FDA-approved) was described as acceptable. CDC experts no longer recommend that approach when travel is imminent because other FDA-approved options exist.

The simplest option is Heplisav-B: its 2-dose series may be completed in 4 weeks. If Heplisav-B is unavailable, another option is to give the first 3 doses of the 4-dose accelerated schedule for Twinrix (HepA-HepB) at 0 days, 7 days, and 21-30 days and to have her return for a fourth dose 12 months after dose 1. Although this patient does not need the hepatitis A component, a combination vaccine such as Twinrix may be used if a single antigen option is not feasible; the additional doses of hepatitis A vaccine are not harmful.

Last reviewed: January 17, 2025

No. The recommendation for a 3-dose HPV schedule does not apply to people with asplenia and neither does it apply to children 9 through 14 years with asthma, chronic granulomatous disease, chronic liver disease, chronic renal disease, central nervous system, anatomic barrier defects (such as a cochlear implant), complement deficiency, diabetes, heart disease or sickle cell disease unless the person is receiving immunosuppressive therapy for the condition.

Last reviewed: March 2, 2024

The patient should be vaccinated at least 2 weeks before the splenectomy, if feasible. If not, vaccinate as soon as possible. Depending upon products available, he has three options:

  • One dose of PCV20 or PCV21 alone, or
  • One dose of PCV15 followed by a dose of PPSV23

CDC recommends that if using the PCV15 and PPSV23 series, a minimum interval of 8 weeks can be considered for adults with an immunocompromising condition (including splenectomy), cochlear implant, or cerebrospinal fluid leak.

Last reviewed: November 13, 2024

No. Giving FluMist (LAIV) is not considered an aerosol-generating procedure.

Last reviewed: August 11, 2024

The safety and effectiveness of RSV vaccines have not been studied in infants. The family should be informed of the error, and nirsevimab (Beyfortus, Sanofi) should be administered as recommended as soon as feasible. CDC experts recommend that if you administer nirsevimab within 72 hours of the error, and you know where the RSV vaccine was injected, you should administer the nirsevimab in a different anatomic site. Facilities that stock RSV vaccine and nirsevimab should put systems and procedures in place to prevent this type of error, including staff training, clear labeling, and warnings in storage units. This medication error and any suspected adverse events following the error should be reported to the Vaccine Adverse Event Reporting System (VAERS) at https://vaers.hhs.gov.

For additional information about this type of error, see CDC’s COCA Now: Clinician Outreach Communication Activity update, dated January 22, 2024, at https://emergency.cdc.gov/newsletters/coca/2024/012224.html.

Last reviewed: August 25, 2024

ACIP recommends booster doses of MenB vaccines for people at increased risk of MenB disease. Booster doses should be administered to people in the following groups as long as increased risk remains:

  • People with functional or anatomic asplenia, including sickle cell disease
  • People with persistent complement component deficiency (an immune system disorder)
  • People who take a complement inhibitor (examples include eculizumab [Soliris], ravulizumab [Ultomiris], and sutimlimab [Enjaymo])
  • Microbiologists who routinely work with meningococcal isolates
  • Previously vaccinated people who are at risk during a meningococcal B disease outbreak

Because protective antibody levels produced by the primary series begin to wane within 1–2 years, the first booster dose is recommended one year after completion of the primary series, with subsequent booster doses every 2–3 years as long as increased risk remains. Previously vaccinated people identified by public health as being at risk during a meningococcal B outbreak should receive a booster dose if it has been at least one year since completion of their primary series, though depending upon the specific circumstances, public health may recommend a booster dose as little as 6 months after completion of the primary series.

Last reviewed: November 15, 2024

CDC states that if a person moves to an older age group between vaccine doses, they should receive the vaccine product and dosage for the older age group for all subsequent doses. 

Children who transition from age 11 years to age 12 years during the initial vaccination series should complete the 3-dose series using the dosage for people ages 12 years and older for all doses received on or after turning age 12 years: 

Moderna series: 2024–2025 Moderna, 0.5 mL/50ug 

Pfizer-BioNTech series: 2024­–2025 Pfizer-BioNTech, 0.3 mL/30 ug 

See www.cdc.gov/vaccines/covid-19/clinical-considerations/interim-considerations-us.html#table-02 for additional details.

Last reviewed: November 16, 2024


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Last reviewed: June 7, 2024

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, available at www.cdc.gov/mmwr/volumes/71/wr/pdfs/mm7103a2-H.pdf.

These recommendations should be implemented in conjunction with CDC’s Clinical Considerations for the Use of Recombinant Zoster Vaccine (RZV, Shingrix) in Immunocompromised Adults Aged >19 Years: www.cdc.gov/shingles/vaccination/immunocompromised-adults.html.

Last reviewed: March 9, 2022

To date, no adverse outcomes of pregnancy or in a fetus have been reported among people who inadvertently received varicella vaccine shortly before or during pregnancy. The risk of congenital varicella syndrome following varicella disease is small, so the risk of congenital anomalies following vaccination with live attenuated varicella zoster virus (VZV)-containing vaccine is probably very small.

Merck and the Centers for Disease Control and Prevention (CDC) jointly operated a pregnancy registry for women exposed to VZV-containing vaccines for seventeen years after the licensure of varicella vaccine. The registry was discontinued in 2013, having found no signals to indicate a risk of Congenital Varicella Syndrome or pattern of birth defects related to vaccination with VZV-containing vaccines. Healthcare providers may continue to report exposure to VZV-containing vaccines within 3 months of conception or during pregnancy by contacting Merck’s call center at 1-877-888-4231.

Last reviewed: May 16, 2023

First of all, make sure all your patients are fully vaccinated according to the U.S. immunization schedule.

In certain circumstances, MMR is recommended for infants age 6 through 11 months. Give infants this age a dose of MMR before international travel. In addition, consider measles vaccination for infants as young as age 6 months as a control measure during a U.S. measles outbreak. Consult your state health department to find out if this is recommended in your situation. Do not count any dose of MMR vaccine as part of the 2-dose series if it is administered more than 4 days before a child’s first birthday. Instead, repeat the dose when the child is age 12 months.

In the case of a local outbreak, you also might consider vaccinating children age 12 months and older at the minimum age (12 months, instead of 12 through 15 months) and giving the second dose 4 weeks later (at the minimum interval) instead of waiting until age 4 through 6 years.

Finally, remember that infants too young for routine vaccination and people with medical conditions that contraindicate measles immunization depend on high MMR vaccination coverage among those around them. Be sure to encourage all your patients and their family members to get vaccinated if they are not immune.

Last reviewed: June 19, 2023

Prevaccination serologic testing for HAV (measuring either total anti-HAV or IgG anti-HAV) is not indicated for children because of the low prevalence of infection in children. It also is not routinely recommended for adults but may be considered in some settings to reduce costs associated with vaccinating people who are already immune. Prevaccination testing should not be used if it poses a barrier to vaccinating susceptible people, especially people who are difficult to access.

Prevaccination testing is most likely to be cost-effective for adults who were either born in or lived for long periods of time in areas of the world with high or intermediate hepatitis A endemicity. When evaluating people from populations with high rates of previous HAV infection, vaccination history also should be obtained, if feasible. If testing or vaccination history is not available, do not postpone vaccinating. There is no harm in vaccinating a person who has had natural infection or previous doses of vaccine.

Last reviewed: June 25, 2023

Vaccine may be used through the last day of the month indicated on the expiration date. After that, do not use it. Monitor your vaccine supply carefully so that vaccines do not expire.

Last reviewed: July 26, 2023

Children and adolescents who have been diagnosed with acute dengue should wait at least 6 months after the date the dengue illness is confirmed to begin the vaccine series.

Last reviewed: January 17, 2025

Both vaccines have been demonstrated to be safe, with side effects typical of those in older age groups. The most common local reaction in this age group is pain at the injection site; the most common systemic symptom in older children was fatigue and in younger children (6 through 23 months) irritability/crying and sleepiness were most common. Fever may occur after either vaccination. Febrile seizures can occur in infants and young children ages 6 months through 5 years as a result of any condition that causes a fever (most common with high fevers). Febrile seizures are uncommon after vaccination. Febrile seizures were rare after mRNA COVID-19 vaccine clinical trials in this age group, and CDC continues to monitor for this adverse event following vaccination in infants and young children.

No cases of myocarditis were reported during the clinical trials for either vaccine. To date, post-authorization surveillance has not detected an increased risk for myocarditis and pericarditis following mRNA COVID-19 vaccination in children ages 6 months–4 years (Pfizer-BioNTech) and ages 6 months–5 years (Moderna).

Last reviewed: November 16, 2024

We are aware that some surgeons advise against vaccination in an arm where lymph nodes were dissected. ACIP does not address this, so feel free to use your professional judgment in determining whether to use the arm that was operated on, the other arm (if not affected), or the anterolateral aspect of the thigh, which is an acceptable secondary route for adult immunization.

Last reviewed: December 28, 2022

Both brands of DTaP-IPV pediatric combination vaccines (Kinrix, GSK; Quadracel, Sanofi) are only licensed for use as the fifth dose of the DTaP vaccine series and the fourth (or fifth, for Quadracel) dose of the IPV series in children age 4 through 6 years. CDC has provided this guidance for when Kinrix or Quadracel are given off-label:

  • Kinrix or Quadracel given to a child younger than 4 years as DTaP and IPV doses 1, 2, or 3: Count as valid if all minimum intervals met.
  • Kinrix or Quadracel given to a child younger than 4 years as DTaP and IPV doses #4 and/or #5: Count as valid for DTaP #4; not valid for DTaP #5 or IPV #4, both of which must be administered at age 4 through 6 years.

However, you should check with your state immunization program to see what they will accept. Checking with your state is particularly important for validating a last dose of IPV vaccine administered before the fourth birthday. Their guidance may vary depending on the date of administration or your upcoming travel plans. Contact information can be found here: www.immunize.org/coordinators.

Last reviewed: July 15, 2023

No. Children with Down syndrome should receive all indicated vaccines on the recommended schedule. These children are often at greater risk for complications from vaccine-preventable diseases than are children without Down syndrome.

Last reviewed: August 29, 2022

The first step is to inform the parent/patient that you administered the wrong vaccine. Next, follow these guidelines:

  • Tdap given to a child younger than age 7 years as either dose 1, 2, or 3, is not valid. Repeat with DTaP as soon as feasible.
  • Tdap given to a child younger than age 7 years as either dose 4 or 5 can be counted as valid for DTaP dose 4 or 5.
  • Tdap or DTaP given to a fully vaccinated child age 7–9 years: the child should receive the routine adolescent Tdap dose at age 11–12 years.
  • Tdap or DTaP given to a fully vaccinated child age 10 years: count this dose as the routine adolescent Tdap dose recommended at age 11–12 years.
  • DTaP given to an undervaccinated child age 7–9 years: count this dose as a Tdap dose of the catch-up series. The child should receive the routine adolescent booster dose of Tdap at age 11–12 years.
  • DTaP given to an undervaccinated child age 10 years: count this dose as the routine adolescent Tdap dose recommended at age 11–12 years.
  • DTaP given to a person age 11 years or older: count this dose as a routine Tdap dose.

Note that DTaP is neither approved nor recommended for people older than 6 years (except hematopoietic stem cell transplant recipients in some situations; see www.cdc.gov/vaccines/hcp/imz-best-practices/altered-immunocompetence.html).

Last reviewed: March 31, 2022

It is not necessary to restart or add doses to the HepB series (or any other routine vaccine series) because of a prolonged interval between doses. Just continue the series from the point where it was interrupted. Note that the 2-dose Recombivax HB series using the adult formulation is approved only for adolescents 11 through 15 years of age. At age 16 years, the schedule reverts to the standard pediatric formulation 3-dose schedule rather than 2 adult doses.

Last reviewed: January 17, 2025

Yes. HPV vaccine should be administered to people who are already sexually active if age appropriate. Routine catch-up vaccination of any person not vaccinated on schedule as a preteen is recommended through age 26 years, and vaccination may be considered with shared clinical decision-making between ages 27 and 45. Ideally, patients should be vaccinated before the onset of sexual activity; however, people who have already been infected with one or more HPV types will still be protected from other HPV types in the vaccine that have not been acquired.

Last reviewed: March 2, 2024

Because she has functional asplenia, she is due for the second dose of the primary series (assuming 8 weeks have passed since the first primary series dose). Because she has a high-risk medical condition she will need periodic booster doses. If she is younger than age 7 years when she receives the second dose of her primary series, she should receive her first booster dose 3 years after completing the primary series. She should then receive a booster dose every five years thereafter. If she is age 7 years or older when she receives the second primary dose she should receive her first booster dose 5 years after the completing the primary series and every five years thereafter.

Last reviewed: November 15, 2024

The vaccine dose (0.2 mL) comes inside a special sprayer device. A plastic clip on the plunger divides the dose into two equal parts. The patient is seated in an upright position with head tilted back. Half of the contents of the sprayer (0.1 mL) is sprayed into each nostril.

Last reviewed: August 11, 2024

CDC currently recommends that people age 50 years or older who have ever received PCV13 and who have also had 1 dose of PPSV23 before turning age 65 should receive either PCV20 or PCV21 at least 5 years after their most recent pneumococcal vaccination.

Last reviewed: November 13, 2024

In August 2024, FDA changed the dosing interval for a 2-dose series of Bexsero (MenB-4C, GSK) from 1 month to 6 months, and recommends that people who receive a second dose of Bexsero less than 6 months after dose 1 receive a third dose at least 6 months after dose 1 and at least 4 months after dose 2. However, no additional primary series doses are recommended for people who previously completed the 2-dose series with the shorter interval, in accordance with the licensed and recommended Bexsero schedule at the time.

In June 2019, ACIP voted to recommend MenB booster doses for people at ongoing increased risk of meningococcal serogroup B disease and the recommendation was published in 2020 (www.cdc.gov/mmwr/volumes/69/rr/pdfs/rr6909a1-H.pdf). As long as you use Bexsero (MenB-4C) as the booster dose, this patient should be given a booster dose of Bexsero now and receive subsequent booster doses every 2–3 years.

The two types of MenB vaccine work differently and are not interchangeable. The only time ACIP recommends restarting the primary series is if the brand used for the primary series is not known or is unavailable.

Last reviewed: November 15, 2024


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Last reviewed: June 22, 2023

Shingrix has been studied in people with certain types of immunocompromise and has been shown to have moderate to high effectiveness against herpes zoster and postherpetic neuralgia. Because the causes of immunocompromise are so varied, the effectiveness and durability of protection provided by Shingrix also may vary depending upon the precise nature and severity of immunocompromise in a given individual.

Last reviewed: March 9, 2022

For children, the first dose should be given at age 12 months with a second dose given at age 4 through 6 years. The second dose could be given earlier, if necessary, as long as there is a 3-month (12-week) interval between doses. Although a 3-month minimum interval is recommended in children younger than age 13, the second dose does not need to be repeated if separated from the first dose by a shorter interval of at least 4 weeks.

All children age 13 years and older as well as adults without evidence of immunity should also have documentation of 2 doses of varicella vaccine, separated by a minimum interval of 4 weeks.

Last reviewed: May 16, 2023

Serologic testing for immunity to hepatitis A virus (HAV) is not necessary after routine HepA vaccination of infants, children or adults. Testing for the presence of anti-HAV antibody one month or more after completing the HepA vaccination series is recommended only for people whose future clinical management depends on knowing their immune status and for whom revaccination might be indicated, such as people living with HIV and other immunocompromised persons (such as transplant recipients and people vaccinated while receiving chemotherapy). In such individuals, if the results of postvaccination testing do not show an adequate immune response (10 mIU/mL or higher), revaccination with a complete series is recommended, followed by a second postvaccination serologic test. If that second test remains negative, no additional vaccination is recommended; however, the patient should be counseled on strategies to avoid exposure to HAV and the need for IG if an exposure occurs. If vaccination results in seroconversion, insufficient data are available to make recommendations concerning repeat testing, booster doses or revaccination.

Last reviewed: June 25, 2023

Dengvaxia is contraindicated for people with a history of immediate hypersensitivity to any vaccine component or a previous dose of this vaccine. A complete list of vaccine components is available in the package insert at www.fda.gov/media/124379/download.

Dengvaxia is a live-attenuated vaccine and also is contraindicated in children with severe immunodeficiency or immunosuppression due to underlying disease or therapy, including children with symptomatic HIV infection or CD4+ T-lymphocyte count of less than 200 per cubic milliliter.

Lack of laboratory evidence of previous dengue infection is also a contraindication to Dengvaxia. www.cdc.gov/vaccines/vpd/dengue/hcp/recommendations.html.

Last reviewed: January 17, 2025

Yes. The DTaP in the Pentacel can be counted. Although Pentacel is licensed as a 4-dose series and this may represent a fifth dose of Pentacel (in which case it would be off-label use), the dose of DTaP counts as the fifth dose of DTaP.

The same principle applies to Vaxelis (DTaP-IPV-Hib-HepB, MCM), which is licensed for use in children ages 6 weeks through 4 years as a 3-dose series of vaccinations routinely recommended at age 2 months, 4 months, and 6 months. The DTaP in a dose of Vaxelis inadvertently administered after the 5th birthday or as the 4th or 5th dose of DTaP (off-label use) may be counted as valid and does not need to be repeated.

Last reviewed: March 31, 2022

Yes. You should draw the blood first and then administer the first dose of vaccine, as transient HBsAg-positivity has been detected after a dose of HepB (see related question).

Last reviewed: January 17, 2025

In recent years, mumps outbreaks have occurred primarily in populations in institutional settings with close contact (such as residential colleges) or in close-knit social groups. The current routine recommendation for 2 doses of MMR vaccine appears to be sufficient for mumps control in the general population, but insufficient for preventing mumps outbreaks in prolonged, close-contact settings, even where coverage with 2 doses of MMR vaccine is high.

In January 2018, the Advisory Committee on Immunization Practices (ACIP) published guidance for MMR vaccination of persons at increased risk for acquiring mumps during an outbreak. Persons previously vaccinated with 2 doses of a mumps virus–containing vaccine who are identified by public health authorities as being part of a group at increased risk for acquiring mumps because of an outbreak should receive a third dose of a mumps virus–containing vaccine to improve protection against mumps disease and related complications. Either brand of MMR vaccine may be used. More information about this recommendation is available at www.cdc.gov/mmwr/volumes/67/wr/pdfs/mm6701a7-H.pdf.

Last reviewed: June 19, 2023

The expiration date is the date by which the vaccine should be used. Vaccines may be used up to and including this date unless otherwise stated in the manufacturer’s product information. The expiration date is based on the assumption that the vaccine has been properly handled and that it has not become contaminated.

Some vaccines expire within a certain time after opening or after reconstitution. Multidose vials that contain bacteriostatic agents that prevent the growth of bacteria and may be used until the expiration date printed on the vial unless they become contaminated. Single-dose vials, COVID-19 vaccine multidose vials, and manufacturer-filled syringes do not contain bacteriostatic agents. Once the cap has been removed or the sterile seal has been broken on these vaccines, they should be administered. Lyophilized (freeze-dried) vaccine must be used within a specified time frame after it has been reconstituted. You may find an educational piece from Immunize.org titled Vaccines with Diluents: How to Use Them helpful. It’s available at www.immunize.org/catg.d/p3040.pdf.

Last reviewed: July 26, 2023

In clinical trials, HPV vaccines were shown to be highly effective (more than 95%) for prevention of HPV vaccine-type infection and disease among people without prior infection with the HPV types included in the vaccine. The most likely explanation for this situation is that the patient was exposed to at least HPV types 16 and 18 prior to vaccination. The HPV vaccine is not effective in preventing infection from HPV types a person has been exposed to prior to vaccination. The vaccine also cannot prevent progression of HPV infection or HPV-related disease. The 9vHPV vaccine protects against 9 different types of HPV.

Last reviewed: March 2, 2024

This situation is not addressed in the ACIP guidelines for meningococcal conjugate vaccine. It is the CDC meningococcal subject matter expert’s opinion that this patient should receive 2 doses of MenACWY separated by at least 8 weeks, followed by a booster dose of MenACWY every 5 years thereafter. The concern is that having had only MPSV4 (Menomune, Sanofi, unavailable since 2017) previously, she may not have an adequate booster response to a single dose of MenACWY.

Last reviewed: November 15, 2024

Yes, unless clinical judgment suggests nasal congestion is present that might keep the vaccine from making good contact with the nasopharyngeal mucosa. In that case, consider either deferring its use until the congestion resolves or using an appropriate alternative influenza vaccine, if available.

Last reviewed: August 11, 2024

Vaccination involves active immunization, where an antigen is administered to a recipient to activate the recipient’s immune system and generate an immune response (which includes developing antibodies). Active immunization may require up to 2 weeks to have its full protective effect, and sometimes a series of vaccinations is required. Protection may last for months or be life-long, depending upon the type of immune response triggered. The effectiveness of a vaccine depends on the recipient’s immune system.

Nirsevimab (Beyfortus, Sanofi) is an injectable, long-acting monoclonal antibody product that gives the recipient direct, immediate protection through passive immunization. The antibodies of nirsevimab circulate in the bloodstream and recognize and attach to the RSV virus if encountered, leading to elimination of the virus. These antibodies protect the patient for at least 5 months until they gradually break down and disappear. The highest risk of severe RSV infection and hospitalization for children is during their first RSV season as an infant. Nirsevimab will not prevent children from getting RSV infections in future seasons, but the general risk of hospitalization due to RSV in childhood is far lower after infancy.

Last reviewed: August 25, 2024

Administer the PCV20. CDC recommendations were updated in October 2024 to state that recipients of PCV13 should receive PCV20 or PCV21 at least one year after the dose of PCV13. CDC no longer recommends PPSV23 as an option following PCV13. PPSV23 is only recommended for adults who receive a dose of PCV15 and have never had a dose of PPSV23 before.

No future doses of any pneumococcal vaccine are currently recommended following a dose of PCV20 or PCV21.

Last reviewed: November 13, 2024

During an outbreak of meningococcal B disease, swift protection of those at risk is prioritized and CDC subject matter experts do not recommend delaying vaccination in order to locate records. Student health services with documentation of MenB vaccination (including brand) of incoming students, either in a state immunization registry or in student health records, will be able to respond most efficiently to an outbreak.

Students whose primary series of MenB vaccine was completed at least 1 year before the outbreak (or as little as 6 months before the outbreak, if recommended by public health) should receive a single booster dose of the same brand of MenB vaccine. If the same brand is unavailable, they should restart the primary series with the available brand. If the brand of the primary series is unknown, administer a dose of the available product and counsel the recipient to request records of the primary series: if the primary series brand is different, then in order to ensure optimal protection, the recipient should be given a booster dose of the primary series product a minimum of 4 weeks after the most recent MenB dose, or they should complete a new 3-dose primary series with the available product for accelerated protection.

Last reviewed: November 15, 2024

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