Vaccines to prevent coronavirus disease 2019 (COVID-19) are perhaps the best hope for ending the pandemic. But as the U.S. Food and Drug Administration (FDA) continues approving or authorizing emergency use of COVID-19 vaccines, you likely have questions. Find out about the benefits of the COVID-19 vaccines, how they work, the possible side effects and the importance of continuing to take infection prevention steps.
A COVID-19 vaccine might:
Getting COVID-19 might offer some natural protection or immunity from reinfection with the virus that causes COVID-19. But it’s not clear how long this protection lasts. Because reinfection is possible and COVID-19 can cause severe medical complications, it’s recommended that people who have already had COVID-19 get a COVID-19 vaccine. If you were treated for COVID-19 with monoclonal antibodies or convalescent plasma, wait 90 days before getting a COVID-19 vaccine.
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.
No. The COVID-19 vaccines currently being developed in the U.S. don't use the live virus that causes COVID-19. As a result, the COVID-19 vaccines can't cause you to become sick with COVID-19 or shed any vaccine components.
Keep in mind that it will take a few weeks for your body to build immunity after getting a COVID-19 vaccination. As a result, it's possible that you could become infected with the virus that causes COVID-19 just before or after being vaccinated.
A COVID-19 vaccine can cause mild side effects after the first or second dose, including:
You'll be monitored for 15 minutes after getting a COVID-19 vaccine to see if you have an allergic reaction. Most side effects go away in a few days. Side effects after the second dose might be more intense. Many people have no side effects.
A COVID-19 vaccine may cause side effects similar to signs and symptoms of COVID-19. If you've been exposed to COVID-19 and you develop symptoms more than three days after getting vaccinated or the symptoms last more than two days, self-isolate and get tested.
©1998-2021 Mayo Foundation for Medical Education and Research (MFMER). All rights reserved. Terms of Use.
We would love to speak with you about our goals for the future of healthcare.