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Vaccines work by mimicking the infectious bacteria or virus that causes disease to stimulate our immune systems and build up resistance.

UNC Health strongly recommends most people receive a COVID-19 vaccine when it becomes available—to protect themselves, their colleagues and families.

We know that you may have questions about COVID-19 vaccines, including how they works and if they are safe. It is important that each of us have all the information we need to protect ourselves and those around us – here are the facts.

How do vaccines work?

Vaccines expose the body to harmless molecules that mimic bacterial or viral infections so that our immune systems are triggered and we build resistance to actual infections.[1] This tried and true approach prevents disease.

A new kind of vaccine

Some vaccines contain weakened versions of the bacteria or virus, or just a portion of the organism. These are called antigens, and they kick-start the body’s immune system so it is ready to defend the body if exposed to the disease-causing organism.

But the COVID-19 vaccines developed by Pfizer and Moderna are a new type of vaccine, called an mRNA vaccine (messengerRNA).[2] Instead of exposing the body to a weakened version of COVID-19, mRNA vaccines send cells a tiny genetic message that triggers an immune response.

It’s important to know that the COVID-19 mRNA vaccine cannot give someone COVID-19, and it does not interact with human DNA, because it never enters the nucleus of the cell. And our cells then dispose of the mRNA just like they do with the usual mRNA in our cells.

These vaccines give our cells the ability to make what’s called a ‘spike protein.’ This protein is on the surface of the virus that causes COVID-19. The immune system recognizes the protein as foreign and begins making antibodies, which teaches the body to protect against future COVID-19 infection.

Is the vaccine safe?

All vaccines are rigorously tested and evaluated by the Food and Drug Administration (FDA). This process began in March 2020, and several COVID-19 vaccine candidates were developed and approved for testing, including candidates from Moderna, Pfizer, and others.[3]

Early results from two studies of COVID-19 vaccines show that the vaccines are about 95% effective at preventing people from getting sick with COVID-19. Moderna[4] and Pfizer[5] filed for Emergency Use Authorizations in November 2020 and vaccines were approved for emergency use in December 2020, which  allows them to safely manufacture the vaccine and distribute it to organizations such as UNC Health that are on the frontlines of treating patients.

In addition to the FDA, HHS, the CDC, and the Advisory Committee on Immunization Practices (ACIP), a team of epidemiology and infectious disease experts across UNC Health and the UNC School of Medicine, including Drs. David Weber, David Wohl, Cynthia Gay, and Crystal Cené, have reviewed all available data on the COVID-19 vaccine candidates.

When will it be available?

Everyone who wants a vaccine will eventually get one. However, supplies will be limited. Health experts have recommended vaccinating those most at risk first. Healthcare workers fighting COVID-19 are the first group to get the vaccine. More people will get the vaccines as supply increases throughout 2021 and will be available to anyone.

We are committed to health equity and enabling everyone—no matter what their race, ethnicity, or economic status—to receive the vaccine. This includes both our co-workers and the community we serve, and we pledge equal access within each priority group as set forth by the CDC.


[1] U.S. Food & Drug Administration, Vaccine Development 101, November 20, 2020

[2] CDC, Understanding mRNA COVID-19 Vaccines, November 23, 2020

[3] Fact Sheet: Explaining Operation Warp Speed, November 30, 2020

[4] Moderna, Moderna Announces Primary Efficacy Analysis in Phase 3 COVE Study for Its COVID-19 Vaccine Candidate and Filing Today with U.S. FDA for Emergency Use Authorization, November 30, 2020

[5] Pfizer, Pfizer and Biontech Conclude Phase 3 Study of COVID-19 Vaccine Candidate, Meeting All Primary Efficacy Endpoints November 18, 2020

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