COVID-19 Vaccine

There are 2 SARS-CoV-2 virus (COVID-19) mRNA vaccines for COVID-19 used in the United States.There are 2 SARS-CoV-2 virus (COVID-19) mRNA vaccines for COVID-19 used in the United States.

The mRNA vaccines do not contain viral antigen but rather deliver a small, synthetic piece of mRNA that encodes for the desired target antigen (the spike protein). After being taken up by cells of the immune system, the vaccine mRNA degrades after instructing the cell to produce viral antigen. The antigen is then released and triggers the desired immune response to prevent severe infection upon subsequent exposure to the actual virus.

There is 1 SARS-CoV-2 virus (COVID-19) recombinant spike protein nanoparticle vaccine for COVID-19 used in the United States.There is 1 SARS-CoV-2 virus (COVID-19) recombinant spike protein nanoparticle vaccine for COVID-19 used in the United States.

The spike protein vaccine contains a recombinant form of the SARS-CoV-2 spike protein, which then triggers the desired immune response.

The mRNA vaccines are indicated for the prevention of infection caused by SARS-CoV-2 virus in people ≥ 12 years of age and are authorized for emergency use in people ≥ 6 months of age.

The recombinant spike protein nanoparticle vaccine is indicated for the prevention of infection caused by SARS-CoV-2 virus in people ≥ 12 years of age.

Adults ≥ 65 years of age should receive 2 doses of the latest COVID-19 vaccine formulations 6 months apart. People ≥ 6 months of age with moderate or severe immunocompromise should also receive ≥ 2 doses to protect against severe COVID-19 infection (1, 2).

Contraindications for COVID-19 vaccines are the following:

• Severe allergic reaction after a previous dose of any vaccine

• Severe allergic reaction to a vaccine component

Precautions for COVID-19 vaccines include the following:

• Acute anaphylactic reaction immediately after a dose

• Immunocompromise, including due to immunosuppressant therapy

• Moderate or severe illness, with or without fever

• History of multisystem inflammatory syndrome in children (MIS-C) or multisystem inflammatory syndrome in adults (MIS-A)

• History of myocarditis or pericarditis within 3 weeks after a dose of any COVID-19 vaccine

Appropriate medical treatment to manage immediate allergic reactions must be immediately available in the event an acute anaphylactic reaction occurs after any COVID-19 vaccine is administered. COVID-19 vaccine recipients should be monitored for immediate adverse reactions.

Immunocompromised people, including those receiving immunosuppressant therapy, may have a diminished immune response to these vaccines. (See also CDC: Interim Clinical Considerations for Use of COVID-19 Vaccines in the United States.)

The U.S. Food and Drug Administration (FDA) has issued a warning regarding reports of myocarditis and pericarditis after administration of COVID-19 vaccines, suggesting there may be an increased risk of these events after vaccination (1). The observed risk is highest in young males. Vaccine recipients should seek medical attention right away if they have chest pain, dyspnea, tachycardia, or palpitations after vaccination. Although some people have required intensive care, data from short-term follow-up studies suggest that symptoms usually resolved with conservative management.

For COVID-19 vaccinations available for use in the United States, all dose and administration information for all age groups and people with special conditions is available from the CDC (1).

COVID-19 vaccine doses should be administered by the intramuscular route.

The COVID-19 vaccines all have similar adverse effects.

Rare, severe allergic reactions, including anaphylaxis, have been reported.

Other adverse effects are common and may include:

• Injection site pain, swelling, and erythema

• Fatigue

• Headache

• Muscle and joint pains

• Fever and chills

• Nausea and vomiting

• Malaise

• Lymphadenopathy

Adverse effects tend to last for several days.

Reactive lymphadenopathy may occur after COVID-19 vaccination and may result in a false-positive reading on mammography (1). Multiple studies have been performed, and routine screening mammography should not be delayed after COVID vaccination (2, 3).

For more information about adverse effects of these vaccines, refer to the prescribing information.

The following English-language resources may be useful. Please note that The Manual is not responsible for the content of these resources.

1. Centers for Disease Control and Prevention (CDC): Interim Clinical Considerations for Use of COVID-19 Vaccines in the United States

2. CDC: Coronavirus Disease 2019 (COVID-19) Vaccine Safety

3. Advisory Committee on Immunization Practices (ACIP): ACIP Recommendations: COVID-19 Vaccine

4. ACIP: Changes in the 2025 Adult Immunization Schedule

5. ACIP: Changes in the 2025 Child and Adolescent Immunization Schedule

6. European Centre for Disease Prevention and Control (ECDC): Coronavirus Disease (COVID-19): Recommended vaccinations