Page last updated/reviewed 03/08/2023.
COVID-19 vaccines are safe and effective. Everyone ages 6 months and older are eligible to receive a COVID-19 vaccine for Pfizer-BioNTech (Pfizer) and Moderna, and ages 18 years and older for Janssen/Johnson & Johnson (J&J) and Novavax. Parental consent is required for all eligible minors to be vaccinated.
There are four approved or authorized vaccines in the United States:
- Pfizer-BioNTech and Moderna COVID-19 vaccines are mRNA vaccines.
- Novavax COVID-19 vaccine is a protein subunit vaccine.
- Johnson & Johnson’s Janssen (J&J/Janssen) COVID-19 vaccine is a viral vector vaccine and can be given in some situations.
These vaccines are given as a shot in the muscle of the upper arm or in the thigh of a young child. COVID-19 vaccine ingredients are considered safe for most people.
How do the COVID-19 vaccines work? The vaccines teach your body to recognize COVID-19, so it is prepared to fight the virus.
- Messenger RNA vaccines (mRNA), like Pfizer-BioNTech and Moderna, provide instructions for your body to build a small protein that looks like a piece of COVID-19. This protein helps your body recognize the virus if you become infected.
- Protein subunit vaccines, such as Novavax, include harmless proteins of the virus that cause COVID-19. This helps your body recognize the virus if you become infected.
- Viral vector vaccines, like Johnson & Johnson/Janssen, provide instructions to build the spike protein found on the surface of COVID-19. This type of vaccine uses a harmless strand of another virus to deliver the instructions.
How well do 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 only received the primary series.
- Updated COVID-19 boosters can help build up protection that has decreased since previous vaccination. The updated boosters provide added protection against the recent Omicron subvariants that are more contagious than the previous ones. The recent subvariants, BA.4 and BA.5, are very closely related to the original variant, Omicron, with very small differences between itself and the original variant.
Are COVID-19 vaccines safe?
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 U.S., and the billions of vaccines administered globally, demonstrates that they are safe and effective.
Are there side effects to the COVID-19 vaccine?
When you are vaccinated, there may be some mild side effects that go away in a day or two. Side effects are a sign that the vaccine is working. Side effects could include:
- Pain, redness, or swelling in the arm where you received the vaccine. You can apply a cool, wet washcloth to reduce pain.
- Mild flu-like symptoms, like tiredness, nausea, muscle aches, chills, headache, or fever. Drink plenty of fluids and rest to feel more comfortable.
What are booster doses?
A booster dose refers to a vaccine given after the primary series to boost protection which might have waned over time.
What is the difference between monovalent and bivalent boosters?
Previous boosters are called “monovalent” because they were designed to protect against the original (i.e. one) virus that causes COVID-19. Updated boosters are called “bivalent” because they protect against both (i.e. two viruses) the original virus and the Omicron variants that causes COVID-19. More recent variants of Omicron are also covered by the vaccine.
Severe allergic reactions to vaccines are rare but can happen.