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Safety considerations for mRNA COVID-19 vaccines: Moderna and Pfizer-BioNTech

In of Moderna and Pfizer-BioNTech COVID-19 vaccines, types of post-vaccination reactions were generally similar. However, the frequency of some reactions varied by age, vaccine manufacturer, and vaccine dose. The most frequent reported reactions, by age group, follow below.

People ages 12 years and older

• Local: Injection site pain; less commonly, injection site redness and swelling, and axillary swelling/tenderness

• Systemic: Fatigue, headache, myalgia, arthralgia, and chills; less commonly, fever and nausea/vomiting

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.

Children ages 6 months–11 years

• Local: Injection site pain/tenderness; less commonly, injection site redness and swelling, and axillary or groin swelling/tenderness
• Systemic:
  • Ages 6 months–4 years: Irritability/crying, drowsiness/sleepiness, and decreased/loss of appetite, particularly in children younger than age 3 years; less commonly, fever
  • Ages 5–11 years: Fatigue and headache; less commonly, myalgia, arthralgia, fever, chills, diarrhea, and nausea/vomiting

In all age groups, most symptoms were mild to moderate in severity, typically began 1–2 days after vaccination, and resolved after 1–3 days.

can be consulted for detailed information about post-vaccination reactions for Moderna and Pfizer-BioNTech COVID-19 vaccines.

Febrile seizures in infants and young children occur infrequently after any vaccination; one febrile seizure was reported among participants ages 6 months–23 months in . obÌåÓý postmarketing safety surveillance for mRNA COVID-19 vaccines has not identified a safety concern for febrile seizure in children ages 6 months–5 years. The potential impact of simultaneous administration of COVID-19 and routine vaccines on the risk of febrile seizures has not been specifically studied. obÌåÓý is continuing to monitor for febrile seizures following COVID-19 vaccination in infants and young children.

See also COVID-19 vaccination and myocarditis and pericarditis.

Safety considerations for Novavax COVID-19 Vaccine

In clinical trials of among people ages 12 years and older, the most frequent reported vaccine reactions included:

• Local: Pain/tenderness at the injection site; less commonly, redness and swelling
• Systemic: Fatigue/malaise, headache, and myalgia; less commonly, arthralgia, nausea/vomiting, and fever

In addition, lymphadenopathy was also reported to occur after Novavax vaccination in the clinical trials.

Most symptoms were mild to moderate in severity, had onset 1–3 days after vaccination, 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 initial vaccination series.

The can be consulted for detailed information about post-vaccination reactions for Novavax COVID-19 Vaccine.

See also COVID-19 vaccination and myocarditis and pericarditis.

COVID-19 vaccination and myocarditis and pericarditis

Considerations for COVID-19 vaccination

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 support a causal association for mRNA COVID-19 vaccines (Moderna or Pfizer-BioNTech) and myocarditis and pericarditis. 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 . Data from outside the United States 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, the Advisory Committee on Immunization Practices (ACIP) and obÌåÓý 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; the option for an extended interval between doses; 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 multisystem inflammatory syndrome in children (MIS-C) or multisystem inflammatory syndrome in adults (MIS-A), see COVID-19 vaccination and MIS-C and MIS-A.

Myocarditis or pericarditis within 3 weeks 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 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; General Best Practices for Immunization can be consulted for more information

Myocarditis or pericarditis before 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 Food and Drug Administration (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.