The U.S. Food and Drug Administration (FDA) has approved three COVID-19 vaccines for emergency use in the United States. Health officials at the federal, state, and local level are now working to deliver millions of doses and vaccinate people across the country.

You may have questions about the vaccines — how they were developed, if they’re safe, and when you’re eligible to get one.

COVID-19 Vaccines Timeline

It usually takes 10 to 15 years to develop a vaccine and make it available to the public. Scientists developed the COVID-19 vaccines more quickly because of previous research into the virus that causes the disease, called SARS-Cov2. SARS-Cov2 is only one coronavirus. Others can cause diseases like the common cold.

Long before the start of the COVID-19 pandemic, experts were investigating coronaviruses to find out how to keep people from getting sick. Scientists created a vaccine for one “prototype” coronavirus, which they could then modify to combat different coronaviruses. This approach, along with other research around the world, gave them a head start in developing the COVID-19  vaccines.

Here’s a look at the timeline from the first reported outbreak of COVID-19 to approval of the first vaccines:

December 2019: Officials report the COVID-19 outbreak in China to the public.

January 2020: Researchers in China publish the DNA sequence of the coronavirus that causes COVID-19 (SARS-CoV-2)

March-April 2020: COVID-19 vaccines from Moderna,  Pfizer-BioNTech, and AstraZeneca go into the first phase of clinical trials. This phase is where scientists test the vaccine on a small group of adults to assess its safety and volunteers’ immune response.

May 2020: Moderna begins phase 2 of its clinical trials. During this phase, scientists figure out vaccine dosage and continue to evaluate its safety.

July 2020: Janssen’s (Johnson & Johnson) vaccine enters phases 1 and 2 of clinical trials. The company combined these phases to shorten the vaccine development timeline. Meanwhile, Moderna begins phase 3 of its COVID-19 vaccine clinical trial. And, Pfizer starts its combined phases 2 and 3.

August 2020: AstraZeneca starts its combined phases 2 and 3 of clinical trials.

September 2020: Janssen begins phase 3 clinical trials. More volunteers continue to receive the vaccine to find out if it’s effective.

December 2020: The FDA approves the Pfizer-BioNTech and Moderna vaccines for emergency use in the United States. The same month, the United Kingdom approves the AstraZeneca vaccine for use there.

February 2021: Janssen’s COVID-19 vaccine is approved by the FDA for emergency use in the United States.

March 2021: Several European countries temporarily halt the AstraZeneca vaccine rollout after reports of blood clot-related complications. The European Medicines Agency conducted an investigation and found that the vaccine is safe, works well, and that its benefits outweigh any potential risks. While some countries have resumed vaccinations, others have extended the suspension.

Also in March, the National Institute of Allergy and Infectious Diseases (NIAID) released a letter stating that AstraZeneca published outdated data, which provided an incomplete picture of its vaccine’s effectiveness. The company released results with up-to-date data showing the vaccine is 69 to 74% effective versus 79% that they’d initially reported. To date, the FDA has not approved the AstraZeneca COVID-19 vaccine for use in the U.S.

Frequently Asked Questions

You may have some questions about the COVID-19 vaccines — how they work and could affect you.

Do the COVID-19 vaccines contain the virus that causes COVID-19?

No. None of the vaccines that the FDA has approved for use in the United States, or ones in development, have the live virus that can make you sick with COVID-19. 

I’ve already had COVID-19. Why do I need to get vaccinated?

If you’ve had COVID-19, you may have some level of natural protection, or immunity, from getting sick again. But, experts aren’t sure how long this protection lasts. Even though it’s rare, there’s a chance that you could get re-infected after recovering from COVID-19.

It’s also important to keep in mind that the risk of severe illness, death, and spreading the virus to others outweigh the benefits of natural immunity. With a COVID-19 vaccine, you’re protected without getting sick from the virus.

Does a COVID-19 vaccine shield me from illness from the COVID-19 virus?

Yes. A COVID-19 vaccine protects you from getting sick by showing your immune system how to spot and fight the virus that causes COVID-19. Many people only get mildly sick from COVID-19. But, there’s no way to know for sure if you’ll get seriously ill, have long-term health problems, or die from the disease.

Will a COVID-19 vaccine change my DNA?

No. Your DNA is located in the nucleus of your cells, and a COVID-19 vaccine never goes into this part of your cells.

Both the Pfizer-BioNTech and Moderna COVID-19 vaccines are messenger RNA (mRNA) vaccines, which teach your cells how to make a protein that sets off an immune response in your body. The Janssen COVID-19 vaccine is a viral vector vaccine. This type of vaccine uses a safe virus (vector) that serves as a platform to make coronavirus proteins to create an immune response.

What is an emergency use authorization (EUA) for vaccines?

During public health emergencies like the COVID-19 pandemic, the FDA makes unapproved medical products available more quickly than what is typical. The FDA evaluates each EUA request, and still requires safety and effectiveness data from manufacturers.

Caregivers and the COVID-19 Vaccines

If you’ve decided to get one of the approved COVID-19 vaccines, you may be eligible as a caregiver. While most states aren’t including caregivers in early vaccine phases, some are.

  • Oregon and Massachusetts are allowing paid and unpaid caregivers to be vaccinated if they meet specific criteria.
  • In California, family members of people with conditions like Down syndrome, epilepsy, and cerebral palsy can get a COVID-19 vaccine, while in Illinois, you must be a caregiver.
  • South Carolina says caregivers of children with certain medical conditions can get the shots.
  • In Michigan, caregivers of people who receive Medicaid and those who care for children with special health care needs are eligible for the vaccines.

As states receive more vaccine supplies, they will continue to open up eligibility to more groups. Check with your state health department to find out when you can get vaccinated.

This article was created by our partner, Clara Health. Clara Health was founded to democratize access to clinical trials and ease the administrative burden often placed on patients and caregivers to find and enroll in studies. You can visit them at

Last updated March 2021.