How Are Vaccines Tested?

COVID-19 vaccines are a key part of overcoming the pandemic. Fully vaccinated people can start doing some of the things they had to stop. This includes visiting friends and loved ones who are also fully vaccinated.

You might still have questions about vaccines. How do they work? How do scientists know they’re safe? It’s important to know these answers and share them with others. Vaccines are the best protection against many serious diseases. They teach your body to recognize and fight off things like viruses and bacteria. Learn more about what a vaccine is (or watch in Spanish).

The COVID-19 vaccines were developed with amazing speed. But they’re still safe and effective. These vaccines were held to the same standards used to ensure the safety of any approved vaccine. Before a new vaccine is given to people, a lot of testing is done in a lab. Then, it’s tested in people in clinical trials to make sure it’s safe and effective.

There are three phases of clinical trials. Phase 1 is done in a small group of people. Scientists first determine if the vaccine is safe and test different doses. If it passes this phase, it moves on to phase 2. Phase 2 tests the vaccine in more people to see if it works. Researchers look at how the body responds to it and track any side effects. Finally, in phase 3, the vaccine is tested in thousands of people. This rigorous process ensures that any approved vaccine is safe and effective. 

Learn more about how vaccines are tested or watch a video (or watch in Spanish).