How Vaccine Testing Works

How do we know the vaccine is effective?

Once a vaccine is developed, it must go through rigorous tests to make sure that it works effectively and that it is safe to use. These tests are called clinical trials.

In a clinical trial, people volunteer to take the vaccine. Normally, it is hard to find enough volunteers to get accurate results. But since COVID-19 affected the entire world, there was no shortage of people who wanted to participate. This allowed scientists to run massive trials with tens of thousands of people. Having so many people gives scientists a lot more accurate results.


How a clinical trial works

Half of the volunteers are given the vaccine and half are given a shot without any vaccine in it. They are chosen randomly and even the technicians giving the shot don't know who is receiving the real vaccines and who isn't.

The volunteers are then monitored for side effects after taking the vaccine. They also take tests to see if the vaccine is helping them build up defenses against the virus.

The final test is to measure how many people end up getting sick among the group of volunteers that received the vaccine and the group of volunteers that didn't.

This normally takes a long time to measure with vaccines, but results came back quickly because of how quickly COVID-19 was spreading.


The results

The results were better than expected. Not only did vaccines help prevent you from getting sick in the first place, but more importantly they made it very unlikely that you would go to the hospital or die.

Since the clinical trials, millions more people have received the vaccines, helping scientists to better understand in the real world how effective vaccines are.

A study by the Centers for Disease Control found that vaccines are about 90% effective at preventing hospitalization due to COVID-19.

Getting vaccinated is the best protection to keep you, your family, and your friends safe.