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How do COVID-19 vaccines work?

Last Updated: 12/29/2020

Vaccines work by triggering a person's immune system to develop protection against a disease.

COVID-19 vaccines help our bodies develop immunity to the virus that causes COVID-19 without us having to get the illness. Different types of vaccines work in different ways to offer protection.

Both of the vaccines that have received an FDA Emergency Use Authorization to date are messenger RNA vaccines (mRNA). Unlike many other vaccines which put a weakened or inactivated germ into our bodies, mRNA vaccines when injected instruct our cells how to make a protein—or even just a piece of a protein—that triggers an immune response inside our bodies. That immune response, which produces antibodies, is what protects us from getting infected if the real virus enters our bodies.

This is the first time that mRNA vaccines have received Emergency Use Authorization or been distributed to the public, but researchers have been studying and working with mRNA vaccines for decades. Interest has grown in these vaccines because they can be developed in a laboratory using readily available materials. This means the process can be standardized and scaled up, making vaccine development and production faster than traditional methods of making vaccines.

As soon as the necessary information about the virus that causes COVID-19 was available, scientists began designing the mRNA vaccine for cells to build the unique spike protein into an mRNA vaccine.

For more of how COVID-19 mRNA vaccines work, visit this CDC page. Additional information on other COVID-19 vaccines that are or soon will be undergoing large-scale (Phase 3) clinical trials in the United States can be found here.

What to Know About Available COVID-19 Vaccines

COVID-19 vaccines that are authorized for use have gone through clinical trials involving tens of thousands of participants to determine their safety and efficacy.

The U.S. Food and Drug Administration has issued Emergency Use Authorizations for the Pfizer-BioNTech COVID-19 vaccine and the Moderna vaccines.

For the Pfizer-BioNTech vaccine, please consult these FDA fact sheets:

For the Moderna vaccine, please consult these FDA fact sheets:

Both vaccines are given as an injection into the muscle and as a series of two shots. The Pfizer-BioNTech vaccine is two doses given 21 days apart and the Moderna vaccine is two doses given 28 days apart.

COVID-19 vaccines will not give you COVID-19. None of the COVID-19 vaccines currently in development use the live virus that causes COVID-19.

COVID-19 vaccines will not cause you to test positive on COVID-19 viral tests. Vaccines won't cause you to test positive on viral tests, which are used to see if you have a current infection.

People who have gotten sick with COVID-19 may still benefit from getting vaccinated. At this time, experts do not know how long until someone is protected from getting sick again after recovering from COVID-19. The immunity someone gains from having an infection (natural immunity) varies from person to person. Some early evidence suggest natural immunity may not last very long. Although there is no minimal interval between infection and vaccination, current evidence suggests reinfection is uncommon in the 90 days after initial infection, and thus persons with documented acute infection in the preceding 90 days may defer vaccination until the end of this period, if desired.

Getting vaccinated can help prevent getting sick with COVID-19. There is no way to know how COVID-19 will affect you. If you get sick, you also may spread the disease to friends, family, and others around you while you are sick. COVID-19 vaccination helps protect you by creating an immune response without having to experience sickness.

Receiving an mRNA vaccine will not alter your DNA. mRNA (messenger ribonucleic acid) can most easily be described as instructions for how to make a protein or even just a piece of a protein. mRNA is not able to alter or modify a person's genetic makeup (DNA).

Sources: NJ DOH COVID-19 Vaccine FAQs, NJ DOH COVID-19 Vaccines - Know the Facts, CDC; https://www.state.nj.us/health/cd/documents/topics/NCOV/Public_FAQ.pdf