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Coronavirus vaccines: Are they safe?

Vaccines must go through many levels of development before they are given to humans. First, scientists use research to identify or create the best vaccine options. Next, the vaccines are tested in animals, such as mice. If the vaccines show promise in being safe and working to prevent the virus, they are then put through additional phases of safety checks before they become available to the public.

For phase 1 safety trials, the vaccine is tested on a small number of people to confirm it works as intended and is safe. Phase 2 is like Phase 1, but may include hundreds of participants, with a special focus on demographic groups that may respond differently to the vaccine including children and the elderly (whose immune systems may respond differently). Phase 3 trials include thousands of participants and determines how well the vaccine performs compared to a placebo (an inactive treatment). The FDA advocated for a vaccine that protected 50% of those receiving it against SARS-CoV-2, the virus that causes COVID-19. Several recent phase 3 trials have found efficacy at 90% or above. If at any point during these trials there is a concern for the safety of participants, investigators stop the trial to determine what, if any, health problems participants may be experiencing, how they were caused, and whether or not to move forward with the trial.

The New York Times Vaccine Tracker has live updates on the number of vaccine efforts that have passed through each phase, and the number of vaccines approved for limited or widespread use.

Could the vaccine give me COVID-19?

No. You will not develop COVID-19 from getting a vaccine because no trials currently under development in the US use a live virus. 

Does it matter which COVID-19 vaccine I receive?

It is up to you and your physicians. For a vaccine to be approved, the FDA advocated for a vaccine that protected 50% of those receiving it against SARS-CoV-2, the virus that causes COVID-19. As of December 2020, several phase 3 trials have achieved 90% efficacy or above. Although there are some differences in how the vaccines work and how they need to be stored, all candidate vaccines have passed through the same rigorous testing for safety and efficacy. The best approach to reducing COVID-19 in the population is to use whichever safe and effective vaccine is most available. However, the vaccines are not interchangeable; after you receive a first dose of vaccine, you must receive a second dose of the same vaccine.

Once vaccines are available, will other public health measures stop?

The development of safe and effective vaccines against COVID-19 is a valuable medical breakthrough that should help alleviate much of the health and economic burden of the pandemic. However, we do not yet know if the leading vaccine candidates prevent infection (and therefore transmission) in addition to preventing severe disease. Moreover, we do not yet know how long immunity will last. For these reasons,  it is important to continue engaging in the recommended evidence-based public health measures including hand washing, mask use, and social distancing.

How long will it take for a vaccine to be widely available to everyone?

Limited COVID-19 vaccine doses may be available in December 2020, but are likely to be reserved for front-line health care workers. The vaccine supply is expected to greatly increase in 2021 and will become more widely available throughout the year. 

Further credible information about vaccines is shared by the FDA, CDC, NC Department of Health and Human Services (NC DHHS), and Operation Warp Speed. The New York Times Vaccine Tracker has regularly updated information on the status of COVID-19 vaccine trials around the world. See also COVID-19 Vaccine Tracker. For additional information about vaccine development world-wide, see the World Health Organization resource. You can also visit UNC Health's COVID-19 Vaccine Hub.