COVID-19 vaccines: Get the facts

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

Currently, several COVID-19 vaccines are in clinical trials. The FDA will review the results of these trials before approving 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 will first be giving 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. Vaccines with FDA emergency use authorization include:

  • Pfizer-BioNTech COVID-19 vaccine. The Pfizer-BioNTech COVID-19 vaccine is 95% effective in preventing the COVID-19 virus with symptoms in people age 16 and older. The vaccine is 100% effective in preventing the COVID-19 virus in children ages 12 through 15. This vaccine is for people age 12 and older. 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 the COVID-19 virus with symptoms. This vaccine is 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 the COVID-19 virus — at least 28 days after vaccination. This vaccine is 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 that the protein doesn’t belong there 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, genetic 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 genetic 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 COVID-19 virus, 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 genetic material that’s delivered doesn’t become part of your DNA.

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