Interim Clinical Considerations for Use of COVID-19 Vaccines in the United States

These clinical considerations provide information to healthcare professionals and public health officials on use of COVID-19 vaccines. They are informed by:

• Recommendations of the Advisory Committee on Immunization Practices (ACIP) and the Centers for Disease Control and Prevention (CDC)
• COVID-19 vaccine approval (licensure) under a Biologics License Application (BLA) or authorization under an Emergency Use Authorization (EUA) by the U.S. Food and Drug Administration (FDA)
• CDC’s Emergency Use Instructions (EUI) for FDA-approved vaccines
• Emergency Use Listing (EUL) of COVID-19 vaccines by the World Health Organization (WHO)
• ACIP’s General Best Practice Guidelines for Immunization
• Expert opinion

Two types of COVID-19 vaccines are available for use in the United States:

• mRNA vaccines
  • Moderna COVID-19 Vaccine (2023–2024 Formula) is authorized for children ages 6 months–11 years; SPIKEVAX is the licensed Moderna product for people ages 12 years and older. These vaccines are hereafter referred to as updated (2023–2024 Formula) Moderna COVID-19 Vaccine.
  • Pfizer-BioNTech COVID-19 Vaccine (2023–2024 Formula) is authorized for children ages 6 months–11 years; COMIRNATY is the licensed Pfizer-BioNTech product for people ages 12 years and older. These vaccines are hereafter referred to as updated (2023–2024 Formula) Pfizer-BioNTech COVID-19 Vaccine.
• Protein subunit vaccine
  • Novavax COVID-19 Vaccine, Adjuvanted (hereafter referred to as Novavax COVID-19 Vaccine) is authorized for people ages 12 years and older for primary vaccination and, in certain limited situations, as a booster dose in people ages 18 years and older.

COVID-19 vaccine composition

• Moderna and Pfizer-BioNTech COVID-19 vaccines: The 2023–2024 formulation has been updated to a monovalent vaccine based on the Omicron XBB.1.5 sublineage of SARS-CoV-2. The bivalent formulation (Original and Omicron BA.4/BA.5) should no longer be used.
• Novavax COVID-19 Vaccine is currently formulated as a monovalent vaccine based on the Original strain of SARS-CoV-2.

COVID-19 vaccine-specific package inserts and FDA fact sheets and U.S. COVID-19 Vaccine Product Information can be consulted for a full list of ingredients and information on the conditions of use, storage and handling, preparation, and administration procedures.

Groups recommended for vaccination

COVID-19 vaccination is recommended for everyone ages 6 months and older in the United States for the prevention of COVID-19. There is currently no FDA-approved or FDA-authorized COVID-19 vaccine for children younger than age 6 months. CDC recommends that people stay up to date with COVID-19 vaccination.

Vaccination schedules can be found in Table 1 for people who are not moderately or severely immunocompromised and in Table 2 for people who are moderately or severely immunocompromised. See Appendix A for recommendations for people who received COVID-19 vaccine outside the United States.

Vaccine dosage and administration

In general, CDC recommends that people receive the age-appropriate vaccine product and dosage based on their age on the day of vaccination and in accordance with the recommended intervals for that age group (1). However, for COVID-19 vaccination there is an exception for children who receive the Pfizer-BioNTech COVID-19 Vaccine and transition from age 4 years to 5 years during the 3-dose vaccination series (see Transitioning from a younger to older age group).

Vaccine doses should be administered by the intramuscular route.

The COVID-19 vaccination schedule for people who are not moderately or severely immunocompromised is detailed in Table 1.

Updated (2023–2024 Formula) mRNA vaccines

The number of updated (2023–2024 Formula) mRNA vaccine doses an individual needs is based on age and vaccination history.

• Children ages 6 months–4 years who are unvaccinated are recommended to receive 2 or 3 homologous (i.e., from the same manufacturer) updated (2023–2024 Formula) mRNA vaccine doses, depending on vaccine manufacturer.
• Children ages 6 months–4 years who previously received Original monovalent or bivalent mRNA vaccine doses are recommended to complete the vaccination series with 1 or 2 homologous updated (2023–2024 Formula) mRNA vaccine doses, depending on vaccine manufacturer and the number of previous vaccine doses. Children in this age group who received all doses in the initial vaccination series should receive 1 dose of a homologous updated (2023–2024 Formula) mRNA vaccine.
• People ages 5 years and older who are unvaccinated or previously received any number of Original monovalent or bivalent mRNA vaccine doses are recommended to receive 1 dose of an updated (2023–2024 Formula) mRNA vaccine from either manufacturer.
• People ages 12 years and older who previously received 1 or more doses of Novavax COVID-19 Vaccine or Janssen COVID-19 Vaccine, including those who also received any mRNA vaccine dose(s), are recommended to receive 1 dose of an updated (2023–2024 Formula) mRNA vaccine from either manufacturer.

Novavax COVID-19 Vaccine

Novavax COVID-19 Vaccine is currently authorized to provide:

• A 2-dose primary series to people ages 12 years and older. The primary series doses are separated by 3–8 weeks. An 8-week interval between the first and second primary series doses might be optimal for some people ages 12–64 years, especially for males ages 12–39 years, as it might reduce the small risk of myocarditis and pericarditis associated with this vaccine.
• A booster dose in limited situations to people ages 18 years and older who previously completed primary vaccination using any FDA-approved or FDA-authorized COVID-19 vaccine; have not received any previous booster dose(s); and are unable (i.e., mRNA vaccine contraindicated or vaccine not available) or unwilling to receive an mRNA vaccine and would otherwise not receive a booster dose. The Novavax booster dose is administered at least 6 months after completion of any primary series.

Table 1. Recommended COVID-19 vaccination schedule for people who are not moderately or severely immunocompromised by COVID-19 vaccination history, September 15, 2023

Updated (2023–2024 Formula) mRNA COVID-19 vaccines

Ages 6 months–4 years

Ages 5–11 years^‡

Ages 12 years and older

Special situation: For children ages 6 months–4 years who received 1 dose of Moderna and 1 dose of Pfizer-BioNTech, see the section on Interchangeability for guidance on completing the initial vaccination series.

People ages 65 years and older are recommended to receive 1 dose of updated (2023–2024 Formula) mRNA vaccine; an additional dose of COVID-19 vaccine is not recommended at this time. ACIP will continue to evaluate available data on the epidemiology of COVID-19 and the safety and effectiveness of COVID-19 vaccines. Based on these assessments, ACIP will update COVID-19 vaccine policy and guidance as needed, especially for people at increased risk for severe COVID-19, including people ages 65 years and older.

An 8-week interval between the first and second mRNA COVID-19 vaccine (Moderna, Pfizer-BioNTech) doses and between the first and second doses of Novavax COVID-19 Vaccine might be optimal for some people as it might reduce the small risk of myocarditis and pericarditis associated with these COVID-19 vaccines. Under the current COVID-19 vaccination schedule, the extended interval applies only to children ages 6 months–4 years, depending on their vaccination history (Table 1), and people ages 12 years and older receiving Novavax vaccine.

While absolute risk remains small, an elevated risk for myocarditis and pericarditis has been observed among mRNA COVID-19 vaccine recipients, particularly in males ages 12–39 years (see COVID-19 vaccination and myocarditis and pericarditis for additional information). Cases of myocarditis and pericarditis were identified in clinical trials of Novavax COVID-19 Vaccine and through passive surveillance during post-authorization use outside the United States.

A 3-week interval between the first and second doses of Novavax and Pfizer-BioNTech COVID-19 vaccines and a 4-week interval between the first and second doses of Moderna COVID-19 Vaccine continue to be recommended for people who are moderately or severely immunocompromised, adults ages 65 years and older, and in situations when the fullest possible protection needs to be achieved sooner (e.g., increased concern about an individual’s higher risk for severe disease).

The COVID-19 vaccination schedule for people who are moderately or severely immunocompromised is detailed in Table 2.

People who are or who become moderately or severely immunocompromised should follow the COVID-19 vaccination schedule according to their age and immune status at the time of eligibility for that dose; see Considerations for timing of COVID-19 vaccination in relation to immunosuppressive therapies for vaccination of people who will shortly become moderately or severely immunocompromised (e.g., prior to organ transplant) and Considerations for COVID-19 revaccination.

Updated (2023–2024 Formula) mRNA vaccines

The number of recommended updated (2023–2024 Formula) mRNA vaccine doses for an individual who is moderately or severely immunocompromised is based on vaccination history and the vaccine manufacturer (Moderna, Novavax, or Pfizer-BioNTech).

• People ages 6 months and older who are unvaccinated are recommended to receive 3 homologous (i.e., from the same manufacturer) updated (2023–2024 Formula) mRNA vaccine doses.
• People ages 6 months and older who previously received 1 or 2 Original monovalent or bivalent mRNA vaccine doses are recommended to complete the 3-dose series with 2 or 1 homologous updated (2023–2024 Formula) mRNA vaccine doses, respectively.
• People ages 6 months and older who previously received a combined total of at least 3 Original monovalent or bivalent mRNA vaccine doses are recommended to receive 1 dose of updated (2023–2024 Formula) mRNA vaccine:
  • For those ages 6 months–4 years, only a homologous dose may be administered.
  • For those ages 5 years and older, a dose from either manufacturer may be administered.
• People who have received at least 3 mRNA COVID-19 vaccine doses, including 1 dose of updated (2023–2024 Formula) mRNA vaccine, may receive 1 or more additional updated (2023–2024 Formula) mRNA vaccine doses:
  • For those ages 6 months–4 years, only homologous additional dose(s) may be administered.
  • For those ages 5 years and older, a dose from either manufacturer may be administered.
• People ages 12 years and older who previously received Novavax COVID-19 Vaccine or Janssen COVID-19 Vaccine, including those who received any mRNA vaccine dose(s), are recommended to receive 1 dose of updated (2023–2024 Formula) mRNA vaccine from either manufacturer.
  • These people may receive 1 or more additional updated (2023–2024 Formula) mRNA vaccine doses from either manufacturer.

Novavax COVID-19 Vaccine

Novavax COVID-19 Vaccine is currently authorized to provide:

• A 2-dose primary series to people ages 12 years and older. The primary series doses are separated by 3 weeks.
• A booster dose in limited situations to people ages 18 years and older who previously completed primary vaccination using any FDA-approved or FDA-authorized COVID-19 vaccine; have not received any previous booster dose(s); and are unable (i.e., contraindicated or vaccine not available) or unwilling to receive an mRNA vaccine and would otherwise not receive a booster dose. The Novavax booster dose is administered at least 6 months after completion of any primary series.

Table 2. Recommended COVID-19 vaccination schedule for people who are moderately or severely immunocompromised by COVID-19 vaccination history, September 15, 2023

Updated (2023–2024 Formula) mRNA vaccines

Ages 6 months–4 years

Ages 5–11 years*

Ages 12 years and older^*

Special situation: For people ages 6 months and older who are moderately or severely immunocompromised and received 1 dose of Moderna and 1 dose of Pfizer-BioNTech, see the section on Interchangeability for guidance on completing the initial vaccination series.

Moderate and severe immunocompromising conditions and treatments include but are not limited to:

• Active treatment for solid tumor and hematologic malignancies
• Hematologic malignancies associated with poor responses to COVID-19 vaccines regardless of current treatment status (e.g., chronic lymphocytic leukemia, non-Hodgkin lymphoma, multiple myeloma, acute leukemia)
• Receipt of solid-organ transplant or an islet transplant and taking immunosuppressive therapy
• Receipt of chimeric antigen receptor (CAR)-T-cell therapy or hematopoietic cell transplant (HCT) (within 2 years of transplantation or taking immunosuppressive therapy)
• Moderate or severe primary immunodeficiency (e.g., common variable immunodeficiency disease, severe combined immunodeficiency, DiGeorge syndrome, Wiskott-Aldrich syndrome)
• Advanced HIV infection (people with HIV and CD4 cell counts less than 200/mm³, history of an AIDS-defining illness without immune reconstitution, or clinical manifestations of symptomatic HIV) or untreated HIV infection
• Active treatment with high-dose corticosteroids (i.e., 20 mg or more of prednisone or equivalent per day when administered for 2 or more weeks), alkylating agents, antimetabolites, transplant-related immunosuppressive drugs, cancer chemotherapeutic agents classified as severely immunosuppressive, tumor necrosis factor (TNF) blockers, and other biologic agents that are immunosuppressive or immunomodulatory (e.g., B-cell-depleting agents)

Factors to consider in assessing the general level of immune competence in a patient include disease severity, duration, clinical stability, complications, comorbidities, and any potentially immune-suppressing treatment.

For additional information about the degree of immune suppression associated with different medical conditions and treatments, providers can consult ACIP’s General Best Practice Guidelines for Immunizations, the CDC Yellow Book, and the Infectious Diseases Society of America policy statement, 2013 IDSA Clinical Practice Guideline for Vaccination of the Immunocompromised Host.

People can self-attest to their moderately or severely immunocompromised status and receive COVID-19 vaccine doses wherever vaccines are offered. Vaccinators should not deny COVID-19 vaccination to a person due to lack of documentation.

Recipients of HCT or CAR-T-cell therapy who received 1 or more doses of COVID-19 vaccine prior to or during treatment should be revaccinated. Revaccination should start at least 3 months (12 weeks) after transplant or CAR-T-cell therapy and should follow the currently recommended schedule for people who are unvaccinated (Table 2).

Revaccination may also be considered for patients who received 1 or more doses of COVID-19 vaccine during treatment with B-cell-depleting therapies (e.g., rituximab, ocrelizumab) that were administered over a limited period (e.g., as part of a treatment regimen for certain malignancies) according to the currently recommended schedule (Table 2). The suggested interval to start revaccination is about 6 months after completion of the B-cell-depleting therapy. Timing of vaccination for patients who receive B-cell-depleting therapies on a continuing basis (e.g., for treatment of certain autoimmune conditions such as rheumatoid arthritis or multiple sclerosis) is addressed in Considerations for timing of COVID-19 vaccination in relation to immunosuppressive therapies.

A patient’s clinical team is best positioned to determine the degree of immune compromise, need for revaccination, and appropriate timing of revaccination.

Administration of COVID-19 vaccines should not be delayed in patients taking immunosuppressive therapies. Whenever possible, COVID-19 vaccines should be administered at least 2 weeks before initiation or resumption of immunosuppressive therapies. For patients who receive B-cell-depleting therapies on a continuing basis, COVID-19 vaccines should be administered approximately 4 weeks before the next scheduled therapy.

Timing of COVID-19 vaccination should take into consideration:

• Current or planned immunosuppressive therapies
• Optimization of both the patient’s medical condition and anticipated response to vaccination
• Individual benefits and risks

On a case-by-case basis, providers caring for these patients may administer Moderna, Novavax, and Pfizer-BioNTech COVID-19 vaccines outside of the FDA and CDC dosing intervals when, based on their clinical judgment, the benefits of vaccination are deemed to outweigh the potential and unknown risks for the recipient who is immunocompromised.

The utility of serologic testing, cellular immune testing, or B-cell quantification to assess immune response to vaccination and guide clinical care has not been established. Such testing outside of the context of research studies is not recommended at this time.

Doses administered up to 4 days before the minimum interval or age, known as the 4-day grace period, are considered valid. If a dose is administered prior to the 4-day grace period, see Appendix B. Doses administered at any time after the recommended interval are valid.

In general, CDC recommends that people receive the age-appropriate vaccine product and dosage based on their age on the day of vaccination (Table 1 and Table 2).

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 with one exception:

• The FDA EUA provides that children who transition from age 4 years to age 5 years during the Pfizer-BioNTech COVID-19 vaccination series complete the 3-dose series with updated (2023–2024 Formula) Pfizer-BioNTech COVID-19 Vaccine for ages 6 months–4 years, 0.3 mL/3 ug (yellow cap; yellow label).

In addition, the FDA EUA provides that children who transition from age 4 years to age 5 years during the Moderna vaccination series complete the 2-dose series; there is no dosage change.

In accordance with General Best Practice Guidelines for Immunization, routine administration of all age-appropriate doses of vaccines simultaneously, also known as coadministration, is recommended for children, adolescents, and adults if there are no contraindications at the time of the healthcare visit. Simultaneous administration is defined as administering more than one vaccine on the same clinic day, at different anatomic sites, and not combined in the same syringe. Providers may simultaneously administer COVID-19, influenza, and respiratory syncytial virus (RSV) vaccines to eligible patients; the Health Alert Network (HAN) published on September 5, 2023 may be consulted for additional information about simultaneous administration of these vaccines.

There are additional considerations for simultaneous administration of an orthopoxvirus vaccine and COVID-19 vaccine as follows:

• There is no required minimum interval between receiving a dose of any COVID-19 vaccine and an orthopoxvirus vaccine, either JYNNEOS or ACAM2000 vaccine (e.g., for mpox prevention), regardless of which vaccine is administered first.
• Use of JYNNEOS vaccine should be prioritized over ACAM2000 when co-administering a COVID-19 vaccine and an orthopoxvirus vaccine.
• People, particularly adolescent or young adult males, who are recommended to receive both vaccines might consider waiting 4 weeks between vaccines. This is because of the observed risk for myocarditis and pericarditis after receipt of ACAM2000 orthopoxvirus vaccine and COVID-19 vaccines, and the hypothetical risk for myocarditis and pericarditis after JYNNEOS vaccine. However, if a patient’s risk for mpox or severe disease due to COVID-19 is increased, administration of mpox and COVID-19 vaccines should not be delayed.

Nirsevimab: In accordance with General Best Practice Guidelines for Immunization, simultaneous administration of COVID-19 vaccine and nirsevimab (a long-acting monoclonal antibody for certain infants and young children for prevention of RSV) is recommended.

For best practices for administering multiple injections, see ACIP General Best Practice Guidelines for Immunization and Epidemiology and Prevention of Vaccine-Preventable Diseases (Pink Book).

Children ages 6 months–4 years should receive all doses of COVID-19 vaccine from the same manufacturer; this includes children who are moderately or severely immunocompromised and those who are not. People ages 5 years and older who are moderately or severely immunocompromised should receive a 3-dose initial vaccination series using vaccines from the same manufacturer.

In the following exceptional situations, a different age-appropriate COVID-19 vaccine may be administered:

• Same vaccine not available
• Previous dose unknown
• Person would otherwise not complete the vaccination series
• Person starts but unable to complete a vaccination series with the same COVID-19 vaccine due to a contraindication

A Vaccine Adverse Event Reporting System (VAERS) report is not indicated for these exceptional situations.

For people who receive 1 Moderna and 1 Pfizer-BioNTech vaccine dose, complete the initial vaccination series as follows:

• Children ages 6 months–4 years who are not moderately or severely immunocompromised should follow a 3-dose schedule. A third dose of either updated (2023–2024 Formula) Moderna vaccine or updated (2023–2024 Formula) Pfizer-BioNTech vaccine should be administered at least 8 weeks after the second dose.
• People ages 6 months and older who are moderately or severely immunocompromised should follow the recommended 3-dose schedule. A third dose of either updated (2023–2024 Formula) Moderna vaccine or updated (2023–2024 Formula) Pfizer-BioNTech vaccine should be administered as follows:
  • Ages 6 months–4 years: at least 8 weeks after the second dose
  • Ages 5 years and older: at least 4 weeks after the second dose

The COVID vaccination schedules for People who are not moderately or severely immunocompromised and People who are moderately or severely immunocompromised should be consulted for age-specific information; see Appendix B for recommended actions following interchangeability-related COVID-19 vaccine administration errors or deviations.

Pre-vaccination 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. If antibody testing is done, vaccination should be completed as recommended regardless of the antibody test result.

Interpretation of SARS-CoV-2 test results in vaccinated people

Prior receipt of a COVID-19 vaccine will not affect the results of SARS-CoV-2 viral tests (nucleic acid amplification or antigen tests).

See also CDC COVID-19 health care professional, CDC COVID-19 laboratory, and FDA SARS-CoV-2 laboratory testing Web pages.

Providers should counsel COVID-19 vaccine recipients, parents, or guardians about expected local and systemic reactions.

• Local reactions include pain/tenderness, swelling, and erythema at the injection site.
• Systemic reactions include fever, fatigue/malaise, headache, chills, myalgia, arthralgia; among younger children, particularly those younger than age 3 years, systemic reactions also can include irritability/crying, sleepiness, and loss of appetite.

Localized axillary lymphadenopathy on the same side as the vaccinated arm or groin, if vaccination was in the thigh, has been observed following vaccination with Moderna, Novavax, and Pfizer-BioNTech COVID-19 vaccines (2). Infrequently, people who have received dermal fillers might experience temporary swelling at or near the site of filler injection (usually face or lips) following a dose of an mRNA COVID-19 vaccine.

Myocarditis and pericarditis: People receiving any COVID-19 vaccine, especially males ages 12–39 years, should be made aware of the rare risk of myocarditis and pericarditis following COVID-19 vaccination. Counseling should include the need to seek care if symptoms of myocarditis or pericarditis develop after vaccination, particularly in the week after vaccination. See COVID-19 vaccination and myocarditis and pericarditis for additional information.

Anaphylactic reactions: Anaphylactic reactions have been rarely reported following receipt of COVID-19 vaccines. For more information on the assessment and potential management of anaphylaxis, see Preparing for the Potential Management of Anaphylaxis after COVID-19 Vaccination.

For more information on patient counseling, see Vaccine Recipient Education.

Syncope (fainting) might occur in association with any injectable vaccine, especially in adolescents. In accordance with General Best Practice Guidelines for Immunization, vaccination providers, particularly when vaccinating adolescents, should consider observing vaccine recipients for 15 minutes after vaccination.

Additionally, to monitor for allergic reactions, providers should consider observing people with the following precautions to a previously administered COVID-19 vaccine type for 30 minutes if a subsequent dose of the same vaccine type is administered:

• History of a non-severe, immediate (onset less than 4 hours) allergic reaction after administration of a previous dose of one COVID-19 vaccine type
• History of a diagnosed non-severe allergy to a component of the COVID-19 vaccine

See Contraindications and precautions for more information.

CDC considers the conditions listed in Table 3 to be COVID-19 vaccination contraindications and precautions.

Table 3. Contraindications and precautions to COVID-19 vaccination

People with a contraindication to one COVID-19 vaccine type (Table 3) may receive the alternative COVID-19 vaccine type in the usual vaccination setting. Consultation with an allergist-immunologist is encouraged to provide expert evaluation of the original allergic reaction, and depending on the outcome of the evaluation, reassess if administration of additional doses of the same vaccine type may be possible.

People with an allergy-related precaution to one COVID-19 vaccine type (Table 3) may receive the alternative COVID-19 vaccine type in the usual vaccination setting. Vaccination with the same COVID-19 vaccine type may be considered on an individual basis; the same vaccine type should be administered in an appropriate setting and under the supervision of a health care provider experienced in the management of severe allergic reactions.  An observation period of 30 minutes post-vaccination should be considered. Referral to an allergist-immunologist should be considered.

Healthcare professionals and health departments may request a consultation from the Clinical Immunization Safety Assessment COVIDvax project for a complex COVID-19 vaccine safety question not readily addressed by CDC guidance.

Adverse events that occur in a recipient following administration of any licensed or authorized COVID-19 vaccine should be reported to VAERS including:

• Vaccine administration errors whether or not associated with an adverse event
• Serious adverse events, irrespective of attribution to vaccination
• Cases of Multisystem Inflammatory Syndrome (MIS) in adults and children
• Cases of myocarditis
• Cases of pericarditis
• Cases of COVID-19 that result in hospitalization or death

Reporting is also encouraged for any other clinically significant adverse event, even if it is uncertain whether the vaccine caused the event. Information on how to submit a report to VAERS is available at https://vaers.hhs.gov or by calling 1-800-822-7967.

In clinical trials of Moderna and Pfizer-BioNTech COVID-19 vaccines, types of post-vaccination reactions were generally similar. The most frequent reported reactions, by age group, follow below.

Older children, adolescents, and adults

• Local: Pain at the injection site, sometimes severe
• Systemic: Fatigue, headache, and myalgia

Overall, symptoms tended to be more frequent and severe following the second dose of vaccine and among adolescents and younger adults compared with older adults.

Younger children (ages 6 months–5 years)

• Local: Pain/tenderness at the injection site
• Systemic: Fatigue; in the youngest children (ages 6–23 months), irritability/crying and drowsiness/sleepiness

In all age groups, most systemic symptoms were mild to moderate in severity, typically began 1–2 days after vaccination, and resolved after 1–2 days.

Febrile seizures can occur in infants and young children ages 6 months–5 years with any condition that causes a fever (most common with high fevers), including COVID-19. Febrile seizures are uncommon after vaccination and were rare in mRNA COVID-19 vaccine clinical trials for infants and young children. In rare instances, administration of certain combination vaccines or more than one vaccine at the same clinic visit has been associated with an increased risk of febrile seizures in infants and young children. The impact of simultaneous administration of COVID-19 and routine vaccines on the risk of febrile seizures has not been specifically studied. CDC is monitoring for febrile seizures following COVID-19 vaccination in infants and young children.

See also COVID-19 vaccination and myocarditis and pericarditis and vaccine reactions and adverse events for Moderna and Pfizer-BioNTech mRNA COVID-19 vaccines.

In clinical trials of Novavax COVID-19 Vaccine, the most frequent reported vaccine reactions included:

• Local: Pain/tenderness, redness, and swelling at the injection site
• Systemic: Fatigue/malaise, headache, and muscle pain

Most symptoms were mild to moderate in severity and resolved within 1–3 days. Overall, symptoms were more frequent in people ages 12–64 years compared to people ages 65 years and older and more frequent after dose 2 than dose 1 of the primary series. Among adults ages 18 years and older who received the Novavax booster dose, symptoms were more frequently reported after the booster dose than dose 2 of the primary series.

See also COVID-19 vaccination and myocarditis and pericarditis and vaccine reactions and adverse events for Novavax COVID-19 Vaccine.

Cases of myocarditis and pericarditis have rarely been observed following receipt of COVID-19 vaccines used in the United States.

Evidence from multiple monitoring systems in the United States and globally support a causal association for mRNA COVID-19 vaccines (Moderna or Pfizer-BioNTech) and myocarditis and pericarditis. Cases have occurred most frequently in adolescent and young adult males within 7 days after receiving the second dose of an mRNA COVID-19 vaccine (Moderna and Pfizer-BioNTech); however, cases have also been observed in females and after other doses. Data from clinical trials of Novavax COVID-19 Vaccine and post-authorization vaccine safety monitoring suggest an increased risk of myocarditis and pericarditis following Novavax vaccination.

For mRNA COVID-19 vaccines and Novavax COVID-19 Vaccine:

• After reviewing available data, ACIP and CDC determined that the benefits of COVID-19 vaccination (e.g., prevention of COVID-19 and its severe outcomes) outweigh the rare risk of myocarditis and pericarditis in all populations recommended for vaccination.
• Extending the interval to 8 weeks between the first and second doses for some people might reduce the rare risk of vaccine-associated myocarditis and pericarditis; see Considerations for extended intervals for COVID-19 vaccination for more information.
• People, especially males ages 12–39 years, should be made aware of the rare risk of myocarditis and pericarditis following receipt of these vaccines and the benefit of COVID-19 vaccination in reducing the risk of severe outcomes from COVID-19, including the possibility of cardiac sequelae.
  • Counseling should include the need to seek care if symptoms of myocarditis or pericarditis, such as chest pain, shortness of breath, or palpitations develop after vaccination, particularly in the week after vaccination.
  • In younger children, symptoms of myocarditis might also include non-specific symptoms such as irritability, vomiting, poor feeding, tachypnea, or lethargy.

For people who have a history of myocarditis associated with MIS-C or MIS-A, see COVID-19 vaccination and MIS-C and MIS-A.

Myocarditis or pericarditis after a dose of COVID-19 vaccine

Development of myocarditis or pericarditis within 3 weeks after a dose of any COVID-19 vaccine is a precaution to a subsequent dose of any COVID-19 vaccine, and subsequent doses should generally be avoided. Experts advise that these people should:

• Generally not receive a subsequent dose of any COVID-19 vaccine
• If, after a risk assessment, the decision is made to administer a subsequent COVID-19 vaccine dose, wait until at least after their episode of myocarditis or pericarditis has resolved (resolution of symptoms, no evidence of ongoing heart inflammation or sequelae as determined by patient’s clinical team)

Considerations for subsequent COVID-19 vaccination might include:

• Myocarditis or pericarditis considered unrelated to vaccination (e.g., due to SARS-CoV-2 or other viruses)
• Personal risk of severe acute COVID-19 (e.g., age, underlying conditions)
• Timing of any immunomodulatory therapies; ACIP’s General Best Practice Guidelines for Immunization can be consulted for more information

History of myocarditis or pericarditis that occurred prior to COVID-19 vaccination or more than 3 weeks after a COVID-19 vaccine dose

People who have a history of myocarditis or pericarditis that occurred before COVID-19 vaccination or more than 3 weeks after a COVID-19 vaccine dose may receive any currently FDA-approved or FDA-authorized COVID-19 vaccine after the episode of myocarditis or pericarditis has completely resolved (i.e., resolution of symptoms, no evidence of ongoing heart inflammation or sequelae as determined by the person’s clinical team). This includes people who had myocarditis or pericarditis due to SARS-CoV-2 or other viruses.

History of other heart disease

People who have a history of other heart disease, including congenital heart disease and Kawasaki disease, may receive any currently FDA-approved or FDA-authorized COVID-19 vaccine.

People with a known or potential SARS-CoV-2 exposure may receive vaccine if they do not have symptoms consistent with COVID-19; however, people should follow CDC’s post-exposure guidance.

COVID-19 vaccines are not recommended for post-exposure prophylaxis.

COVID-19 vaccination is recommended for everyone ages 6 months and older, regardless of a history of symptomatic or asymptomatic SARS-CoV-2 infection, including people with prolonged post-COVID-19 symptoms.

People with known current SARS-CoV-2 infection should defer any COVID-19 vaccination at least until recovery from the acute illness (if symptoms were present) and criteria to discontinue isolation have been met.

People who recently had SARS-CoV-2 infection may consider delaying a COVID-19 vaccine dose by 3 months from symptom onset or positive test (if infection was asymptomatic). Studies have shown that increased time between infection and vaccination might result in an improved immune response to vaccination. Also, a low risk of reinfection has been observed in the weeks to months following infection. Individual factors such as risk of COVID-19 severe disease or characteristics of the predominant SARS-CoV-2 strain should be taken into account when determining whether to delay getting a COVID-19 vaccination after infection.

Viral testing to assess for acute SARS-CoV-2 infection or serologic testing to assess for prior infection is not recommended for the purpose of vaccine decision-making.

MIS-C is a rare but severe condition in children and adolescents infected with SARS-CoV-2. MIS-A, a similar condition in adults, is even rarer and less well characterized. Both include a dysregulated immune response to SARS-CoV-2 infection. The risk of recurrence of MIS following reinfection with SARS-CoV-2 is unknown. It is also unknown if COVID-19 vaccination can, in rare instances, contribute to an MIS-like illness.

Experts consider the benefits of COVID-19 vaccination for people with a history of MIS-C or MIS-A (i.e., a reduced risk of severe disease including potential recurrence of MIS-C after reinfection) to outweigh a theoretical risk of an MIS-like illness or the risk of myocarditis following COVID-19 vaccination for those who meet the following two recovery criteria:

1. Clinical recovery has been achieved, including return to baseline cardiac function; and
2. It has been at least 90 days after the diagnosis of MIS-C or MIS-A

COVID-19 vaccination may also be considered for people who had MIS-C or MIS-A and do not meet both criteria, at the discretion of their clinical care team. Experts view clinical recovery, including return to baseline cardiac function, as an important factor when considering COVID-19 vaccination. Additional factors, such as the risk of severe COVID-19 due to age or certain medical conditions, may also be considered.

The timing of COVID-19 vaccination in people with a history of MIS-C or MIS-A should take into consideration current or planned immunomodulatory therapies for treatment of MIS-C or MIS-A; see Considerations for timing of COVID-19 vaccination in relation to immunosuppressive therapies for more information.

Onset of MIS more than 60 days after most recent COVID-19 vaccine dose

Administration of a subsequent COVID-19 vaccine dose(s) should be considered for those who meet the two recovery criteria described in Considerations for initiating COVID-19 vaccination in people with a history of MIS-C or MIS-A.

Onset of MIS 60 days or fewer after most recent COVID-19 vaccine dose

For persons in this category who meet the recovery criteria, the decision whether or not to administer a subsequent COVID-19 vaccine dose(s) should be made on an individual basis by the MIS clinical care team and patient or parent or guardian. Subsequent COVID-19 vaccine dose(s) should especially be considered if there is strong evidence that the MIS-C or MIS-A was a complication of a recent SARS-CoV-2 infection.

Staying up to date with COVID-19 vaccinations is recommended for people who are pregnant, trying to get pregnant now, or who might become pregnant in the future, and people who are breastfeeding. A growing body of evidence on the safety and effectiveness of COVID-19 vaccination indicates that the benefits of vaccination outweigh any potential risks of COVID-19 vaccination during pregnancy. Maternal vaccination has also been shown to be safe and effective, and protects infants younger than age 6 months from severe COVID-19 and hospitalization.

Side effects can occur after COVID-19 vaccination in pregnant people, similar to those among non-pregnant people. Acetaminophen can be offered as an option for pregnant people experiencing fever (fever has been associated with adverse pregnancy outcomes) or other post-vaccination symptoms.

1. For intervals of 3 months or less, 28 days (4 weeks) is a “month.” For intervals of 4 months or longer, a month is a “calendar month.”  For age group ranges (e.g., 6 months–4 years, 5–11 years), a dash (–) should be read as “through” and the upper range includes that year through the last day before the birth date.
2. The Society of Breast Imaging (SBI) has developed Revised SBI Recommendations for the Management of Axillary Adenopathy in Patients with Recent COVID-19 Vaccination which includes considerations for patients and healthcare professionals in scheduling screening exams in relation to the administration of a COVID-19 vaccine.