Ask the Experts: COVID-19

The COVID-19 questions were last reviewed on November 16, 2025. See CDC’s Use of COVID-19 Vaccines in the United States Interim Clinical Considerations for more information. To keep up with the current available COVID-19 resources from CDC, FDA, and Immunize.org, see Immunize.org’s Checklist of Current Versions of U.S. COVID-19 Vaccine Guidance and Clinic Support Tools, updated at least monthly. For alerts about new Immunize.org or CDC COVID-19 resources, subscribe to our weekly e-newsletter, IZ Express.

Results (86)

The COVID-19 vaccines currently available in the United States (mRNA vaccines and the Nuvaxovid adjuvanted protein vaccine) are not contraindicated in patients with a history of TTS. The Janssen COVID-19 vaccine associated with immune-mediated TTS in the United States had not been available in the United States since 2023.

Last reviewed: November 16, 2025

According to CDC, MIS-C and MIS-A both include a dysregulated immune response to SARS-CoV-2 infection. Experts consider the benefits of vaccination to outweigh the theoretical risk of an MIS-like illness or the risk of myocarditis following COVID-19 vaccination in a person with a history of MIS-C or MIS-A if the person meets the following criteria: (1) they have clinically recovered, including return to baseline cardiac function; and (2) it has been at least 90 days since the diagnosis of MIS-C or MIS-A.

There are additional considerations for vaccination of those who do not meet these criteria. Refer to CDC’s detailed guidance for the most current clinical considerations for vaccination of children and adults who have experienced this syndrome following SARS-CoV-2 infection or who have experienced MIS-like illness following COVID-19 vaccination: www.cdc.gov/covid/hcp/vaccine-considerations/special-situations-and-populations.html#cdc_clinical_guidance_recomm_key-covid-19-vaccination-and-mis-c-and-mis-a.

Last reviewed: November 16, 2025

CDC guidance is that people who have a history of completely resolved myocarditis or pericarditis unrelated to COVID-19 vaccination (e.g., due to SARS-CoV-2 or other viruses) may receive any age-appropriate COVID-19 vaccine. “Complete resolution” includes resolution of symptoms attributed to myocarditis or pericarditis, as well as no evidence of ongoing heart inflammation or sequelae as determined by the person’s clinical team.

For people who have a history of myocarditis associated with MIS-C or MIS-A following SARS-CoV-2 infection, see CDC’s interim clinical considerations concerning COVID-19 vaccination and MIS-C and MIS-A: www.cdc.gov/covid/hcp/vaccine-considerations/special-situations-and-populations.html#cdc_clinical_guidance_recomm_key-covid-19-vaccination-and-mis-c-and-mis-a.

Complete and current clinical considerations for COVID-19 vaccination of patients with a history of myocarditis are available from CDC here: www.cdc.gov/covid/hcp/vaccine-considerations/safety-considerations.html#cdc_vaccine_special_topics_research-covid-19-vaccination-and-myocarditis-and-pericarditis.

Last reviewed: November 16, 2025

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 experts advise that these people should generally not receive a subsequent dose of any COVID-19 vaccine. Under certain conditions, the clinical team may determine that benefits of vaccination outweigh risks, but vaccination should wait until at least their episode of myocarditis or pericarditis has resolved and there is no evidence of ongoing heart inflammation or sequelae. See CDC’s detailed guidance for additional information about these clinical considerations: www.cdc.gov/covid/hcp/vaccine-considerations/safety-considerations.html#cdc_vaccine_special_topics_research-covid-19-vaccination-and-myocarditis-and-pericarditis.

Last reviewed: November 16, 2025

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

Vaccinating people against influenza who have recently tested positive for COVID-19 involves multiple considerations, such as whether vaccinating them could expose others to COVID-19, how sick they are, their risk for severe influenza illness, the ability to vaccinate at a later date, and the desire to avoid confusing postvaccination symptoms with those of COVID-19. Usually, people who are known to be infectious should not be brought to a vaccination setting if doing so could expose others to COVID-19. Any moderate or severe acute illness is a precaution to influenza vaccination: vaccination should generally be deferred until recovery. For people with mild or asymptomatic COVID-19, delaying vaccination also might be considered to avoid confusing COVID-19 symptoms with postvaccination reactions.

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 (Novavax) COVID-19 vaccine 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

For details, refer to the specific vaccine’s package insert.

Immunize.org has assembled links to key COVID-19 vaccine resources, including package inserts, in the Checklist of Current Versions of U.S. COVID-19 Vaccination Guidance and Clinic Support Tools: www.immunize.org/catg.d/p3130.pdf.

Last reviewed: November 16, 2025

Although routine transportation of vaccines to different facilities is not generally recommended, there are times when this is necessary. CDC recommends transporting COVID-19 vaccine in unopened vials or manufacturer-filled syringes (MFS) and always with a continuous temperature monitoring device to ensure adherence to authorized storage times and temperatures. See the product package insert for details on permissible conditions for transport.

Last reviewed: November 16, 2025

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