The U.S. Is Testing 3 Possible COVID-19 Vaccines

Dr. Anthony Fauci announced the U.S. will provide funding to test three possible COVID-19 vaccines


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Key Takeaways

  • The U.S. is funding clinical trials for COVID-19 vaccines from Moderna, AstraZeneca, and Johnson & Johnson
  • Moderna and AstraZeneca have already begun human trials
  • The most optimistic projections say the first doses of a vaccine could be available this fall

Earlier this month, Anthony Fauci, MD, director of the National Institute of Allergy and Infectious Diseases (NIAID), announced U.S. government plans to fund research for three candidates for a COVID-19 vaccine.

Fauci's statement was originally reported by The Wall Street Journal on June 10, with additional coverage from CNN and other major news outlets as the details of the plan emerged.

The announcement came just as the U.S. hit a new milestone in COVID-19 cases: over 2 million people in the U.S. have been diagnosed with the virus as of the first week of June.

COVID-19 Vaccine Candidates

According to data from the World Health Organization (WHO), there are over 140 potential COVID-19 vaccines currently in development around the world, and that number is likely to increase.

While more candidates will be added, the three possible candidates the U.S. has pledged to help fund through manufacturing include:

  • Moderna
  • AstraZeneca
  • Johnson & Johnson

What This Means For You

According to Fauci, by fast-tracking funding and approval for clinical trials, the U.S. will be on track to have a COVID-19 vaccine "at scale" by early next year. He hopes that at least one of the vaccine candidates will be successful enough to supply 100 million doses by 2021.


Moderna is an American biotech company founded in 2010. The company is headquartered in Massachusetts and is primarily focused on drug discovery and development.

Most of the work Moderna does involves a special kind of genetic molecule called messenger RNA (mRNA). These tiny messengers tell DNA what to do. Moderna's labs are working to make mRNA that can be put into vaccines and other types of medical treatment.

Where Is the Vaccine In Development?

Participants in the Phase 2 trial received their first dose of the vaccine on May 29 and their second (and final) dose on June 11.

Phase 2 involved 600 healthy participants split into two age cohorts: adults age 18 to 55 and adults age 55 and older. Participants were either administered a placebo, a 50 microgram (μg) dose of the vaccine, or a 100 μg dose of the vaccine.

During Phase 3, Moderna plans to enroll 30,000 participants for a randomized, placebo-controlled trial. According to the company's press release, NIAID—which is part of the National Institutes of Health (NIH)—will collaborate on the trial.

Phase 3 is expected to start in July.

A vaccine can earn FDA approval after passing successfully through Phase 3 clinical trials.

How Will the Vaccine Work?

Moderna's vaccine candidate, mRNA-1273, targets a specific protein in the virus that causes COVID-19 (SARS-CoV-2). Other biotech companies have tried working with mRNA in the past but have not been successful. The science of using mRNA for medical applications is still very new and most of the research has pertained to cancer treatment.

By making their own mRNA, scientists can give molecules specific directions (called encoding), which they will then pass on to the body's DNA. In the case of a COVID-19 vaccine, the synthetic mRNA is programmed to cause cells in the body to create the spikes found on the surface of SARS-CoV-2 viral proteins. Scientists hope that the spikes, which are harmless on their own, will elicit the immune response necessary to create antibodies against SARS-CoV-2.

The spikes give the cells a crown-like appearance under a microscope. That's how coronaviruses got their name; "corona" is Latin for "crown."


AstraZeneca is a biopharmaceutical company founded in 1992. It's headquartered in the United Kingdom, but also has arms in the U.S. and Sweden. The company is working with researchers from Oxford University in England to develop a COVID-19 vaccine.

Where Is the Vaccine In Development?

AstraZeneca's vaccine candidate, AZD1222, is currently being tested in 10,000 volunteers in the U.K. The Phase 2/3 trials began in May and are still underway. This phase of the trial will be expanded to include people in different age ranges, including children and the elderly.

The next intended step is a Phase 3 trial this summer, which will require 25,000 to 30,000 volunteers.

If the trials stay on the accelerated track, AstraZeneca hopes to start sending doses of its vaccine to the U.K. in September and the U.S. in October.

How Will the Vaccine Work?

AZD1222 (ChAdOx1 nCoV-19) is a recombinant adenovirus vaccine. A weakened version of the virus that usually gives people the common cold (adenovirus) is used to transport genetic proteins from specific SARS-CoV-2 proteins into the body, where it triggers an immune response.

The modified viruses in the vaccine are strong enough to make the body respond and build up immunity, but are not able to replicate and make someone sick.

Johnson & Johnson

Johnson & Johnson is one of the largest manufacturers in America. The company makes a range of medical devices, pharmaceuticals, and consumer goods. It was founded in 1886 and is headquartered in New Jersey.

Where Is the Vaccine In Development?

Johnson & Johnson announced its COVID-19 vaccine candidate, Ad26.COV2-S, in March of 2020. On June 10, the company announced that its Phase 1/2a first-in-human clinical trial originally scheduled for September had been moved up to the second half of July.

The vaccine trial—a randomized, double-blind, placebo-controlled Phase 1/2a study—will take place in the U.S. and Belgium (the location of one of its subsidiaries, Janssen Pharmaceutical Companies) and involve 1,045 volunteers.

Once the results of this phase have been reviewed, Johnson & Johnson will be able to move to Phase 3.

How Will the Vaccine Work?

Johnson & Johnson's vaccine is being developed similarly to its Ebola vaccine in 2019: by combining viruses. The COVID-19 vaccine contains genetic material from SARS-CoV-2 as well as an adenovirus.

By using something called AdVac technology, Johnson & Johnson is creating a vaccine by removing a piece of an adenovirus's genetic sequence and plugging in the genetic code from COVID-19. During this process, the virus's ability to reproduce itself is eliminated.

Why Trial More Than One Vaccine?

When there is an urgent need for a vaccine, it's wise to have more than one iron in the fire. One vaccine candidate might show promise early on, but if later testing shows it poses more risk to people than benefit, it would likely not be approved for use.

Having multiple vaccine candidates go through the testing and approval process makes it more likely that at least one will emerge as a safe and effective option for the public.

In the best-case scenario, several vaccine options will emerge. In that case, regulatory organizations would have the ability to choose the one that offers the most benefit, poses the least risk, and costs the least to produce and distribute.

How Clinical Trials Work

Before any potential vaccine can be given to large numbers of people, it needs to be rigorously tested to ensure that it works and that it is safe.

Vaccine research, development, and distribution is usually a years-long process, but in times of crisis, regulatory agencies like the Food and Drug Administration (FDA) may agree to speed up the process. That said, making the process go faster doesn't mean steps are skipped. There are still phases of testing that a vaccine needs to go through—and pass—before production can be scaled up and the vaccine given to people.

What Happens During Each Phase of a Clinical Trial?

Each phase of a clinical trial builds on the results of the previous one. Researchers usually want to start small and work their way up to testing a device or drug in large numbers of people. The first tests might be in a test tube or petri dish, followed by trials in animal subjects. Then, it might be approved for testing in humans.

For a new vaccine, researchers will look at the results of each phase to see how well it works and what (if any) side effects occur. They will also continue to weigh any risks associated with the vaccine against the potential benefit.

Phase 1

Researchers start by testing the vaccine in a small number of healthy people. During Phase 1 of a clinical trial, they will try to determine what dose is effective and will monitor its safety. This phase usually takes several months.

Phase 2

If Phase 1 trials go well, researchers will scale up and test more people during Phase 2—including people who might be in high-risk categories, like the elderly and children. Phase 2 can take anywhere from a few months to a couple of years.

Phase 3

There are usually several hundred to several thousand volunteers in a Phase 3 trial. During this phase, researchers are looking to see how well the treatment works and what adverse effects or outcomes it has.

They usually compare their treatment to treatments that already exist to see which one works better and/or has fewer side effects or adverse outcomes.

Phase 3 clinical trials usually take 1 to 4 years to complete, but on the "fast-track" may only last a few months.

Phase 4

Phases 4 can happen after FDA approval. It is designed to test the vaccine in much larger numbers of people (several thousand) over a longer period of time (usually several years). This final phase tells researchers if a treatment works long term and whether it has any side effects or adverse outcomes.

At each phase of a clinical study, participants usually have to meet rigorous standards to be involved. Researchers want to minimize risk to people who agree to be part of the study but also want to get a fairly good representation of the overall population intended to receive the vaccine.

A Word From Verywell's Medical Expert Board

"Developing a new vaccine typically takes many years. Products need to be put through several phases of testing before they can be marketed. This is to make sure they are both safe and effective. Scientists have been working around the clock for months on a coronavirus vaccine. Three vaccines are now ready to be tested in large human trials this summer. If all goes well, we may have one (or even three!) vaccines by early 2021." – Anju Goel, MD, MPH

The information in this article is current as of the date listed, which means newer information may be available when you read this. For the most recent updates on COVID-19, visit our coronavirus news page.

14 Sources
Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
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By Abby Norman
Abby Norman is a freelance science writer and medical editor. She is also the author of "Ask Me About My Uterus: A Quest to Make Doctors Believe in Women's Pain."