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Are COVID-19 vaccines safe and effective? How were they tested and approved?

Last Updated: 12/29/2020

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 known and potential benefits of approved vaccines outweigh the known and potential harms of becoming infected with COVID-19.

The U.S. Food and Drug Administration (FDA) has granted Emergency Use Authorizations (EUAs) for two COVID-19 vaccines which have been shown to be safe and effective as determined by data from the manufacturers and findings from clinical trials.

More information from the FDA about these two vaccines can be found here:

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

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

Clinical Trials
Several vaccines are in Phase 3 clinical trials and the FDA has issued EUAs for the Pfizer-BioNTech vaccine and for the Moderna vaccine. For more details on the vaccine approval process, refer to this infographic and this fact sheet.

Clinical trials are research studies performed in people that are aimed at evaluating a medical, surgical, or behavioral intervention. They are the primary way that researchers find out if a new treatment, like a new drug, vaccine, or medical device is safe and effective in people.

Currently, clinical trials are evaluating COVID-19 vaccines in many thousands of study participants to generate scientific data and other information for the FDA to determine their safety and efficacy. These clinical trials are being conducted according to rigorous safety standards. For detailed information, visit this CDC page.

Side Effects
After receiving an injection of a COVID-19 vaccine, you will be observed for 15 minutes by healthcare staff to monitor any side effects. Observation may be longer (30 minutes) if you have a history of anaphylaxis.

Like many vaccines, a COVID-19 vaccine may cause some temporary discomfort. In addition to a sore arm, side effects of the vaccines may include tiredness, headache, muscle pain, chills, joint pain, fever, injection site swelling, injection site redness, nausea, feeling unwell, and swollen lymph nodes.

There is a small chance that vaccines could cause a severe allergic reaction. A severe allergic reaction would usually occur within a few minutes to one hour, which is why all individuals should be observed for at least 15 minutes after vaccination and 30 minutes if they have a history of a severe allergic reaction due to any cause.
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.

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