COVID-19 Vaccine

There are two mRNA vaccines for COVID-19:

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 one spike protein vaccine for COVID-19:

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

The BNT162b2 vaccine has FDA approval for the prevention of COVID-19 in people 16 years of age and older and EUA for people 6 months to 15 years of age.

The mRNA-1273 vaccine has FDA approval for people 18 years of age and older and EUA for people 6 months to 17 years of age.

The NVX-CoV2373 vaccine has EUA for people 12 years of age and older.

Contraindications for COVID-19 vaccines are

Precautions for COVID-19 vaccines are

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 given. 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.

A warning has been issued from the FDA for the mRNA vaccines and the adjuvanted vaccine that myocarditis Myocarditis Myocarditis is inflammation of the myocardium with necrosis of cardiac myocytes. Myocarditis may be caused by many disorders (eg, infection, cardiotoxins, drugs, and systemic disorders such... read more and pericarditis Pericarditis Pericarditis is inflammation of the pericardium, often with fluid accumulation in the pericardial space. Pericarditis may be caused by many disorders (eg, infection, myocardial infarction, trauma... read more have been reported after doses of these vaccines, particularly within 7 days of the second dose, suggesting there may be an increased risk of these events after vaccination (see FDA information for the vaccine produced by Pfizer-BioNTech, the vaccine produced by Moderna, and the vaccine produced by Novavax). The observed risk is highest in young males. Vaccine recipients should seek medical attention right away if they have chest pain, shortness of breath, or feelings of having a fast-beating, fluttering, or pounding heart after vaccination. Although some people have required intensive care, data from short-term follow-up studies suggest that symptoms usually resolved with conservative management.

See also CDC: Selected Adverse Events Reported after COVID-19 Vaccination.

For COVID-19 vaccinations available for use in the United States, all dose and administration information, including for primary series and recommended booster doses for all age groups and people with special conditions, is available from the CDC at Interim Clinical Considerations for Use of COVID-19 Vaccines Currently Approved or Authorized in the United States.

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

In 2022, the FDA amended the EUA for the mRNA vaccines to authorize bivalent formulations of the vaccines for use as a single booster dose (see the FDA fact sheet). The bivalent vaccines (referred to as updated boosters) contain two mRNA components of the SARS-CoV-2 virus. One component is the original strain of SARS-CoV-2, and the other one targets the most recent Omicron subvariants known as BA.4 and BA.5. Since the introduction of the bivalent vaccines, the CDC authorizes use of only the updated bivalent vaccine as a booster. The original (monovalent) mRNA booster is no longer available.

A booster dose of the recombinant spike protein nanoparticle vaccine produced by Novavax (instead of a bivalent mRNA booster dose) may be used in limited situations in people ages 18 years and older who completed any FDA-approved or FDA-authorized monovalent primary series, have not received any previous booster dose(s), and are unable or unwilling to receive an mRNA vaccine and would otherwise not receive a booster dose.

The COVID-19 vaccines all have similar adverse effects. (See CDC: Possible Side Effects After Getting a COVID-19 Vaccine.)

Rare, severe allergic reactions, including anaphylaxis Anaphylaxis Anaphylaxis is an acute, potentially life-threatening, IgE-mediated allergic reaction that occurs in previously sensitized people when they are reexposed to the sensitizing antigen. Symptoms... read more , have been reported.

Other adverse effects are common:

Adverse effects typically last several days.

Reactive lymphadenopathy may occur after COVID-19 vaccination and may result in a false-positive reading on mammography. Multiple studies have been done, and the most recent recommendation from the Society of Breast Imaging, released in February 2022, recommends no delay between COVID vaccination and screening mammogram (see Society of Breast Imaging: 2022 Position Statements and Recommendations: Revised SBI Recommendations for the Management of Axillary Adenopathy in Patients with Recent COVID-19 Vaccination).

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