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COVID-19 vaccines: Get the facts

Coronavirus vaccine research Coronavirus vaccine challenges Pathways to develop and produce a COVID-19 vaccine The vaccine development timeline How to protect yourself and prevent COVID-19 infection Content What are the benefits of getting a COVID-19 vaccine? Should I get the COVID-19 vaccine even if I've already had COVID-19? What COVID-19 vaccines have been authorized or approved and how do they work? Can a COVID-19 vaccine give you COVID-19? What are the possible general side effects of a COVID-19 vaccine? What are the long-term side effects of the COVID-19 vaccines? Can COVID-19 vaccines affect the heart? What is the connection between the Janssen/Johnson & Johnson COVID-19 vaccine and Guillain-Barre syndrome? What are the symptoms of a blood clotting reaction to the Janssen/Johnson & Johnson COVID-19 vaccine? Do the COVID-19 vaccines protect against the COVID-19 variants? Are COVID-19 vaccines free? Can I get a COVID-19 vaccine if I have an existing health condition? Is it OK to take an over-the-counter pain medication before or after getting a COVID-19 vaccine? Is there anyone who should not get a COVID-19 vaccine? What are the signs of an allergic reaction to a COVID-19 vaccine? Can I get a COVID-19 vaccine if I have a history of allergic reactions? Can pregnant or breastfeeding women get the COVID-19 vaccine? Can a COVID-19 vaccine affect fertility or menstruation? What COVID-19 vaccine has been approved for kids? If children don’t frequently experience severe illness with COVID-19, why do they need a COVID-19 vaccine? How did the FDA determine the safety and effectiveness of the Pfizer-BioNTech COVID-19 vaccine for use in kids ages 12 through 15? Can I stop taking safety precautions after getting a COVID-19 vaccine? Can I still get COVID-19 after I’m vaccinated? Are COVID-19 vaccine additional doses or boosters recommended?

What COVID-19 vaccines have been authorized or approved and how do they work?

Currently, several COVID-19 vaccines are in clinical trials. The FDA continues to review the results of these trials before approving or authorizing COVID-19 vaccines for use. But because there is an urgent need for COVID-19 vaccines and the FDA's vaccine approval process can take months to years, the FDA first gave emergency use authorization to COVID-19 vaccines based on less data than is normally required. The data must show that the vaccines are safe and effective before the FDA can give emergency use authorization or approval. Vaccines with FDA emergency use authorization or approval include:

  • Pfizer-BioNTech COVID-19 vaccine. The FDA has approved the Pfizer-BioNTech COVID-19 vaccine, now called Comirnaty, to prevent COVID-19 in people age 16 and older. The FDA approved Comirnaty after data found the vaccine is safe and effective. The Pfizer-BioNTech COVID-19 vaccine is 91% effective in preventing the COVID-19 virus with symptoms in people age 16 and older.

    The vaccine is still under an emergency use authorization for children ages 12 through 15. The vaccine is 100% effective in preventing COVID-19 in children ages 12 through 15. It requires two injections given 21 days apart. The second dose can be given up to six weeks after the first dose, if needed.

  • Moderna COVID-19 vaccine. The Moderna COVID-19 vaccine is 94% effective in preventing COVID-19 with symptoms. This vaccine is authorized for people age 18 and older. It requires two injections given 28 days apart. The second dose can be given up to six weeks after the first dose, if needed.
  • Janssen/Johnson & Johnson COVID-19 vaccine. In clinical trials, this vaccine was 66% effective in preventing the COVID-19 virus with symptoms — as of 14 days after vaccination. The vaccine also was 85% effective at preventing severe disease with COVID-19 — at least 28 days after vaccination. This vaccine is authorized for people age 18 and older. It requires one injection. The FDA and the Centers for Disease Control and Prevention (CDC) have recommended that use of this vaccine continue in the U.S. because the benefits outweigh the risks. If you are given this vaccine, you should be educated about the possible risks and symptoms of a blood clotting problem.

Both the Pfizer-BioNTech and the Moderna COVID-19 vaccines use messenger RNA (mRNA). Coronaviruses have a spikelike structure on their surface called an S protein. COVID-19 mRNA vaccines give cells instructions for how to make a harmless piece of an S protein. After vaccination, your cells begin making the protein pieces and displaying them on cell surfaces. Your immune system will recognize the protein and begin building an immune response and making antibodies.

The Janssen/Johnson & Johnson COVID-19 vaccine is a vector vaccine. In this type of vaccine, material from the COVID-19 virus is inserted into a different kind of weakened live virus, such as an adenovirus. When the weakened virus (viral vector) gets into your cells, it delivers material from the COVID-19 virus that gives your cells instructions to make copies of the S protein. Once your cells display the S proteins on their surfaces, your immune system responds by creating antibodies and defensive white blood cells. If you become infected with the virus that causes COVID-19, the antibodies will fight the virus.

Viral vector vaccines can't cause you to become infected with the COVID-19 virus or the viral vector virus. Also, the material that's delivered doesn't become part of your DNA.

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