Overview of COVID-19 Vaccines

What You Need to Know
  • There are two types of COVID-19 vaccines available in the United States: mRNA vaccines and protein subunit vaccines.
  • CDC recommends the 2023–2024 updated COVID-19 vaccines: Pfizer-BioNTech, Moderna, or Novavax, to protect against serious illness from COVID-19.
  • Vaccine recommendations are based on age, and in some cases, time since last dose, the first vaccine received, and immunocompromised status.
  • Side effects after a COVID-19 vaccine are common, however severe allergic reactions after getting a COVID-19 vaccine are rare.

Types of COVID-19 Vaccines

COVID-19 vaccine vials

There are two types of COVID-19 vaccines licensed or authorized in the United States. None of the COVID-19 vaccines are preferred over another when more than one licensed or authorized, recommended, and age-appropriate vaccine is available.

mRNA COVID-19 vaccines

Pfizer-BioNTech and Moderna COVID-19 vaccines are mRNA vaccines. mRNA vaccines use mRNA created in a laboratory to teach our cells how to make a protein—or even just a piece of a protein—that triggers an immune response inside our bodies. The mRNA from the vaccines is broken down within a few days after vaccination and discarded from the body.

As of September 12, 2023, the 2023–2024 updated Pfizer-BioNTech and Moderna COVID-19 vaccines were recommended by CDC for use in the United States.

Protein subunit COVID-19 vaccines

Novavax COVID-19 vaccine is a protein subunit vaccine. Protein subunit vaccines contain pieces (proteins) of the virus that causes COVID-19. The virus pieces are the spike protein. The Novavax COVID-19 vaccine contains another ingredient called an adjuvant. It helps the immune system respond to that spike protein. After learning how to respond to the spike protein, the immune system will be able to respond quickly to the actual virus spike protein and protect you against COVID-19.

As of October 3, 2023, the 2023-2024 updated Novavax COVID-19 Vaccine, Adjuvanted was recommended by CDC for use in the United States for people aged 12 years and older.

Composition and Ingredients

The 2023–2024 updated COVID-19 vaccines more closely targets the XBB lineage of the Omicron variant and could restore protection against severe COVID-19 that may have decreased over time.

The manufacturers use different ingredients in the vaccines. None of the vaccines contain eggs, gelatin, latex, or preservatives. After the body produces an immune response, it discards all of the vaccine ingredients, just as it would discard any substance that cells no longer need. This process is a part of normal body functioning.

Find a full list of ingredients and information on the conditions of use, storage and handling, preparation, and administration procedures in the COVID-19 vaccine-specific package inserts and FDA fact sheets and U.S. COVID-19 Vaccine Product Information.

None of the COVID-19 vaccines affect or interact with our DNA and the following are not included in the vaccines:

  • No preservatives such as thimerosal or mercury or any other preservatives.
  • No antibiotics such as sulfonamide or any other antibiotics.
  • No medicines or therapeutics such as ivermectin or any other medications.
  • No tissues such as aborted fetal cells, gelatin, or any materials from any animal.
  • No food proteins such as eggs or egg products, gluten, peanuts, tree nuts, nut products, or any nut byproducts. (COVID-19 vaccines are not manufactured in facilities that produce food products).
  • No metals such as iron, nickel, cobalt, titanium, or rare earth alloys. They also do not have any manufactured products like microelectronics, electrodes, carbon nanotubes or other nanostructures, or nanowire semiconductors.
  • No latex. The vial stoppers used to hold the vaccine also do not contain latex.

Dosage and Administration

CDC recommends that people receive the age-appropriate COVID-19 vaccine product and dosage based on their age on the day of vaccination. COVID-19 vaccine dose amounts are different for different age groups. COVID-19 vaccine doses and timing are different for people who are moderately or severely immunocompromised.

These vaccines are given by the intramuscular route, which means they are given as a shot in the muscle of the upper arm or in the thigh of a young child.

How Well COVID-19 Vaccines Work

  • People who are up to date have lower risk of severe illness, hospitalization and death from COVID-19 than people who are unvaccinated or who have not completed the doses recommended for them by CDC.
  • Additional updated COVID-19 vaccine doses can help restore protection that has decreased since previous vaccination.
  • CDC will continue to provide updates as we learn more.

Safety of COVID-19 Vaccines

COVID-19 vaccines have undergone—and will continue to undergo—the most intensive safety monitoring in U.S. history. Evidence from the hundreds of millions of COVID-19 vaccines already administered in the United States, and the billions of vaccines administered globally, demonstrates that they are safe and effective.

Side Effects

  • Side effects that happen within 7 days of getting vaccinated are common but are mostly mild. Sometimes they may affect a person’s ability to do daily activities.
  • Side effects throughout the body (such as fever, chills, tiredness, and headache) are more common after the second dose of a Pfizer-BioNTech, Moderna, or Novavax COVID-19 vaccine.

Adverse Events

  • Severe allergic reactions to all vaccines are rare but can happen.
  • There is a rare risk of myocarditis and pericarditis associated with mRNA COVID-19 vaccination, mostly among males ages 12–39 years. The rare risk may be further reduced with a longer interval between the first and second dose.
  • Cases of myocarditis and pericarditis have also been reported in people who received Novavax COVID-19 vaccine.
  • CDC continues to investigate long-term effects of myocarditis. Initial findings show nearly all patients have recovered.

Learn more about vaccine safety monitoring after a vaccine is authorized or approved for use.

If You Are Allergic to an Ingredient in a COVID-19 Vaccine or Had a Previous Severe Allergic Reaction

  • If in the past you have had a severe allergic reaction to an ingredient in an COVID-19 vaccine or if you have a known allergy to an ingredient in a COVID-19 vaccine, you should not get that COVID-19 vaccine. Examples:
    • If you are allergic to polyethylene glycol (PEG), you should not get Pfizer-BioNTech or Moderna COVID-19 vaccines.
    • If you are allergic to polysorbate, you should not get Novavax COVID-19 vaccines.
  • If you aren’t able to get one type of COVID-19 vaccine, talk to your doctor about your options for getting a different type of COVID-19 vaccine.
Learn About Getting Your Vaccine
  • How can you prepare for vaccination?
  • What can you expect during and after your vaccination?
  • Uninsured? You can still get a free COVID-19 vaccine. Learn more about CDC’s Bridge Access program.
Getting Your COVID-19 Vaccine
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