Ask the Experts: COVID-19: Vaccine Safety

Results (13)

Recipients of mRNA COVID-19 vaccines often experience local (e.g., pain, swelling, redness at the injection site, localized swollen lymph nodes in the armpit of the vaccinated arm) or systemic (e.g., fever, fatigue, headache, chills, body and joint aches) post-vaccination symptoms. Most systemic post-vaccination symptoms are mild to moderate in severity, occur within the first three days of vaccination, and resolve within 1–3 days of onset.

Among children ages 6 months through 4 years pain or tenderness at the injection site was the most frequent local reaction noted in clinical trials. The most common systemic symptom in older children was fatigue; in younger children (ages 6 through 23 months), irritability/crying and drowsiness/sleepiness were most common. Most systemic symptoms were mild to moderate in severity, typically began 1 to 2 days after vaccination, and resolved after 1 to 2 days.

Last reviewed: November 16, 2025

In clinical trials of the COVID-19 adjuvanted protein vaccine, known commercially as Nuvaxovid (Sanofi-Novavax), pain or tenderness at the injection site was the most frequently reported local reaction among vaccine recipients; redness and swelling were reported less frequently. Fatigue, headache, and muscle pain were the most commonly reported systemic reactions. Most symptoms were mild to moderate in severity and resolved within 1 to 3 days. Overall, symptoms were more frequent in people ages 18 through 64 years compared to people ages 65 years and older.

Last reviewed: November 16, 2025

Any current FDA-licensed COVID-19 vaccine may be given to individuals with a history of GBS.

Last reviewed: November 16, 2025

There is no evidence that any of the COVID-19 vaccines affect current or future fertility.

Last reviewed: November 16, 2025


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Last reviewed: November 16, 2025

There is a 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. Despite this risk, evaluation conducted in past seasons demonstrated that the benefits of vaccination clearly outweigh the risks in all age groups. SARS-CoV-2 virus infection poses a substantially higher risk of myocarditis or pericarditis than COVID-19 vaccination.

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. For the 2025–2026 formulations, an initial series is no longer recommended except in infants and toddlers younger than age 2 years or in people with moderate or severe immunocompromise. These groups have not historically been associated with an increased risk of pericarditis or myocarditis following COVID-19 vaccination. Extending the interval between doses to 8 weeks in infants and toddlers may reduce the rare risk of myocarditis following the second dose; 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 completely recovering from their acute symptoms. Post-vaccination myocarditis is milder than myocarditis following viral infection. CDC continues to assess long-term outcomes in people with myocarditis after mRNA COVID-19 vaccination.

People who receive COVID-19 vaccines, especially males age 12 through 39, should 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#cdc_vaccine_special_topics_research-covid-19-vaccination-and-myocarditis-and-pericarditis.

CDC also has published additional clinical considerations for the evaluation and care of patients with myocarditis or pericarditis following mRNA vaccination: www.cdc.gov/vaccines/covid-19/clinical-considerations/myocarditis.html.

Last reviewed: November 16, 2025

Serious allergic reactions, such as anaphylaxis, in the minutes following vaccination are rare but are possible with any vaccine. Every vaccination site should have staff available who are trained and equipped to recognize and respond to signs of anaphylaxis in a vaccine recipient. See this CDC website for additional information about preparing for the management of anaphylaxis following COVID-19 vaccination: www.cdc.gov/vaccines/covid-19/clinical-considerations/managing-anaphylaxis.html?anaphylaxis-management.html.

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 any mRNA COVID-19 vaccine is a contraindication to vaccination with all mRNA COVID-19 vaccine formulations; however, such a reaction is generally a precaution (not a contraindication) to the use of the adjuvanted protein subunit vaccine (Nuvaxovid, Sanofi-Novavax). The CDC’s COVID-19 interim clinical considerations section on contraindications and precautions for details: www.cdc.gov/covid/hcp/vaccine-considerations/contraindications-precautions.html#cdc_vaccine_special_topics_research-considerations-for-people-with-a-history-of-allergies-or-allergic-reactions.

Last reviewed: November 16, 2025

In accordance with general best practices for vaccination, all people should be observed for at least 15 minutes after vaccination for signs of an immediate allergic reaction.

If you vaccinate a person who has an allergy-related precaution to COVID-19 vaccination with the same type of COVID-19 vaccine associated with the precaution, you should consider a 30-minute observation period following vaccination. See CDC’s detailed considerations for people with a history of allergies or allergic reactions: www.cdc.gov/covid/hcp/vaccine-considerations/contraindications-precautions.html#cdc_vaccine_special_topics_research-considerations-for-people-with-a-history-of-allergies-or-allergic-reactions.

Last reviewed: November 16, 2025

For all licensed COVID-19 vaccines (Moderna [mNexspike, Spikevax], Sanofi-Novavax [Nuvaxovid], Pfizer-BioNTech [Comirnaty]) healthcare providers are strongly encouraged to report to the Vaccine Adverse Event Reporting System (VAERS) the following:

  • Any adverse event that occurs after the administration of a vaccine licensed in the United States, whether or not it is clear that a vaccine caused the adverse event
  • Vaccine administration errors, whether or not associated with an adverse event

Information on how to submit a report to VAERS is available at https://vaers.hhs.gov or by calling 1-800-822-7967.

Last reviewed: November 16, 2025

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.

Last reviewed: November 16, 2025

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.

Last reviewed: November 16, 2025

No. COVID-19 vaccines are not currently part of the VICP, although a transition to the VICP is anticipated in the future. 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.

Last reviewed: November 16, 2025

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