Ask the Experts: All Questions

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Results (1374)

ACIP recommends that people capable of bearing children be asked if they are currently pregnant or attempting to become pregnant. Vaccination should be deferred for those who answer “yes.” Those who answer “no” should be advised to avoid pregnancy for 4 weeks following vaccination. Pregnancy testing is not necessary.

Last reviewed: June 19, 2023

Serologic testing for immunity after HepB vaccination is recommended only for people whose subsequent clinical management depends on knowledge of their immune status. Testing is not necessary after routine vaccination of adults.

Post-vaccination anti-HBs testing of certain adults is recommended for the following reasons:

  • To determine the need for revaccination and the type of follow-up testing:
    • HCP and public safety workers at risk for blood or body fluid exposure
    • Hemodialysis patients (and others who might require outpatient hemodialysis)
    • People with HIV, and other immunocompromised people (e.g., hematopoietic stem-cell transplant recipients or people receiving chemotherapy)
  • To determine the need for revaccination and for other methods of protection against HBV infection:
    • Sex partners or needle-sharing partners of HBsAg-positive people

Testing should be performed 1 to 2 months after the last dose of vaccine.

Last reviewed: January 17, 2025

The CDC zoster subject matter experts recommend that in this situation you should wait 4 weeks before giving a repeat dose.

Last reviewed: December 28, 2022

No. Tdap is an inactivated vaccine and may be administered at the same time as Rhogam (in a separate site with a separate syringe).

Last reviewed: March 31, 2022

No. Just give the final dose of HepA vaccine prior to travel.

Last reviewed: June 25, 2023

Every year more healthcare facilities are adopting mandatory vaccination policies for their employees. Immunize.org has included more than 1,200 of these on its Honor Roll for Patient Safety, which gives special recognition to institutions that enforce mandatory vaccination for all personnel who are in the vicinity of a patient (including volunteers and housekeeping staff). To read more about the Honor Roll, or to apply for recognition, go to www.immunize.org/about/excellence/honor-rolls/influenza-vaccination/. In addition, the National Adult and Influenza Immunization Summit (NAIIS) has developed tools to assist post-acute and long-term care facilities that plan to implement influenza vaccination requirements for HCP at www.izsummitpartners.org/naiis-workgroups/influenza-workgroup/tools-for-ltcf/. We hope reviewing these policies and tools will give you the information you need to assist in developing an effective policy for your facility.

Last reviewed: August 11, 2024

Your patient may choose to receive the vaccines at the same visit or separately, without regard to the timing interval. In general, when deciding whether to coadminister other vaccines with COVID-19 vaccine, you should consider whether the patient is behind or at risk of becoming behind on recommended vaccines, their risk of vaccine-preventable disease (e.g., during an outbreak or occupational exposures), and the reactogenicity profile of the vaccines.

When multiple vaccines are administered at a single visit, administer each injection in a different syringe and at a different injection site. For adolescents and adults, the deltoid muscle may be used for more than one injection, though injection sites should be at least one inch apart. It is generally preferable to administer reactogenic vaccines such as Shingrix and COVID-19 vaccine in different arms, if possible. If the patient prefers both injections in the same deltoid, that is also acceptable.

Immunize.org has developed a one-page guide to administering multiple intramuscular vaccinations to an adult at one visit: www.immunize.org/catg.d/p2030.pdf.

Last reviewed: November 16, 2024

Based on changes to the ACIP recommendations made in October 2024, a second dose of PPSV23 is no longer recommended for any adult. Adults age 19 through 49 years with immunocompromising conditions who received a dose of PCV15 followed by a dose of PPSV23 have received a complete pneumococcal vaccine schedule, and no further doses are recommended. If they received PCV13 and PPSV23, instead of PCV15, CDC recommends a dose of PCV20 or PCV21 should be given 5 years after the first dose of PPSV23, if the patient has have one of the following immunocompromising conditions: 

  • Kidney disease and on maintenance dialysis
  • Kidney disease with nephrotic syndrome
  • Asplenia or splenic dysfunction
  • Congenital or acquired immunodeficiency, including B-(humoral) or T-lymphocyte deficiency; complement deficiencies, particularly C1, C2, C3, and C4 deficiency; and phagocytic disorders (excluding chronic granulomatous disease)
  • Treatment with immunosuppressive drugs or radiation therapy (including treatment for Hodgkin disease, leukemias, lymphomas, malignant neoplasm, and solid organ transplant)
  • HIV infection
  • Sickle cell disease or other hemoglobinopathies
Last reviewed: November 13, 2024

No. Seasonal influenza vaccines are reformulated each year; for this reason, all unused seasonal influenza vaccines expire and should be discarded no later than the end of June each season. RSV products (vaccines and preventive antibody) do not change each season and products in your storage unit now may not expire until sometime during or after the next season.

Unless state or territorial public health authorities advise otherwise based upon local conditions, RSV vaccine should not be given during pregnancy after January. Likewise, nirsevimab (Beyfortus, Sanofi) should not be given to infants after March or before October unless specifically instructed by public health authorities.

Vaccination of eligible adults age 60 years or older will have the most benefit if RSV vaccine is administered in late summer or early fall, just before the typical RSV season. However, eligible adults may be vaccinated at any time of year if there is a need to vaccinate at other times of year. Vaccination is expected to provide meaningful protection from serious RSV disease for 2 years or longer. Only one dose of RSV vaccine is recommended: revaccination is not recommended.

Properly store and clearly label unexpired products remaining in your storage unit during periods when they are not in use and train staff on the timing of these products, especially for vaccination during pregnancy and use of nirsevimab. Consider storage and labeling that minimizes the risk of mishandling or administration outside the times when the product is recommended to be used.

Last reviewed: August 25, 2024


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Last reviewed: June 7, 2024

Sexually transmitted infections, including hepatitis B, can be transmitted by sexual assault. Unless the victim has a documented history of completed HepB vaccination, a series of HepB alone (2 or 3 doses depending on brand) should be administered with the first dose as soon as possible after the assault. Administration of hepatitis B immune globulin (HBIG) is not necessary.

Last reviewed: January 17, 2025

Any Shingrix, either antigen or diluent, that is exposed to freezing temperature should not be used. If a dose exposed to freezing temperature is given to a patient the dose should be considered invalid and should be repeated 4 weeks after the invalid dose.

Last reviewed: March 9, 2022

Though vaccination is the most effective means of protecting your patients from influenza, there may be instances where employees are not vaccinated for medical or personal reasons. In these instances, you may want to consider reassigning unvaccinated workers to non-patient areas or requiring that they wear masks throughout the influenza season.

Last reviewed: August 11, 2024

Vaccine may lose potency rapidly if not stored according to the manufacturer’s instructions. However, it may still be permissible to use vaccine that has not been properly stored. Put the affected vaccine vials into the freezer after you have marked them so they are not confused with the unaffected vials, then call the manufacturer at 1-800-9-VARIVAX (1-800-982-7482) for further guidance about whether the vaccine is still usable. Unreconstituted varicella vaccine may be stored in the refrigerator for up to 72 hours before use. If refrigerated varicella vaccine is not used within 72 hours, it should be discarded.

If you have inadvertently left your vaccine at room temperature instead of in the freezer or have experienced a power failure, label the affected vaccine to keep it separated from unaffected vaccine and return it to recommended storage conditions in a freezer promptly, then contact the manufacturer for further guidance. Do not administer the vaccine until you have consulted with Merck.

Last reviewed: May 16, 2023

Any RZV, either antigen or diluent, that is exposed to freezing temperature should not be used. If a dose exposed to freezing temperature is given to a patient the dose should be considered invalid and should be repeated 4 weeks after the invalid dose.

Last reviewed: December 28, 2022

Children, age 7 years and older, and adults who have never received tetanus-containing vaccines, or whose vaccination history is unknown, should receive the 3-dose series. In this situation, ACIP recommends Tdap for dose #1, followed 4 weeks later by Td or Tdap for dose #2, followed at least 6 months later by Td or Tdap for dose #3. The amount of protection provided by one or more doses of Tdap in a person who has not previously received pertussis vaccine is not known. Following the primary series, booster doses of Td or Tdap should be given every 10 years thereafter.

Last reviewed: March 31, 2022

Possibly. Since IG protects against hepatitis A infection for only 1 to 2 months, depending on the dosage given, additional IG may be needed if the infant is not yet age 6 months. Once the child has reached six months of age, HepA vaccine should be given.

Last reviewed: June 25, 2023

No specific action needs to be taken other than to reassure the pregnant person that no adverse outcomes are expected as a result of this vaccination. MMR vaccination during pregnancy is not a reason to terminate the pregnancy. You should consult with others in your healthcare setting to identify ways to prevent such vaccination errors in the future. Detailed information about MMR vaccination in pregnancy is included in the 2013 MMR ACIP statement, available at www.cdc.gov/mmwr/pdf/rr/rr6204.pdf.

Last reviewed: June 19, 2023

They need a dose of PCV20 or PCV21, but not another dose of PPSV23. CDC recommends that people age 50 or older who received PCV13 and either one or two doses of PPSV23 before age 65 should receive a dose of PCV20 or PCV21 at least 5 years after the last pneumococcal vaccine dose. If they received PCV15 followed by PPSV23, they are not recommended to receive any additional pneumococcal vaccine doses at this time.  

A patient age 50 or older who received one or two doses of PPSV23 earlier in life but has not received any PCV product, or their history of PCV vaccination is only PCV7 or unknown, is recommended to receive a single dose of a currently recommended pneumococcal conjugate vaccine (PCV15, PCV20, or PCV21) at least one year after the last dose of PPSV23. 

Last reviewed: November 13, 2024

Neither the Advisory Committee on Immunization Practices (ACIP) nor the manufacturers address the timing of vaccination and dialysis. People with end-stage renal disease including predialysis, hemodialysis, peritoneal dialysis, and home dialysis should be tested for hepatitis B surface antibody (anti-HBs) 1–2 months after vaccination, and annually. If the anti-HBs level is below 10mIU/mL, they should be revaccinated.

Last reviewed: January 17, 2025

Both lyophilized Shingrix and the adjuvant solution diluent must be stored at refrigerator temperature, between 2° and 8°C (between 36° and 46°F). Protect the vials from light. Do not freeze. Vaccine or adjuvant solution that has been frozen must be discarded. If vaccine that was frozen was administered, the dose does not count and should be repeated. The repeat dose should be administered 4 weeks after the frozen dose. After reconstitution, administer Shingrix immediately or store refrigerated between 2° and 8°C (between 36° and 46°F) and use within 6 hours. Discard reconstituted vaccine if not used within 6 hours.

Last reviewed: March 9, 2022

No. ACIP recommends that anyone capable of bearing children be asked if they are currently pregnant or attempting to become pregnant. Vaccination should be deferred for those who answer “yes.” Those who answer “no” should be advised to avoid pregnancy for one month following vaccination.

Last reviewed: June 19, 2023

Yes. ACIP recommends that all children age 1 year through 18 years should be vaccinated against hepatitis A. VFC HepA vaccine may be administered to any eligible child, including those recommended for vaccination at 6 through 11 months of age as a result of travel to an HAV-endemic area.

Last reviewed: June 25, 2023

The fourth dose of DTaP may be given as early as age 12 months if at least 6 months have passed since the third dose.

Last reviewed: March 31, 2022

The timing of CDC-recommended vaccination is unaffected by the receipt of COVID-19 monoclonal antibodies or convalescent plasma.

Last reviewed: November 16, 2024

The vaccine manufacturer does not recommend transporting varicella-containing vaccines (varicella, MMRV). If these vaccines must be transported (for example during an emergency), CDC recommends use of a portable vaccine freezer unit or qualified container and packout that maintains temperatures between -50°C and -15°C (- 8°F and +5°F). Do not use dry ice, even for temporary storage. Dry ice might expose the vaccines to temperatures colder than -50°C (-58°F), resulting in compromise of the vial stopper material.

Follow these steps for transporting frozen vaccines:

  • Place a temperature monitoring device (preferably with a buffered probe) in the container as close as possible to the vaccines.
  • Immediately upon arrival at the destination, unpack the vaccines and place them in a freezer at a temperature range between -50°C and -15°C (-58°F and +5°F). Any stand-alone freezer or freezer purpose built for vaccine storage that maintains these temperatures is acceptable.
  • Record the time vaccines are removed from the storage unit and placed in the transport container, the temperature during transport, and the time at the end of transport when vaccines are placed in a stable storage unit.

If necessary, varicella-containing vaccines may be transported or stored at refrigerator temperature between 2°C and 8°C (between 36°F and 46°F) for up to 72 continuous hours prior to reconstitution. To do so, follow the steps above using a portable vaccine refrigerator unit or a qualified container and packout designed to maintain vaccine storage temperatures between 2°C and 8°C (between 36°F and 46°F).

Transport of varicella-containing vaccine at temperatures other than the recommended range between -50°C and -15°C (-58°F and +5°F) is considered a temperature excursion, so contact Merck at (800) 982-7482 for further guidance. Do not discard vaccines without contacting the manufacturer and/or your immunization program for guidance.

For additional guidance, see the CDC Vaccine Storage and Handling Toolkit at www.cdc.gov/vaccines/hcp/admin/storage/toolkit/storage-handling-toolkit.pdf.

Last reviewed: May 16, 2023

If a vaccine is covered under the National Childhood Vaccine Injury Act, as influenza vaccine is, it is mandatory under federal law to give the VIS for that vaccine to the vaccinee, regardless of age. Therefore, when you give influenza vaccine to employees and staff, you are required by law to provide them with a VIS.

The inactivated and recombinant influenza vaccine VIS and all available translations of it are here: www.immunize.org/vaccines/vis/influenza-inactivated/. The live attenuated influenza (LAIV) VIS and all available translations of it are here: www.immunize.org/vaccines/vis/influenza-live/.

Immunize.org also offers a printable PDF document with QR codes for easy access to all translations of the inactivated and recombinant influenza vaccine VIS: www.immunize.org/wp-content/uploads/catg.d/p2092.pdf. Healthcare providers or recipients can scan the QR codes to access a digital copy of the English version or one of many translations on their mobile device.

Last reviewed: August 11, 2024

No. This patient should receive a dose of PCV15, PCV20, or PCV21 now. As of October 2024, CDC does not recommend revaccination with PPSV23 for any adult who has received a dose of PPSV23.

Last reviewed: November 13, 2024

Recommendations for immunocompromised people, such as hemodialysis patients, are different than those for immunocompetent people. Hemodialysis patients who do not respond to an initial vaccine series should be revaccinated with two to four additional doses of HepB (depending on the brand). Hemodialysis patients are considered immune as long as they have adequate anti-HBs (at least 10 mIU/mL). For hemodialysis patients who have responded with adequate anti-HBs (postvaccination testing should be done 1 to 2 months after the vaccine series) to HepB vaccination, no HBsAg testing is needed but anti-HBs should be done annually. If anti-HBs declines below 10 mIU/mL, a booster dose of HepB should be given and annual anti-HBs testing should be continued. Retesting immediately after the booster dose is not necessary.

Last reviewed: January 17, 2025

Yes. According to the manufacturer, unreconstituted varicella vaccine may be stored at refrigerator temperature (2°C to 8°C, 36°F to 46°F) for up to 72 continuous hours prior to reconstitution. Vaccine stored at 2°C to 8°C that is not used within 72 hours of removal from -15°C (+5°F) storage should be discarded. See www.merck.com/product/usa/pi_circulars/v/varivax/varivax_pi.pdf.

Last reviewed: May 16, 2023

Some studies have shown an increase in HCP influenza vaccine acceptance when decliners are required to sign such a statement. In addition, such statements can help a vaccination program assess the reasons for declination and plan future educational efforts. Immunize.org has posted the following suggested declination form for healthcare workers at www.immunize.org/catg.d/p4068.pdf.

Last reviewed: August 11, 2024

Yes. Measles, mumps, and rubella vaccine viruses are not transmitted from the vaccinated person, so MMR vaccination of a household contact does not pose a risk to a pregnant household member.

Last reviewed: June 19, 2023

You should try to achieve at least 4 total doses. Give additional doses of DTaP with 4-week intervals until you achieve 3 total doses. Then, if 6 months pass and the child has not turned seven years old, give the 4th dose of DTaP: if the child has turned seven years old, you may administer a dose of Tdap vaccine at that time.

Last reviewed: March 31, 2022

It depends on whether that person has a history of HAV infection. Unless there are medical records that document prior HAV infection, serologic testing for immunity (positive test for total anti-HAV) is the only way to determine if vaccination is necessary. For people from countries with high rates of HAV infection, such as Vietnam and Mexico, serologic testing might be done to prevent unnecessary vaccination. The cost effectiveness of serologic testing, however, should be balanced against the possibility of delaying needed vaccination while awaiting test results.

Last reviewed: June 25, 2023

Shingrix is stored at refrigerator temperature. Transport of refrigerated vaccines is described in detail in the CDC Storage and Handling Toolkit, available at www.cdc.gov/vaccines/hcp/admin/storage/toolkit/storage-handling-toolkit.pdf, pages 22–24. Providers should also review the vaccine package inserts for the specific vaccines being transported.

Last reviewed: March 9, 2022

Yes. There are more than 100 known serotypes of pneumococcus. Infection with one serotype does not necessarily produce immunity to other serotypes. As a result, if the person is a candidate for vaccination, they should receive it even after one or more episodes of pneumococcal disease.

Last reviewed: November 13, 2024

There is no maximum number of HepB booster doses a dialysis patient can receive. Serology should be performed once a year and a booster dose given if serology is negative (less than 10 mIU/mL). Serology is not recommended more frequently than once a year, so boosters wouldn’t be given more than once a year.

Last reviewed: January 17, 2025

Influenza virus is easily spread from healthcare workers to their patients, and infection usually leads to clinical illness. Pneumococcus is probably not spread from healthcare workers to their patients as easily as is influenza, and infection with pneumococcus does not necessarily lead to clinical illness. Host factors (such as age, underlying illness) are more important in the development of invasive pneumococcal disease than nasopharyngeal colonization with the organism.

Last reviewed: November 13, 2024

No, as long as there are medical records that document that the person was previously infected with HAV (i.e., positive test for total anti-HAV). If there is any doubt that the person actually was infected with HAV, HepA vaccine and/or IG should be given. The vaccine or IG will not harm a person who is already immune.

Last reviewed: June 25, 2023

Although the child would be considered complete for tetanus and diphtheria toxoids, she is not complete for pertussis vaccine. DTaP vaccines are FDA-approved only through age 6 years so no more DTaP doses are recommended.

However, ACIP recommends that children age 7–10 years who are not fully vaccinated against pertussis (defined as 5 doses of DTaP or 4 doses of DTaP if the fourth dose was administered on or after the fourth birthday) and who do not have a contraindication to pertussis vaccine should receive a single dose of Tdap to provide protection against pertussis. If the child in this case is age 7–9 years at the time of Tdap vaccination, the next dose due will be the routine adolescent dose of Tdap at age 11 or 12 years. If the child is age 10, the dose counts as the adolescent dose and no additional dose at age 11 or 12 years is recommended.

Last reviewed: March 31, 2022

In 2013, ACIP updated its recommendation for this situation (see www.cdc.gov/mmwr/pdf/rr/rr6204.pdf, pages 18–20). It is recommended that people capable of bearing children who have received 1 or 2 doses of rubella-containing vaccine and have rubella serum IgG levels that are not clearly positive should be administered 1 additional dose of MMR vaccine (maximum of 3 doses) and do not need to be retested for serologic evidence of rubella immunity. MMR should not be administered to a pregnant person.

Last reviewed: June 19, 2023

There are many professional associations that have issued policy position statements supporting mandatory healthcare worker influenza vaccination. You can find information about these organizations and their position statements at Immunize.org’s Influenza Vaccination Honor Roll web page: www.immunize.org/about/excellence/honor-rolls/influenza-vaccination/.

Last reviewed: August 11, 2024

Contraindications to egg-based inactivated influenza vaccines (IIV) are a severe allergic reaction to a prior dose of any influenza vaccine (any egg-based IIV, ccIIV, RIV, or LAIV of any valency) or a severe allergy to an influenza vaccine component (except egg). ACIP recommends that people with egg allergy of any severity may receive any influenza vaccine appropriate for their age and health status.

Precautions to egg-based IIV include moderate or severe acute illness, and history of Guillain-Barré syndrome within 6 weeks after a dose of influenza vaccine.

Contraindications to cell culture-based IIV (ccIIV) are a history of a severe allergic reaction to a previous dose of ccIIV or any component of ccIIV.

Precautions to ccIIV are moderate or severe acute illness, a history of Guillain-Barré syndrome within 6 weeks after a dose of any influenza vaccine, and a history of a severe allergic reaction to a previous dose of another type of influenza vaccine (e.g., any egg-based IIV, RIV, or LAIV).

Contraindications to RIV are a history of a severe allergic reaction to a previous dose of RIV or any component of RIV.

Precautions to RIV are moderate or severe acute illness, a history of Guillain-Barré syndrome within 6 weeks after a dose of any influenza vaccine, and a history of a severe allergic reaction to a previous dose of another type of influenza vaccine (e.g., any egg-based IIV, ccIIV, or LAIV).

Last reviewed: August 11, 2024

ACIP recommends that vaccinated people of childbearing age who have received one or two doses of rubella-containing vaccine and have a rubella serum IgG levels that is not clearly positive should be administered one additional dose of MMR vaccine (maximum of three doses). Repeat serologic testing for evidence of rubella immunity is not recommended. See www.cdc.gov/mmwr/pdf/rr/rr6204.pdf, pages 18–20, for more information on this issue.

MMR vaccines should not be administered to people known to be pregnant or attempting to become pregnant. Because of the theoretical risk to the fetus when the mother receives a live virus vaccine, people capable of bearing children should be counseled to avoid becoming pregnant for 28 days after receipt of MMR vaccine.

Last reviewed: June 19, 2023

No serious adverse events have been attributed definitively to HepA vaccine. Among adults, the most frequently reported side effects are soreness at the site of the injection and headache. In children, the most frequently reported side effect is soreness at the injection site. The frequency of side effects after administration of Twinrix is similar to those reported when the two single-antigen vaccines were administered.

Last reviewed: June 25, 2023

If DTaP #4 is given with at least a 4-month interval after DTaP #3, it does not need to be repeated. The minimum age of 12 months for the fourth dose must be met. Decreasing the interval to less than 6 months, however, is not recommended.

Last reviewed: March 31, 2022

A severe allergic reaction to any influenza vaccine is a contraindication to receiving additional doses of the same vaccine or receiving any egg-based influenza vaccines. The following table summarizes the contraindications and precautions for different types of influenza vaccine and has been adapted from table 3 of the 2022-23 influenza ACIP recommendations at www.cdc.gov/mmwr/volumes/71/rr/pdfs/rr7101a1-H.pdf. No changes to this general guidance were made for 2024-25 influenza season products.

Vaccine (of any valency) associated with previous serious or anaphylactic reaction Available 2024-25 influenza vaccines
Egg-based IIVs
and LAIV		 Cell-culture- based IIV: ccIIV (Flucelvax) Recombinant IIV: RIV (Flublok)
Any egg-based IIV or LAIV Contraindication Precaution † Precaution †
Any ccIIV Contraindication Contraindication Precaution †
Any RIV Contraindication Precaution † Contraindication
Unknown influenza vaccine Allergist consultation recommended

† Note regarding patients having either of the above precautions for either ccIIV or IIV: use of ccIIV and RIV in such instances should occur in an inpatient or outpatient medical setting under the supervision of a healthcare provider (HCP) who can recognize and manage severe allergic reaction; HCPs can also consider consulting with an allergist to help identify the vaccine component responsible for the reaction.

Last reviewed: August 11, 2024

PCV vaccines are conjugated to a type of diphtheria toxoid. If someone has a history of anaphylaxis following diphtheria-containing vaccine, it might be due to the diphtheria toxoid, and the cause of the anaphylactic allergy should be identified before the administration of a PCV vaccine. This could be difficult since no single-antigen diphtheria toxoid is available in the U.S. Fortunately, true anaphylactic allergy to diphtheria-containing vaccine is rare.

Last reviewed: November 13, 2024

Yes, they may be vaccinated with any FDA-licensed or FDA-authorized COVID-19 vaccine (Moderna, Pfizer-BioNTech, or Novavax) as long as they do not have a contraindication to vaccination. Antibody testing is not recommended to assess for immunity to SARS-CoV-2 following COVID-19 vaccination.

Recipients should be counseled about the unknown and variable effectiveness of COVID-19 vaccination in immunocompromised populations and the potential for reduced immune responses. They may consider other practices to reduce their risk of infection. CDC has published additional information about respiratory virus prevention for people with weakened immune systems: www.cdc.gov/respiratory-viruses/risk-factors/weakened-immune-systems.html.

CDC provides detailed considerations for vaccination and the use of pemivibart (Pemgarda, Invyvid) long-acting monoclonal antibody for pre-exposure prophylaxis in people with moderate or severe immunocompromise here: www.cdc.gov/vaccines/covid-19/clinical-considerations/interim-considerations-us.html#immunocompromised.

Last reviewed: November 16, 2024

Yes. If given on the same day as separate injections in separate sites, two injections of Engerix-B 20 mcg can be counted as the equivalent of one Recombivax HB 40-mcg dose. According to the package insert, Engerix-B is licensed for use in this manner (vaccine package inserts for all vaccines are available at www.immunize.org/fda). Note that an all-Engerix-B or mixed-brand dialysis schedule is a 4-dose series (doses at 0, 1, 2, and 6 months). Vaccination using only Recombivax HB dialysis formulation is a 3-dose schedule (doses at 0, 1, and 6 months). Heplisav-B has not been evaluated for use in dialysis patients.

Last reviewed: January 17, 2025

Hepatitis A vaccine is contraindicated for people with a history of a severe allergic reaction to a previous dose of HepA vaccine or to a vaccine component. As with all other vaccines, there is a precaution when giving it to anyone who is moderately or severely ill.

Last reviewed: June 25, 2023

MMR can be administered any time after delivery. The vaccine should be administered to a post-partum mother who is susceptible to either measles, mumps, or rubella before hospital discharge, even if the mother has received RhoGam during the hospital stay, leaves in less than 24 hours, or is breastfeeding.

Last reviewed: June 19, 2023

In general, a child should receive no more than four doses of DTaP before 4 years of age (preferably by 2 years of age). The ACIP recommends that a dose of DTaP be given at 4–6 years of age. Many states have school immunization laws which also require at least one dose of DTP/DTaP on or after the fourth birthday. This dose is important to boost immunity to pertussis.

Last reviewed: March 31, 2022

Contraindications are:

  • a history of severe allergic reaction to a vaccine component (except egg) or after a previous dose of any influenza vaccine (people with egg allergy of any severity may receive LAIV if it is otherwise appropriate for their age and health status)
  • concomitant aspirin- or salicylate-containing therapy in children and adolescents because of the risk of Reye syndrome
  • children age 2 through 4 years who have received a diagnosis of asthma or whose parents or caregivers report that a healthcare provider has told them during the preceding 12 months that their child had wheezing or asthma or whose medical record indicates a wheezing episode during the preceding 12 months
  • immunosuppression due to any cause, including medications, congenital or acquired immunodeficiency states, HIV infection, anatomic asplenia or functional asplenia (e.g., due to sickle cell anemia)
  • cranial cerebral spinal fluid (CSF) leak or cochlear implant (due to potential for CSF leak)
  • close contacts and caregivers of severely immunosuppressed people who require a protected environment
  • pregnancy
  • receipt of influenza antiviral medication within the previous 48 hours (for oseltamivir or zanamivir), previous 5 days (for peramivir), or previous 17 days (for baloxavir)

Precautions are:

  • moderate or severe acute illness with or without fever (defer)
  • history of Guillain-Barré syndrome within 6 weeks after a dose of influenza vaccine
  • asthma in a person age 5 years or older
  • underlying medical conditions that might predispose to complications after influenza virus infection, such as chronic pulmonary, cardiovascular (except isolated hypertension), renal, hepatic, neurologic, hematologic, or metabolic disorders (including diabetes mellitus)
Last reviewed: August 11, 2024

Anaphylaxis occurs at a rate of approximately 5 cases per 1 million mRNA COVID-19 vaccinations administered. History of an anaphylactic reaction to a dose of mRNA COVID-19 vaccine is a contraindication to receipt of further doses of mRNA-type COVID-19 vaccines. However, a person with a contraindication to one type of COVID-19 vaccine (mRNA) may receive the alternative COVID-19 vaccine type (in this case, the adjuvanted protein subunit vaccine by Novavax) in the usual vaccination setting. CDC encourages consultation with an allergist-immunologist to provide expert evaluation of the original allergic reaction, and depending on the outcome of that evaluation, reassess whether administration of additional doses of the original vaccine type may be possible.

Last reviewed: November 16, 2024

If you stock PCV15 and plan to use the PCV15 and PPSV23 combined series to vaccinate patients for whom this is an option, you should always give the PCV15 first. PCV is always recommended to be given before PPSV23, based on studies demonstrating a better immune response to serotypes contained in both vaccines when the conjugate vaccine is given first. These vaccines should not be given at the same visit.

The routine interval between PCV15 and PPSV23 is one year; however, PPSV23 may be administered a minimum of 8 weeks after PCV15 when the recipient has an immunocompromising condition, cochlear implant, or cerebrospinal fluid leak. If PPSV23 is inadvertently administered first, wait a minimum of one year to administer PCV15, PCV20, or PCV21, because there is evidence that the immune response to serotypes contained in the PCV is diminished when PCV is administered soon after PPSV23.

Last reviewed: November 13, 2024

When using Engerix-B or Recombivax HB brands of HepB to vaccinate hemodialysis or other immunocompromised people, a higher dose is recommended, so to the extent these patients are immunocompromised, this is within ACIP recommendations (note that “immunocompromised” is not defined in the recommendations). Regardless, this practice is appropriate for several reasons, including that these patients may be starting hemodialysis soon, and because use of the higher dose is not harmful. This is somewhat of a gray area but the clinician can use clinical judgment. Heplisav-B has not been evaluated for use in dialysis or pre-dialysis patients.

Last reviewed: January 17, 2025

No. This issue has been studied extensively, including a thorough review by the independent Institute of Medicine (IOM). The IOM issued a report in 2004 that concluded there is no evidence supporting an association between MMR vaccine or thimerosal-containing vaccines and the development of autism. For more information on thimerosal and vaccines in general, visit www.cdc.gov/vaccine-safety/about/thimerosal.html.

Last reviewed: June 19, 2023

Yes. ACIP recommends that pregnant women at risk for HAV infection during pregnancy or at risk for a severe outcome from HAV infection should be vaccinated during pregnancy if not previously vaccinated. Pregnant women should be vaccinated for the same indications as non-pregnant women. For additional details, see page 20 of the current ACIP recommendations: www.cdc.gov/mmwr/volumes/69/rr/pdfs/rr6905a1-H.pdf.

Last reviewed: June 25, 2023

ACIP and AAP both recommend that children receive no more than 6 doses of diphtheria and tetanus toxoids (e.g., DT, DTaP, DTP) before the seventh birthday because of concern about adverse reactions, primarily local reactions. Half doses of DTaP are also not recommended under any circumstances, and should not be counted as part of the vaccination series. Only documented doses (i.e., those recorded in an electronic or written record) count toward the maximum of 6 doses.

Last reviewed: March 31, 2022

This condition is not rare and is sometimes referred to as “COVID arm”. Future doses should be given as recommended. Individuals with only a delayed-onset local reaction (e.g., redness, induration, itching) around the injection site area after an mRNA vaccine dose do not have a contraindication or precaution to subsequent doses. Consider administering the next dose in the opposite arm, if possible.

These delayed-onset local reactions are sometimes quite large but are self-limited. It is not known whether individuals who experienced a delayed-onset injection site reaction after one dose will experience a similar reaction after future doses. These reactions are not believed to represent an increased risk for anaphylaxis after future doses.

Patients who experience “COVID arm” may take an antihistamine if it is itchy or a pain medication, such as acetaminophen or a non-steroidal anti-inflammatory (NSAID), if it is painful.

Last reviewed: November 16, 2024

Everyone age 6 months of age or older with egg allergy and no contraindication to vaccination should receive an influenza vaccine. Any influenza vaccine (egg based or non-egg based) appropriate for the person’s age and health status can be used.

Egg allergy alone does not require any additional safety measures for influenza vaccination beyond those recommended for any recipient of any vaccine. As a general principle, all vaccines should be administered in settings in which personnel and equipment needed for rapid recognition and treatment of acute hypersensitivity reactions are available.

For more on the evidence and rationale supporting ACIP’s recommendations regarding influenza vaccination and egg allergy, see pages 12 and 13 of the ACIP recommendations for the 2023–24 season at www.cdc.gov/mmwr/volumes/72/rr/pdfs/rr7202a1-H.pdf.

Last reviewed: August 11, 2024

PCV15 and PPSV23 vaccines should not be given at the same visit. When administering PCV15 followed by PPSV23, give PCV15 first followed by PPSV23 one year later. Providers can consider waiting a minimum interval of 8 weeks to give PPSV23 to people with immunocompromising conditions, cochlear implant, or cerebrospinal fluid (CSF) leak.

If a patient inadvertently received PPSV23 before PCV15, a minimum interval of at least 1 year between doses is recommended and a shorter interval is not recommended.

Last reviewed: November 13, 2024

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