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How are COVID-19 vaccines authorized and approved for use?

Last Updated

April 12, 2021

The answers on this site were developed with and vetted by the CDC

Researchers began developing vaccines for COVID-19 in January 2020, based on decades of understanding immune response and how vaccines work. Thousands of volunteers participated in clinical trials that started that spring, making sure we can trust the vaccines to be safe and effective.

Based on the results, the U.S. Food and Drug Administration (FDA) authorized two vaccines for public use in December 2020 and a third in February 2021. The vaccines met the agency’s rigorous and science-based standards for quality, safety, and effectiveness.

COVID-19 is a new virus requiring new vaccines, but vaccines have been saving lives and protecting us for centuries. Now, medical experts believe COVID-19 vaccines can help us move forward in our everyday lives.

What is a clinical trial?

A clinical trial is a research study that helps to make sure a new treatment or vaccine is safe and effective in humans.

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How are vaccines tested for safety?

Every vaccine must go through rigorous testing and inspection to ensure it is safe.

Vaccines for COVID-19 followed a 3-phase process where there are several stages before FDA authorization:

Phase 1: The vaccine is tested in a small number of generally healthy adults, usually between 20 and 80 people. It’s evaluated for safety, dosage, and any side effects. Experts also look at what type of immune response is created.

Phase 2: If there are no safety concerns from Phase I studies, the vaccine is given in various dosages to hundreds of adults who may have a variety of health issues and come from different backgrounds to make sure it is safe. These studies provide additional safety information on common short-term side effects and risks, examine the relationship between the dose given and the immune response, and may provide initial information regarding the effectiveness of the vaccine.

Phase 3: Experts broaden the study to include thousands of adults, from a variety of ages and backgrounds. They see how many people who got the vaccine were protected from the disease, compared to those who received a placebo.

After a vaccine is authorized by the FDA and made available to the public, experts continue to keep track of data to help us learn more about questions like whether vaccinated people can still get infected without having symptoms.

Vaccine testing and approval process (CDC)
How do vaccines get approved or authorized?

Vaccines are approved or authorized by the FDA, which sets strict standards for clinical trials and rigorously evaluates scientific data submitted by vaccine developers.

In December 2020, the FDA authorized two versions of COVID-19 vaccines for the American public. A third was added in February 2021. This means the vaccines may be distributed in the U.S. and given to people above a certain age.

Doctors and medical experts with many years of experience regulating vaccines evaluated information about the safety, effectiveness, and manufacturing quality of the vaccines prior to making their decision. They determined that the known and potential benefits of the vaccines outweigh any known or potential risks.

Two of the authorized vaccines are approved for people 18 and older, and the other is authorized for people 16 and older. Since children under age 16 were not part of the initial tests for these vaccines, none of the vaccines are recommended for children at this time.

How emergency use authorization works (FDA)
Did the clinical trials include people like me?

Researchers made sure that the trials included adults of diverse backgrounds, races, ethnicities, and geographic areas. They collaborated with faith leaders, community organizations, and health clinics to reach volunteers from many different walks of life across the United States.

Medical experts and doctors want to make sure the vaccines work safely and effectively for as many people as possible. People may respond differently to vaccines based on factors like age, gender, and health conditions — so it is important to have a diverse group of participants in clinical trials.

COVID-19 has hit hard in the Black and Hispanic communities. Historically, these populations haven’t always been included in clinical research, but with COVID-19 vaccines researchers made sure volunteers included people of color, as well as people over the age of 65 who are at higher risk of complications from the virus.

About COVID-19 vaccine trials (Duke Health)
How were these vaccines made so quickly?

The science behind the breakthrough had a head start. Researchers had already made progress developing vaccines for other types of coronaviruses: they applied lessons learned after the 2003 SARS epidemic and the 2012 MERS outbreak. They also learned a lot from creating a vaccine for Ebola — which isn’t a coronavirus but has taught us more about viruses.

The rapid spread of COVID-19 made developing these vaccines an international priority, unlocking billions of dollars in funding to ensure safety while moving with urgency to save lives.

Many researchers and medical experts have come together to develop the vaccine while still meeting the FDA’s rigorous requirements for safety and effectiveness. While regulators have streamlined some steps in the vaccine authorization process, the vaccines still needed to meet the agency’s rigorous, scientific standards for safety, effectiveness, and manufacturing quality.

How the FDA evaluated safety data (FDA)