FAQs for the Interim Clinical Considerations for COVID-19 Vaccination

Vaccination Schedule and Use

Yes. For primary series vaccination, Moderna, Pfizer-BioNTech, and Novavax COVID-19 vaccines are recommended. For booster vaccination, Moderna and Pfizer-BioNTech are recommended.

Novavax COVID-19 vaccine for booster vaccination and Janssen COVID-19 Vaccine for primary series and booster vaccination should only be used in limited situations.

For more information, see COVID-19 vaccines.

No. You should administer the second dose as close as possible to the recommended interval after the first dose. However, if the second dose is administered after this interval, there is no need to restart the series.

An 8-week interval might be optimal for some people, especially males ages 12–39 years because of the small risk of myocarditis and pericarditis associated with Moderna, Novavax, and Pfizer-BioNTech COVID-19 vaccines. Vaccine effectiveness might also be increased with an interval longer than 3 or 4 weeks.

For additional information on the vaccination schedule, see:

Yes. Doses administered up to 4 days before the minimum interval, known as the 4-day grace period, are considered valid. This applies to primary series and booster doses of vaccine. Do not use the grace period to schedule doses.

If a dose is administered earlier than the grace period, see Appendix D for guidance on corrective actions. It is considered a vaccine administration error; you are required to report COVID-19 vaccine administration errors to the Vaccine Adverse Event Reporting System (VAERS).

Doses administered at any time after the recommended interval are valid.

For more information, see timing, spacing, age transitions, and interchangeability of COVID-19 vaccines.

In accordance with general best practices for immunizations, routine administration of all age-appropriate doses of vaccines simultaneously is recommended for children, adolescents, and adults for whom no specific contraindications exist at the time of the healthcare visit. This includes simultaneous administration of COVID-19 vaccine and other vaccines. However, there are additional considerations for Moderna, Novavax, and Pfizer-BioNTech COVID-19 vaccines if administering an orthopoxvirus (monkeypox) vaccine.

For more information, see Coadministration of COVID-19 vaccines with other vaccines.

People who previously received COVID-19 vaccination (i.e., Moderna, Novavax, or Pfizer-BioNTech) may be given orthopoxvirus vaccine (either JYNNEOS or ACAM2000) without a minimum interval between vaccinations.

People who previously received orthopoxvirus vaccination (either JYNNEOS or ACAM2000), particularly adolescent or young adult males, might consider waiting 4 weeks before receiving a COVID-19 vaccine (i.e., Moderna, Novavax, or Pfizer-BioNTech) because of the observed risk for myocarditis and pericarditis after receipt of ACAM2000 orthopoxvirus vaccine and COVID-19 vaccines (i.e., Moderna, Novavax, or Pfizer-BioNTech) and the unknown risk for myocarditis and pericarditis after JYNNEOS administration.

For more information, see:

Vaccine Dosage and Formulation

In general, CDC recommends that people receive the age-appropriate vaccine dosage based on their age on the day of vaccination. If a person moves from a younger age group to an older age group during the primary series or between the primary series and receipt of the booster dose, they should receive the vaccine dosage for the older age group for all subsequent doses with the following exception: The Food and Drug Administration (FDA) authorization requires that children who receive the Pfizer-BioNTech COVID-19 Vaccine and transition from age 4 years to 5 years during the primary series must complete the series they start.

FDA authorization allows for dosing options for certain other age transitions when a child ages from a younger to older age group. For more information see:

If the incorrect formulation is administered:

  • Resulting in a higher-than-authorized dose: Do not repeat dose.
  • Resulting in a lower-than-authorized dose: Repeat the dose immediately (no minimum interval) with the age-appropriate dose and formulation. Some experts suggest delaying the repeat dose for 8 weeks after the invalid dose based on the potential for increased reactogenicity and the rare risk of myocarditis and pericarditis associated with Moderna, Novavax, and Pfizer-BioNTech vaccines, especially in males ages 12–39 years. See Considerations for extended intervals for COVID-19 vaccine primary series.

For more information on transitioning between age groups, see

All COVID-19 primary series doses should be from the same manufacturer.

In the following exceptional situations, a different COVID-19 vaccine may be administered to complete a primary series at a minimum interval of 28 days from the last COVID-19 vaccine dose:

  • The same vaccine is not available
  • A previous dose is unknown
  • The person would otherwise not complete the primary series
  • A person starts but is unable to complete a primary series with the same COVID-19 vaccine due to a contraindication.

No VAERS report is required.

For more information, see:

The bivalent mRNA vaccines (i.e., Moderna and Pfizer-BioNTech) are not currently authorized to be used for the primary series with the following exception: children ages 6 months–4 years who received 2 primary series doses of a monovalent Pfizer-BioNTech vaccine should receive a bivalent Pfizer-BioNTech vaccine for their third primary series dose.

If a bivalent Pfizer-BioNTech vaccine is administered in error for a primary series dose: Do not repeat the dose. The primary and booster dosages are the same; the bivalent dose can be counted as a primary series dose. Continue with the recommended vaccination schedule (i.e., complete the primary series with a monovalent Pfizer-BioNTech vaccine, then administer a bivalent booster dose at least 2 months after completion of the primary series).

If a bivalent Moderna vaccine is administered for a primary dose: Repeat the dose immediately (no minimum interval) with a monovalent Moderna vaccine because administration of the bivalent Moderna vaccine will result in a lower-than-authorized primary series dosage. Some experts suggest delaying the repeat dose for 8 weeks after the invalid dose. After the dose has been repeated, continue with the recommended vaccination schedule (i.e., complete the primary series with a monovalent Moderna vaccine, then administer a bivalent booster dose at least 2 months after completion of the primary series).

Both situations are considered vaccine administration errors and should be reported to Vaccine Adverse Event Reporting System (VAERS).

For more information, see

No, the monovalent mRNA vaccines (i.e., Moderna or Pfizer-BioNTech) are not authorized for use as a booster dose; they can only be used for the primary series. A bivalent mRNA vaccine is recommended for the booster dose.

If a patient accidently received a monovalent mRNA vaccine for the booster dose, the dose generally does not need to be repeated. However, providers may administer 1 bivalent booster dose as a repeat dose based on clinical judgment and patient preference. The repeat dose should be administered at least 2 months after the monovalent booster dose.

For more information, see vaccine administration errors and deviations.

Children ages 6 months–4 years who received 1 monovalent Moderna and 1 monovalent Pfizer-BioNTech vaccine dose for the first two doses of the primary series (in any order: Moderna then Pfizer-BioNTech or Pfizer-BioNTech then Moderna) should follow a 3-dose primary series schedule. The third primary series dose can be either a monovalent Moderna vaccine or a bivalent Pfizer-BioNTech vaccine.

Currently, children in this age group who receive a mixed 3-dose primary series with any combination of Moderna and Pfizer-BioNTech vaccines may not receive any booster dose.

For more information, see Interchangeability of COVID-19 vaccine products.

Booster Doses

Everyone ages 6 months and older is recommended to receive 1 bivalent mRNA booster dose after completion of any FDA-approved or FDA-authorized monovalent primary series or previously received monovalent booster dose(s) with the following exception: children age 6 months–4 years who receive a 3-dose Pfizer-BioNTech primary series are not authorized to receive a booster dose at this time regardless of which Pfizer-BioNTech vaccine (i.e., monovalent or bivalent) was administered for the third primary series dose.

For more information on booster doses see schedules for:

For booster dose recommendations for people vaccinated outside the United States, see people who received COVID-19 vaccine outside the United States.

Ages 6 months – 4 years and completed the Moderna primary series: 1 bivalent Moderna booster dose.

Ages 6 months – 4 years and completed Pfizer-BioNTech primary series: No booster dose is recommended at this time.

Age 5 years and completed Moderna primary series: 1 bivalent mRNA booster dose (Moderna or Pfizer-BioNTech).

Age 5 years and received Pfizer-BioNTech primary series: 1 bivalent Pfizer-BioNTech booster dose.

Ages 6 years and older: 1 bivalent mRNA booster dose (Moderna or Pfizer-BioNTech) regardless of which vaccine they received for their primary series.

Novavax monovalent COVID-19 Vaccine may be used as a booster dose in limited situations for people ages 18 years and older.

For more information on booster doses see schedules for:

For booster dose recommendations for people vaccinated outside the United States, see people who received COVID-19 vaccine outside the United States.

The bivalent booster dose is administered at least 2 months after completion of the primary series. The interval is the same regardless of which vaccine was administered for the primary series and which bivalent booster (Moderna or Pfizer-BioNTech) will be administered.

Yes. People who previously received 1 or more monovalent booster doses, are recommended to receive 1bivalent booster dose; it should be administered at least 2 months after the last monovalent booster dose.

Children ages 6 months–4 years who completed the Moderna primary series are recommended to receive 1 bivalent Moderna booster dose. Booster doses for children ages 6 months–4 years who completed the Pfizer-BioNTech primary series are not currently authorized.

No, children ages 6 months–4 years who have completed the 3-dose Pfizer-BioNTech primary series with monovalent vaccine cannot get a dose of bivalent Pfizer-BioNTech vaccine. Children in this age group who have not yet received the third Pfizer-BioNTech primary dose are recommended to receive a bivalent Pfizer-BioNTech dose as the third primary dose.

Yes. The child should receive 1 bivalent Pfizer-BioNTech booster dose when they turn age 5 years, and it has been at least 2 months since completing their primary series.  A child can get the bivalent booster dose regardless of whether the third primary series dose was a monovalent or bivalent Pfizer-BioNTech vaccine.

Children age 5 years who completed the Moderna primary series are recommend to receive 1 bivalent mRNA booster dose (Moderna or Pfizer-BioNTech). Children age 5 years who completed the Pfizer-BioNTech primary series are recommended to receive 1 bivalent Pfizer-BioNTech booster dose; they cannot get a Moderna booster dose.

Currently, a child in this age group who received a mixed 3-dose primary series with any combination of Moderna and Pfizer-BioNTech vaccines is not authorized to receive any booster dose. When a child who received a mixed primary dose series turns age 5 years, the child may receive 1 bivalent booster dose with either Moderna or Pfizer-BioNTech vaccine.

For more information, see Interchangeability of COVID-19 vaccine products.

The monovalent Novavax COVID-19 vaccine is authorized for a booster dose in limited situations. People ages 18 years and older who completed primary vaccination using any COVID-19 vaccine and have not received any previous booster dose(s) (including any previous monovalent or bivalent mRNA booster dose[s]) may receive a monovalent Novavax booster dose at least 6 months after completion of the primary series if they are unable to receive an mRNA vaccine (i.e., mRNA vaccine contraindicated or not available) or unwilling to receive an mRNA vaccine and would otherwise not receive a booster dose.

People who are Moderately or Severely Immunocompromised

Yes. For COVID-19 vaccination guidance for people who are moderately or severely immunocompromised people, please refer to:

People can self-attest to their moderately or severely immunocompromised status and should be vaccinated according to the schedule for people who are moderately or severely immunocompromised. Vaccinators and clinic administrators should not deny COVID-19 vaccination to a person because of a lack of documentation.

Patients who undergo HCT or CAR-T-cell therapy should be revaccinated for the monovalent primary series and bivalent mRNA booster dose received before or during treatment. There is no revaccination for monovalent mRNA booster dose(s) received before or during treatment. After revaccination with the primary series, the patient should receive 1 bivalent mRNA booster dose.

Below are three scenarios and the recommended action:

If your patient received the primary series before or during treatment: Revaccinate the patient with the primary series and administer 1 bivalent mRNA booster dose at least 2 months after repeating the primary series.

If your patient received the primary series and 1 or 2 (or more) monovalent booster doses before or during treatment: Revaccinate the patient with the primary series. Do not revaccinate for the monovalent mRNA booster dose(s). The patient is recommended to receive 1 bivalent mRNA booster dose at least 2 months after repeating the primary series.

If your patient received the primary series and a bivalent booster dose before or during treatment: Revaccinate the patient with the primary series and 1 bivalent mRNA booster dose.

For more information, see considerations for COVID-19 revaccination.

No. Because variants of SARS-CoV-2 currently circulating in the United States are resistant to EVUSHELDTM, EVUSHELDTM is not currently authorized for use in the United States for pre-exposure prophylaxis. Everyone ages 6 months and older, including people who are moderately or severely immunocompromised, are recommended to receive COVID-19 vaccination according to the current schedule.

For more information on staying up-to-date with COVID-19 vaccination, see the COVID-19 vaccination schedule for people who are moderately or severely immunocompromised.

Yes. Everyone ages 6 months and older is recommend to be vaccinated against COVID-19, including people who are moderately or severely immunocompromised and who previously received EVUSHELD™ for pre-exposure prophylaxis.

COVID-19 vaccines can be administered any time after receipt of EVUSHELD™.

For more information on staying up-to-date with COVID-19 vaccination, see the COVID-19 vaccination schedule for people who are moderately or severely immunocompromised.

Vaccination and SARS-CoV-2 Laboratory Testing

Antibody testing is not currently recommended to assess the need for vaccination in an unvaccinated person or to assess immunity to SARS-CoV-2 following COVID-19 vaccination or after SARS-CoV-2 infection. Antibody tests for SARS-CoV-2 look for the presence of antibodies made in response to a previous infection or vaccination. Antibodies are an indicator of the body’s efforts to fight off the SARS-CoV-2 virus. None of the currently authorized SARS-CoV-2 antibody tests have been validated to evaluate specific immunity or protection from SARS-CoV-2 infection.

For assistance with patient counseling and education related to COVID-19 testing and vaccination, see:

For more detailed information, see: Interim Guidelines for COVID-19 Antibody Testing.

Vaccination and SARS-CoV-2 Infection

CDC recommends COVID-19 vaccination for all people ages 6 months and older, including people with a history of SARS-CoV-2 infection.

Prior infection: Offer vaccination regardless of history of prior symptomatic or asymptomatic SARS-CoV-2 infection, including to people with prolonged post-COVID-19 symptoms and people who experienced SARS-CoV-2 infection (symptomatic or asymptomatic) after vaccination. People who recently had SARS-CoV-2 infection may consider delaying their primary series or booster COVID-19 vaccine dose by 3 months from symptom onset or positive test (if infection was asymptomatic).

Current infection: Defer vaccination of people with known current SARS-CoV-2 infection until the person has recovered from acute illness (if the person has symptoms) and until criteria have been met for them to discontinue isolation.

Laboratory testing is not recommended for the purpose of vaccine decision-making.

For more information, see COVID-19 vaccination and SARS-CoV-2 infection.

Considerations Involving Pregnancy, Lactation, and Fertility

Yes. CDC recommends COVID-19 vaccination for all people who are pregnant, breastfeeding, recently pregnant, trying to get pregnant now, or who might become pregnant in the future. Monovalent mRNA (Moderna or Pfizer-BioNTech) and Novavax vaccines are recommended for the primary series and a bivalent mRNA vaccine (Moderna or Pfizer-BioNTech) is recommended for the booster dose for all vaccine-eligible populations including people who are pregnant or lactating. Those who are considering receipt of the Janssen COVID-19 Vaccine should see Appendix A: Guidance for use of Janssen COVID-19 Vaccine.

For more information, see COVID-19 Vaccines While Pregnant or Breastfeeding.

Special Populations and Situations

In accordance with general best practices, preterm infants (infants born before 37 weeks’ gestation), regardless of birth weight, should receive COVID-19 vaccination at their chronological age and according to the same schedule and guidance as for full-term infants and children.

Infants of mothers who were vaccinated and/or had COVID-19 or SARS-CoV-2 infection before or during pregnancy should be vaccinated according to the recommended schedule.

People who previously received SARS-CoV-2 antibody products (anti-SARS-CoV-2 monoclonal antibodies or convalescent plasma) as part of COVID-19 treatment, post-exposure prophylaxis, or pre-exposure prophylaxis can be vaccinated at any time; COVID-19 vaccination does not need to be delayed following receipt of monoclonal antibodies or convalescent plasma.

Rare cases of Bell’s palsy (acute peripheral facial nerve palsy) were reported following vaccination of participants in mRNA COVID-19 vaccine clinical trials, but FDA was not able to determine whether these cases were causally related to vaccination. People with a history of Bell’s palsy may receive any currently FDA-approved or FDA-authorized COVID-19 vaccine: mRNA (i.e., Moderna or Pfizer-BioNTech) and Novavax COVID-19 vaccines are recommended for the primary series and an age-appropriate mRNA vaccine is recommend for the booster dose.

For more information on the recommended vaccination, see COVID-19 vaccination schedule for people who are not moderately or severely immunocompromised.

GBS is a neurological disorder in which the body’s immune system damages nerve cells, causing muscle weakness and sometimes paralysis. For people with a history of GBS, as for the general population, mRNA (i.e., Moderna or Pfizer-BioNTech) and Novavax COVID-19 vaccines are recommended for the primary series, and an age-appropriate mRNA vaccine is recommended for the booster dose. No increased risk of GBS has been identified with receipt of mRNA COVID-19 vaccines.

See Guidance for use of Janssen COVID-19 Vaccine and Use of the Janssen (Johnson & Johnson) COVID-19 Vaccine  for information on GBS and Janssen COVID-19 Vaccine.

For more information on the recommended vaccination schedule, see COVID-19 vaccination schedule for people who are not moderately or severely immunocompromised.