Implementation Guidance

Transitioning from a younger to older age group

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 children who transition from age 4 years to age 5 years and children who are moderately or severely immunocompromised and transition from age 11 years to age 12 years, the option to administer a lower dosage is no longer authorized (see Table 1 and Table 2).

Simultaneous administration of COVID-19 vaccines with other vaccines

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.

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: Simultaneous administration of COVID-19 vaccine and nirsevimab (a long-acting monoclonal antibody indicated for certain infants and young children for prevention of respiratory syncytial virus (RSV) lower respiratory tract disease) is recommended.

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

Interchangeability of COVID-19 vaccines

Administration of COVID-19 vaccine doses from different manufacturers

COVID-19 vaccine doses from the same manufacturer should be administered whenever recommended. In the following circumstances, an age-appropriate COVID-19 vaccine from a different manufacturer may be administered:

• Same vaccine not available at the time of the clinic visit
• Previous dose unknown
• Person would otherwise not receive a recommended vaccine dose
• 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 in these circumstances.

mRNA COVID-19 vaccines

If mRNA vaccine doses are administered from different manufacturers because of a circumstance described above, a 3-dose schedule for initial vaccination should be followed:

Children ages 6 months–4 years

• The second dose is administered 4–8 weeks after the first dose.
• The third dose of either 2024–2025 Moderna vaccine or 2024–2025 Pfizer-BioNTech vaccine is administered at least 8 weeks after the second dose.

People ages 6 months and older who are moderately or severely immunocompromised

• The second dose is administered 4 weeks after the first dose.
• The third dose of either 2024–2025 Moderna vaccine or 2024–2025 Pfizer-BioNTech vaccine is 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

Novavax COVID-19 vaccine

People ages 12 years and older who are initiating vaccination with Novavax COVID-19 Vaccine (i.e., previously unvaccinated) and receive a first dose of Novavax should complete the 2-dose initial vaccination series with Novavax vaccine. However, if more than 8 weeks have elapsed since receipt of the first dose of Novavax, any 2024–2025 COVID-19 vaccine (i.e., Moderna, Novavax, or Pfizer-BioNTech) may be administered under routine vaccination.

See the Appendix for additional information if doses from different manufacturers are administered for initial vaccination.

COVID-19 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 SARS-CoV2 infection. If antibody testing is done, vaccination should proceed as recommended regardless of the antibody test result.

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

For more information see Overview of Testing for SARS-CoV-2 and the Food and Drug Administration web page on serologic testing.

Pre-vaccination counseling

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

• Local reactions include pain/tenderness, and, less commonly, swelling and redness at the injection site.
• Systemic reactions include fever, fatigue/malaise, headache, chills, myalgia, arthralgia, and diarrhea; 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. 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 and the option for an extended interval between doses. 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.

Post-vaccination observation period

Syncope (fainting) might occur in association with any injectable vaccine, especially in adolescents. In accordance with General Best Practices 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 Considerations for people with a history of allergies or allergic reactions for more information.