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.
No, but the PPSV23 will render the PCV15 dose less immunogenic. In this scenario, the best schedule is to give a MenACWY vaccination (any brand) simultaneously with either PCV15 or PCV20. If PCV20 is given, no additional pneumococcal vaccine doses are recommended. If PCV15 is given, then PPSV23 should be given at least eight weeks later. ACIP recommends giving PCV before PPSV23 in order to maximize the immune response to PCV. PPSV23 may blunt the immune response to the serotypes contained in PCV if PCV is given after PPSV23, although in children there is a smaller effect than in adults. PCV21 (Capvaxive, Merck) is not an option because it is not licensed or recommended for use in children. Note that a 10-year-old child with persistent complement component deficiency should also be vaccinated against meningococcal B disease.
Low-dead-space syringes can reduce vaccine wastage. In 2026–27 only a small quantity of Fluzone (Sanofi) is available in a 5.0 mL multidose vial. Follow the manufacturer’s package insert for the number of doses that may be withdrawn.
There is an extremely rare risk of myocarditis (inflammation of the heart muscle) and/or pericarditis (inflammation of the tissue surrounding the heart) following receipt of any COVID-19 vaccine. This rare risk is greatest in biological males age 12 through 39 years. The balance of benefit and risk depends on age, sex, underlying conditions, prior infection and vaccination, and the vaccine schedule. COVID-19 itself is more likely to cause myocarditis and other cardiac complications.
The risk after vaccination appears related to age (12 through 39 years), biological sex (male), and the short (3- to 4-week) interval between initial series doses. Under CDC’s 2026–2027 schedule, an initial series is not recommended except in infants and toddlers younger than age 2 years or in people with moderate or severe immunocompromise. CDC states that extending the interval between the first and second doses to 8 weeks in children age 6 through 23 months who are not moderately or severely immunocompromised might reduce the extremely rare risk of myocarditis following the second dose in this age group; however, this is not recommended if delaying vaccination poses an unacceptable risk of severe COVID-19 illness.
Most patients diagnosed with myocarditis after mRNA COVID-19 vaccination have been hospitalized for short periods, with most experiencing resolution of acute symptoms by hospital discharge. CDC continues to assess long-term outcomes in people with myocarditis after mRNA COVID-19 vaccination.
CDC recommends that people who receive COVID-19 vaccines, especially males age 12 through 39, be counseled about the risk of myocarditis or pericarditis and advised to seek medical attention promptly if they develop chest pain, shortness of breath, or feelings of a fast, fluttering, or pounding heartbeat.
Cases of myocarditis and pericarditis were identified in clinical trials of the adjuvanted protein subunit COVID-19 vaccine (now with brand-name Nuvaxovid) and have also been reported during post-authorization use outside the United States.
CDC’s complete interim clinical considerations for COVID-19 vaccination and myocarditis or pericarditis are available here: www.cdc.gov/covid/hcp/vaccine-considerations/safety-considerations.html.
Anti-HBs testing for HCP who receive both hepatitis B immune globulin (HBIG) and hepatitis B vaccine can be conducted as soon as 6 months after receipt of the HBIG.
Children age 7–10 years should receive Tdap if they are not fully vaccinated for prevention of pertussis. Otherwise they may receive Td or Tdap. If additional doses are necessary for full tetanus protection, they may be administered as Td or Tdap. Adolescents, and adults age 11 years and older should receive a single dose of Tdap, if they have not received a dose of Tdap after the 11th birthday, otherwise they may receive Td or Tdap. If additional doses are necessary for full tetanus protection, they may be administered as Td or Tdap.
Yes. Pneumococcal vaccines are all inactivated vaccines, which means you can give all other recommended vaccines at the same visit (using separate syringes) or at any later time with no waiting period following the vaccination. All currently available meningococcal vaccines in the United States may be administered without regard to the timing of pneumococcal vaccination.
No. Only the number of doses indicated in the manufacturer’s package insert should be withdrawn. For a 5.0 mL multidose vial of Fluzone, this is 10 doses. After the maximum number of doses has been withdrawn, discard the vial even if vaccine remains and the expiration date has not been reached.
Serious allergic reactions, such as anaphylaxis, in the minutes following vaccination are rare but are possible with any vaccine. CDC recommends that every vaccination site (regardless of vaccines being given) have staff available who are trained and equipped to recognize and respond to signs of anaphylaxis in a vaccine recipient.
Anaphylaxis following vaccination with mRNA COVID-19 vaccines is reported at a rate of approximately 5 cases per million doses administered.
An immediate severe allergic reaction to any component or previous dose of one COVID-19 vaccine type (the two types are mRNA or protein subunit) is a contraindication to vaccination with that type; however, CDC permits use of the alternate vaccine type for age-eligible patients in the usual vaccination setting, provided there is no additional contraindication to that product. CDC encourages consultation with an allergist-immunologist. See CDC’s COVID-19 interim clinical considerations section on contraindications and precautions for details: www.cdc.gov/covid/hcp/vaccine-considerations/contraindications-precautions.html.
No. HCP with written documentation of receipt of a complete, properly spaced HepB series AND a positive anti-HBs can be considered immune to HBV and require no further testing or vaccination. Testing unvaccinated or incompletely vaccinated HCP (including those without written documentation of vaccination) is not necessary and is potentially misleading because anti-HBs of 10 mIU/mL or higher as a correlate of vaccine-induced protection has only been determined for persons who have completed a HepB vaccination series. Persons who cannot provide written documentation of a complete HepB vaccination series should complete the series, then be tested for anti-HBs 1 to 2 months after the final dose.
ACIP has not addressed this issue specifically. Puncture wounds, however, should be attended to as soon as possible. The decision to delay a booster dose of tetanus toxoid-containing vaccine following an injury should be based on the nature of the injury and likelihood that the injured person is susceptible to tetanus. The more likely the person is to be susceptible, the more quickly that tetanus prophylaxis should be administered. A person with a tetanus-prone wound (e.g., punctures, wounds contaminated with soil or fecal material) and who has no history of tetanus immunization must be vaccinated and given tetanus immune globulin (TIG) as soon as possible. A person with a documented series of at least three tetanus toxoid-containing products, with a booster dose within the previous 10 years ago is less likely to be susceptible to tetanus, and the need for a booster dose is not as urgent, particularly if the wound can be thoroughly cleaned. The more likely a person is to be completely susceptible to tetanus (i.e., unvaccinated or incompletely vaccinated), the sooner that TIG and Td/Tdap should be administered, even if it means a trip to the emergency department.
No. The available data have been interpreted that any changes in antibody response to either vaccine’s components were clinically insignificant. If PCV20 and influenza vaccine are both indicated and recommended, they may be administered at the same visit.
CDC routinely recommends considering observation for 15 minutes after vaccination for syncope (fainting) or development of an immediate allergic reaction.
If you vaccinate a person who has an allergy-related precaution with the same COVID-19 vaccine type associated with that precaution, CDC recommends considering a 30-minute observation period and referral to an allergist-immunologist. CDC permits use of the alternate vaccine type in the usual vaccination setting. See www.cdc.gov/covid/hcp/vaccine-considerations/contraindications-precautions.html.
No. HCP who have documentation of receiving a complete HepB series and who tested positive for anti-HBs (defined as anti-HBs of 10 mIU/mL or higher) are considered to be immune to hepatitis B. Immunocompetent persons have long-term protection against HBV and do not need further testing or vaccine doses. Some immunodeficient persons (including those on hemodialysis) may need periodic booster doses of hepatitis B vaccine.
One dose of tetanus toxoid-containing vaccine (Tdap or Td) provides little or no protection. That is why tetanus immune globulin (TIG) is also recommended in this situation. See the Tetanus Prophylaxis for Wound Management section of the current ACIP statement, available at www.cdc.gov/mmwr/volumes/67/rr/pdfs/rr6702a1-H.pdf, pages 27–28. As far as timing, the toxoid and TIG should be given as soon as possible.
No. There are no data on the effectiveness of pneumococcal conjugate vaccine given by the intravenous route. The patient has renal disease, so it is important to ensure that the dose they receive is effective. CDC recommends repeating the dose using the correct route of administration (intramuscular).
Pneumococcal vaccination recommendations are complex, especially as newer conjugate vaccines are licensed and added to recommended options. Assessing what is needed for an individual patient of any age requires their age, pneumococcal vaccination history, and knowledge of any relevant high-risk conditions. There are several resources available from CDC and Immunize.org that can help:
CDC Resources:
Immunize.org Resources:
RIV is not licensed for people younger than 9 years of age, so there are no data regarding safety and efficacy in this age group. However, no serious side effects would be expected. The dose does not need to be repeated and should be considered valid. Even if no adverse reaction occurs, vaccine administration errors like this should be reported to the Vaccine Adverse Events Reporting System (VAERS) at www.vaers.hhs.gov.
No. The series should not be restarted. Continue the series from where you left off.
PPSV23 may be administered by intramuscular (IM) or subcutaneous (Subcut) routes. Pneumococcal conjugate vaccines are administered IM. Immunize.org has produced a simple handout that summarizes the dose, route, site, and needle length for administration of all recommended vaccines to adults and children: www.immunize.org/catg.d/p3085.pdf.
TIG is recommended for any wound other than a clean minor wound if the person’s vaccination history is either unknown, or the person has not had a full series of 3 doses of tetanus-containing vaccine. People with HIV infection or severe immunodeficiency who have contaminated wounds (including minor wounds) should also receive TIG, regardless of their history of tetanus immunizations. TIG should be given as soon as possible after the injury. The dose is 250 IU administered intramuscularly. See CDC’s web page for details: www.cdc.gov/tetanus/hcp/clinical-guidance/index.html.
For all licensed COVID-19 vaccines (Moderna [mNexspike, Spikevax], Sanofi-Novavax [Nuvaxovid], Pfizer-BioNTech [Comirnaty]) CDC encourages healthcare providers to report to the Vaccine Adverse Event Reporting System (VAERS) the following:
Information on how to submit a report to VAERS is available at https://vaers.hhs.gov or by calling 1-800-822-7967.
Because there is no documentation of vaccination, a vaccination series should be administered and postvaccination testing should be performed 1–2 months after the final dose of vaccine. There is no harm in receiving extra doses of vaccine. Postvaccination anti-HBs testing results should also be documented, including the date testing was performed. All healthcare settings should develop policies or guidelines to assure valid hepatitis B immunization.
The incubation period of tetanus ranges from 3 to 21 days, averaging about 10 days. In general, the further the injury site is from the central nervous system, the longer the incubation period. In the opinion of the tetanus experts at the CDC, for a person who has been vaccinated but is not up to date, there is probably little benefit in giving TIG more than a week or so after the injury. For a person believed to be completely unvaccinated, it is suggested to increase this interval to 3 weeks (i.e., up to day 21 post injury). Td or Tdap should be given concurrently with TIG.
All pneumococcal vaccines should be refrigerated at temperatures between 2°C (36°F) and 8°C (46°F). Do not freeze these vaccines. Vaccine exposed to freezing temperature should not be administered. For details of vaccine storage and handling, see the CDC Vaccine Storage and Handling Toolkit: www.cdc.gov/vaccines/hcp/downloads/storage-handling-toolkit.pdf.
If the error is discovered on the same clinic day, administer the remaining 0.25 mL of FluLaval that day. If it cannot be corrected that day, do not count the partial dose. Recall the child as soon as possible and administer a full age-appropriate dose of FluLaval, Fluarix, Fluzone, or Flucelvax.
Multiple national surveillance systems are used to monitor the safety of COVID-19 vaccines in different ways. CDC provides information about vaccine safety surveillance systems, with links to information about the safety of COVID-19 vaccines, here: www.cdc.gov/vaccine-safety/vaccines/covid-19.html.
No. A positive anti-HBs indicates that the vaccinated person is immune at the time the person was tested but does not assure that the person has long-term immunity. Long-term immunity has been demonstrated only for people attaining an adequate anti-HBs result of at least 10 mIU/mL after completing a full vaccination series. The most direct way to deal with this is to vaccinate the employee with a series of hepatitis B vaccine; test for anti-HBs in 1–2 months and document the result in the employee’s health record. An adequate anti-HBs result from a documented vaccine series would assure not only seroprotection, but long-term protection.
Each of these products must be stored at 2° to 8°C (36° to 46°F). They should not be frozen or exposed to freezing temperatures.
All 2026–27 influenza vaccines, including inactivated, recombinant, live attenuated, and mRNA vaccines, should be stored refrigerated at 2° through 8°C (36° through 46°F). Do not freeze influenza vaccine, and do not use vaccine that has been frozen. Follow each manufacturer’s package insert for product-specific handling and storage information.
V-safe is a safety monitoring system that vaccine recipients can use to share with CDC how they feel after vaccination. It was created initially for COVID-19 vaccines. Currently, recipients of RSV vaccines also may register for V-safe. To learn more about the program and how to guide vaccine recipients who wish to participate, visit CDC’s website: www.cdc.gov/vaccine-safety-systems/v-safe/index.html.
Do nothing. Data show that vaccine-induced anti-HBs levels might decline over time; however, immune memory (anamnestic anti-HBs response) remains intact following immunization. People with anti-HBs concentrations that decline to less than 10 mIU/mL are still protected against HBV infection. For healthcare professionals with normal immune status who have demonstrated adequate anti-HBs (at least 10 mIU/ mL) following full vaccination, booster doses of vaccine or periodic anti-HBs testing are not recommended.
No. COVID-19 vaccines are not currently part of the VICP. The COVID-19 vaccines are currently part of a similar program called the Countermeasures Injury Compensation Program (CICP). For more information, visit this web page: www.hrsa.gov/cicp.
No. There are no regulations that require removal from job situations where exposure to bloodborne pathogens could occur; this is an individual policy decision within the organization. OSHA regulations require that employees in jobs where there is a reasonable risk of exposure to blood be offered HepB vaccine. In addition, the regulation states that adequate personal protective equipment be provided and that standard precautions be followed. Check your state OSHA regulations regarding additional requirements. If there are no state OSHA regulations, federal OSHA regulations should be followed. Adequate documentation should be placed in the employee record regarding non-response to vaccination. HCP who do not respond to vaccination should be tested for HBsAg and total anti-HBc to determine if they have chronic HBV infection. If the HBsAg and total anti-HBc tests are positive, HCP should receive appropriate counseling for preventing transmission to others as well as referral for ongoing care to a specialist experienced in the medical management of chronic HBV infection. People who are HBsAg-positive and who perform exposure-prone procedures should seek counsel from a review panel comprised of experts with a balanced perspective (for example, infectious disease specialists and their personal physician[s]) regarding the procedures that they can perform safely. They should not be excluded from work. People who test negative for HBsAg should be considered susceptible to HBV infection and should be counseled about precautions to prevent HBV infection and the need to obtain HBIG prophylaxis for any known or likely exposure to HBsAg-positive blood (see Table).
For the 2026–2027 season, Comirnaty manufacturer-filled syringes (MFS), mNexspike MFS, and Nuvaxovid MFS all should be stored exclusively in the refrigerator at standard vaccine storage temperatures (between 2°C and 8°C [36°F and 46°F]) until the printed expiration date.
Spikevax MFS, if received frozen and never thawed, may be stored at ordinary vaccine freezer storage temperatures (between -50°C and -15°C [-58°F and 5°F]) until the printed expiration date. Once thawed, it may be stored at standard vaccine refrigerator temperatures (above) for up to 60 days or until the expiration date (whichever comes first).
Comirnaty single dose vials (SDV) for ages 6 months through 11 years, if received frozen and never thawed, may be maintained until the printed expiration date in an ultracold freezer between -90°C and -60°C (-130°F and -76°F). Once thawed, it may be stored at standard vaccine refrigerator temperatures (above) for up to 10 weeks, or until the expiration date, whichever comes first.
For further details, refer to the specific vaccine’s package insert. Immunize.org has assembled links to key COVID-19 vaccine resources, including package inserts, in the Checklist of Current Versions of U.S. COVID-19 Vaccination Guidance and Clinic Support Tools: www.immunize.org/catg.d/p3130.pdf.
Yes. HCP should not be discriminated against because of their hepatitis B status. All HCP should practice standard precautions, which are designed to prevent HBV transmission, both from patients to HCP and from HCP to patient. There is, however, one caveat concerning HBV-infected HCP. Those who have HBV levels 1000 IU/mL or 5000 genomic equivalents/mL or higher should not perform exposure-prone procedures (for example, gynecologic, cardiothoracic surgery) unless they have sought counsel from an expert review panel and been advised under what circumstances, if any, they may continue to perform these procedures. For more information on this issue, see “Updated CDC Recommendations for the Management of Hepatitis B Virus–Infected Health-Care Providers and Students,” MMWR, 2012; 61(RR03):1–12. This document is available at www.cdc.gov/mmwr/pdf/rr/rr6103.pdf.
Although routine transportation of vaccines to different facilities is not generally recommended, there are times when this is necessary. CDC recommends transporting COVID-19 vaccine in unopened vials or manufacturer-filled syringes (MFS) and always with a continuous temperature monitoring device to ensure adherence to authorized storage times and temperatures. See the product package insert for details on permissible conditions for transport.
Yes. HepB vaccines have been demonstrated to be safe when administered to infants, children, adolescents, and adults. Since 1982, well over 100 million people, including infants, children, and adults living in the United States have received at least one dose of HepB vaccine; more than a billion doses of HepB vaccine have been given worldwide. Vaccination causes a sore arm occasionally, but serious reactions are very rare.
Many years of experience with Engerix-B and Recombivax HB vaccines and recent studies of Heplisav-B indicate no apparent risk for adverse events to a developing fetus. Current vaccines contain noninfectious HBsAg and pose no risk to the fetus. If the mother is being vaccinated because of a risk factor for HBV infection (for example, a healthcare worker, a person with a sexually transmitted disease, an injection drug user, a person with multiple sex partners), vaccination should be initiated as soon as the risk factor is identified during the pregnancy. HBV infection during pregnancy might result in severe disease for the mother and chronic infection for the newborn.
Any of the available HepB vaccines (Engerix-B, Heplisav-B, Recombivax HB) or the HepA-HepB combination vaccine, Twinrix, may be used during pregnancy.
No. Administration of HepB soon after birth has not been associated with an increased rate of elevated temperatures or subsequent evaluations for possible sepsis in the first 21 days of life.
A serious allergic reaction to a prior dose of HepB or a vaccine component is a contraindication to further doses of HepB. Engerix-B, Recombivax HB, Twinrix, and Heplisav-B are synthesized in yeast cells into which a plasmid containing the gene for HBsAg has been inserted. People with a severe allergic reaction to yeast should not be vaccinated with vaccines produced in yeast cells.
As with other vaccines, vaccination of people with moderate or severe acute illness, with or without fever, should be deferred until the illness improves. Vaccination is not contraindicated in people with a history of multiple sclerosis, Guillain-Barré syndrome, or autoimmune diseases such as systemic lupus erythematosus or rheumatoid arthritis.
All hepatitis B-containing vaccines should be stored at refrigerator temperature at 2°C to 8°C (36°F to 46°F). The vaccines must not be frozen. Any vaccine exposed to freezing temperature should not be used. Do not use these or any other vaccines after the expiration date shown on the packaging. Any vaccine administered after its expiration date should be repeated.
