COVID-19 vaccines provide protection against COVID-19, the disease caused by infection with the SARS-CoV-2 virus. Vaccination is the most effective strategy to prevent severe illness and death from SARS-CoV-2 infection. From January 2021 to April 2022, when the Omicron variant was predominant, hospitalization rates were 10.5 times higher in unvaccinated people and 2.5 times higher in vaccinated people with no booster dose, respectively, compared with those who had received a booster dose (1).
There are multiple COVID-19 vaccines currently in use worldwide (see the UNICEF COVID-19 Vaccine Market Dashboard and WHO Coronavirus [COVID-19] Dashboard); this content includes only those vaccines currently in use in the United States.
In the United States, the updated 2023–2024 formulation of the following COVID-19 vaccines are in use:
CDC: Janssen (Johnson & Johnson) COVID-19 Vaccine).
For more information, see the CDC: Interim Clinical Considerations for Use of COVID-19 Vaccines in the United States, COVID-19 Advisory Committee on Immunization Practices Vaccine Recommendations, the FDA prescribing information for the Pfizer-BioNTech and Moderna vaccines, and the FDA fact sheets for Pfizer-BioNTech, Moderna, and Novavax.
(See also Overview of Immunization and COVID-19.)
Reference
1. Havers FP, Pham H, Taylor CA, et al: COVID-19-Associated Hospitalizations Among Vaccinated and Unvaccinated Adults 18 Years or Older in 13 US States, January 2021 to April 2022. JAMA Intern Med 182(10):1071-1081, 2022. doi:10.1001/jamainternmed.2022.4299
Preparations of 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.
Indications for COVID-19 Vaccine
Contraindications and Precautions for COVID-19 Vaccine
Contraindications for COVID-19 vaccines are
Severe allergic reaction after a previous dose of either vaccine
Severe allergic reaction to a vaccine component
Precautions for COVID-19 vaccines are
Acute anaphylactic reaction immediately after a dose
Immunocompromise, including due to immunosuppressant therapy
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 spike protein vaccine that myocarditis and pericarditis have been reported after doses of these vaccines, 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: Clinical Considerations: Myocarditis and Pericarditis after Receipt of COVID-19 Vaccines Among Adolescents and Young Adults.)
See also CDC: Selected Adverse Events Reported after COVID-19 Vaccination.
Dose and Administration of COVID-19 Vaccine
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 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.
Adverse Effects of COVID-19 Vaccine
The COVID-19 vaccines all have similar adverse effects.
Rare, severe allergic reactions, including anaphylaxis, have been reported.
Other adverse effects are common:
Injection site pain, swelling, and redness
Fatigue
Headache
Muscle and joint pains
Fever and chills
Nausea
Malaise
Lymphadenopathy
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).
More Information
The following English-language resources may be useful. Please note that THE MANUAL is not responsible for the content of these resources.
Centers for Disease Control and Prevention (CDC): Use of COVID-19 Vaccines in the United States
Advisory Committee on Immunization Practices (ACIP): COVID-19 ACIP Vaccine Recommendations
European Centre for Disease Prevention and Control (ECDC): Coronavirus Disease (COVID-19): Recommended vaccinations
