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November 18, 2021

How do we know COVID-19 vaccines are safe?

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

More than 170 million people in the United States, including 96% of medical doctors, are now fully vaccinated against COVID-19. These vaccines have been through the most intensive safety monitoring in U.S. history.

Vaccines are approved and authorized by the U.S. Food and Drug Administration (FDA), including full approval for the Pfizer vaccine (Comirnaty) which was granted in August 2021. The FDA sets strict standards for clinical trials and carefully reviews scientific data from vaccine developers. Once vaccines are made available to the public, the FDA continues to monitor them very closely.

Researchers began developing vaccines for COVID-19 in January 2020, based on decades of work on immune responses and vaccine technology. Thousands of volunteers took part in the clinical trials that started that spring to ensure the vaccines are safe and effective.

Based on the results, the FDA authorized multiple vaccines for public use. In December 2020, the FDA authorized the Moderna and Pfizer-BioNTech vaccines for the American public. Johnson & Johnson’s Janssen vaccine was added in February 2021 and is currently available for use in the United States after a pause in April 2021. In August 2021, the Pfizer vaccine (Comirnaty) became the first vaccine to be fully approved by the FDA based on extensive data on safety and effectiveness.

Doctors and medical experts with many years of experience regulating vaccines looked at information about the safety, effectiveness, and quality of the vaccines before making their decision.

After a vaccine is approved or authorized by the FDA and made available to the public, experts continue to closely monitor it for safety and to help us learn more about questions like how long vaccines provide protection.

Ted Obi -- What’s A Clinical Trial | COVID-19 Vaccine Education Initiative | Ad Council
Safety of COVID-19 Vaccines (CDC)

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Are the COVID-19 vaccines fully approved by the FDA?

In August 2021, FDA announced full approval of the Pfizer-BioNTech vaccine for ages 16 and up. The Pfizer vaccine is also available to children aged 5 to 15 under emergency use authorization.

The Moderna & J&J vaccines are still available under emergency use authorization as the FDA continues to review all available data. All three COVID-19 vaccines are extremely effective at preventing serious illness, hospitalization, and death – even from the Delta variant.

Comirnaty and Pfizer-BioNTech COVID-19 Vaccine Frequently Asked Questions (FDA)
What’s the difference between full FDA Approval and Emergency Use Authorization?

Full approval represents the FDA’s highest level of confidence in a drug’s safety and effectiveness.

Full FDA approval takes longer than Emergency Use Authorization (EUA). More data needs to be processed and reviewed over a longer period of time. When the FDA fully approves a product, patients can be sure the approval is based on large amounts of scientific data.

In some emergencies, the FDA issues an EUA to give access to critical medical products because no approved products are available. This has been the case with the COVID-19 public health emergency, which is why vaccines were first available under an EUA.

What is an EUA?
How were the 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. It unlocked 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 authorization process, the vaccines still needed to meet the FDA’s high standards for safety, effectiveness, and manufacturing quality.

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

How the FDA evaluated safety data (FDA)
How are vaccines tested for safety?

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

COVID-19 vaccines followed a 3-phase process. Several important stages were required before FDA authorization and approval.

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 come from different backgrounds and may have varied health issues. These studies provide more safety information on common short-term side effects and risks. They look at the relationship between the dose given and the immune response, and may provide initial insight into how effective the vaccine is.

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, FDA continues to monitor its safety very closely. FDA also continues to oversee the production of the vaccine, including periodic safety checks on facilities where it is made.

Vaccine testing and approval process (CDC)
Did the clinical trials include people like me?

Researchers made sure that the trials included adults from many types of backgrounds, races, ethnicities, and geographies. They worked closely with faith leaders, community groups, and health clinics across the United States to reach volunteers from different walks of life.

Medical experts 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. 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)
Dr. Bright – Clinical Trials
How did the COVID-19 vaccines get authorized and approved?

Vaccines are authorized and approved by the U.S. Food and Drug Administration (FDA). It sets strict standards for clinical trials and carefully reviews scientific data from vaccine developers.

In December 2020, the FDA authorized the Moderna and Pfizer-BioNTech vaccines for the American public. Johnson & Johnson’s Janssen vaccine was added in February 2021. The FDA granted full approval to the Pfizer vaccine in August 2021 based on an extensive review of data on safety and effectiveness.

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

After a vaccine is authorized by the FDA and made available to the public, experts continue to closely monitor it for safety and to help us learn more about questions like whether vaccinated people can still get infected without having symptoms.

How emergency use authorization works (FDA)
Do vaccines impact fertility?

After extensive clinical trials and close examination, there is no evidence that any vaccines, including COVID-19 vaccines, cause fertility problems. In August 2021, FDA granted full approval to the Pfizer vaccine (Comirnaty) and confirmed there is no scientific evidence to suggest that the vaccine could cause infertility.

If you are trying to become pregnant now or want to get pregnant in the future, you may safely receive a COVID-19 vaccine.

COVID-19 Vaccines While Pregnant or Breastfeeding (CDC)
Dr Susan Huang MD

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