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NIH Begins Trial to Test Safety and Effectiveness of COVID Booster Shots

Illustration of two COVID vaccine vials in a bubble surrounded by COVID virus particles.

Leonid studio/Getty

Key Takeaways

  • Researchers at the National Institutes of Health (NIH) are looking at whether they can boost the immune response of people who have been vaccinated against COVID-19 by giving them a booster shot from a different version of the vaccine than they first received. 
  • A clinical trial investigating the safety and efficacy of COVID booster shots will be starting soon that will include 150 adults who have been fully vaccinated with one of the three available COVID vaccines.
  • No booster shot has been developed yet and researchers are not sure when we can expect to have one. However, because coronaviruses typically resurge in the winter months, the clinical trial is starting this summer.

According to the Centers for Disease Control and Prevention (CDC), over 146 million Americans age 12 and older are fully vaccinated against COVID-19. The United States is determined to raise that number while developing potential booster shots that would offer additional protection against the virus.

On June 1, the National Institutes of Health (NIH) announced the launch of a small clinical trial to test the safety and effectiveness of potential booster shots. 

Kirsten Lyke, MD, one of the trial's lead investigators and a researcher at the University of Maryland School of Medicine, tells Verywell that it's one of several trials being run by vaccine manufacturers and research organizations to help us find out if—and when—COVID booster shots might be needed.

Experts continue to stress that the three FDA-authorized COVID-19 vaccines that are currently available in the U.S. are the best way to protect yourself from the virus, as well as the variants that have been identified.

Even though we have safe and effective vaccines, researchers still want to ensure that if and when booster shots are needed, we'll be prepared to deliver them.

Why Do We Need to Test Boosters?

In the news release announcing the new NIH trial, Anthony Fauci, MD, head of the National Institute of Allergy and Infectious Diseases (NIAID) and chief advisor on the coronavirus response to President Biden, emphasized the “strong protection” of the vaccines currently authorized by the U.S. Food and Drug Administration (FDA).

However, Fauci also said that the U.S. needs to “prepare for the possibility of needing booster shots to counter waning immunity and to keep pace with an evolving virus.” 

Kirsten Lyke, MD

We don’t know when a booster might be necessary, but we suspect one will be.

— Kirsten Lyke, MD

Lyke says that the blood tests to be conducted during the trial will help researchers determine whether immunity from the COVID-19 vaccines is beginning to wane, as well as how well we are protected against the known variants.

If new variants emerge during the trial, Lyke says that the boosters will be tested against those as well.

Who Will Be Included?

The first phase of the trial will include 150 adults who have been fully vaccinated with one of the three available COVID vaccines in the U.S.—meaning that they have either received one dose of the Johnson & Johnson vaccine or two doses of the Moderna or Pfizer vaccine.

The news release says, “Each vaccine group will enroll about 25 people ages 18 through 55 years and approximately 25 people age 56 years and older.”

All of the participants will be given one dose of the Moderna COVID vaccine 12 to 20 weeks after they were fully vaccinated.  

Which Shot Will Be Tested?

According to Lyke, the Moderna vaccine was chosen as the booster shot for the trial because the NIH already had contracts in place for its procurement.

Lyke says that the trial will allow researchers to see how recipients of the Pfizer and J&J vaccines respond to a Moderna booster, as well as “what happens when you mix up the platforms.”

Researchers are particularly interested in seeing what happens when the vaccines are “mixed and matched” because they are not the same type of vaccines—the Pfizer and Moderna vaccines use mRNA technology, while the J&J shot is protein-based and uses an adenovirus.

"More versions of vaccines are expected to be authorized in the U.S.," says Lyke. "And the trial will help us find out whether a booster of a different design actually accentuates the immune response above the one you originally received.” 

As the trial progresses, the researchers will look at the possibility of booster shots that are geared toward specific variants of the COVID virus, as well as whether there are combinations of vaccines and boosters that don’t work at all or produce an insufficient immune response.

Lyke says that this information “will help us make decisions,” if and when the shots are needed.

When Will We Get Booster Shots?

Even though the trials will be underway this summer, researchers still don't know when a booster shot will be developed—or even if one will need to be.

“We don’t know when a booster might be necessary, but we suspect one will be,” says Lyke, adding that because winter is when coronaviruses tend to resurge, they "really want to be prepared moving into the autumn to make decisions as to whether we need boosters." 

According to Lyke, the NIH has made the trial “adaptive” which will allow them to quickly switch out vaccines depending on the results—for example, if one does not work or one proves to be superior to the others. 

When asked about the expected timeline, Lyke says, “I don’t know—and anyone who says they do, doesn’t.” 

How Will Boosters Be Distributed?

If researchers determine that COVID boosters are needed—even if they need to be quickly changed out to respond to new threats—Lyke says that the infrastructure for manufacturing the vaccines and distributing them is already in place from the first round that is still in process.

“It just takes a bit of computer code to make the changes to vaccines,” says Lyke. However, she also acknowledges that it will take time to make the billions of booster doses that will be needed around the world—even as first doses still have yet to reach tens of millions of people

Balancing Risk and Benefit

If needing booster shots is even a possibility, why not just give everyone another dose of the vaccine that they already received rather than risk waning immunity and new variants?

Robert Atmar, MD, a lead investigator on the NIH trial and a professor of medicine at Baylor College of Medicine, tells Verywell that cost and safety are the main reasons why this strategy is not being pursued.

“We don’t like to give medicines to people who won’t receive some benefit," says Atmar. "And we don’t know at this point that there would be a benefit."

Atmar also points out that all of the COVID vaccines have produced at least some mild side effects for many. For some people, post-vaccine fevers, headaches, and other symptoms have meant time off work—or at least a day or two down for the count.

Assuming that boosters would come with a similar risk of side effects (and the interruption to one's daily life that may come along with them), Atmar asks, “Why go through that without benefit?”

Angela Shen, ScD, MPH

The more people we get vaccinated, the more the risk goes down.

— Angela Shen, ScD, MPH

While the NIH clinical trial will not be big enough to identify the endpoint—that is, when to give a booster and what to give—Atmar says that “we’ll be able to compare our results with other booster trials underway and we may be able to draw conclusions. We won’t be evaluating our study in a vacuum.”

Angela Shen, ScD, MPH, a visiting research scientist at the Vaccine Education Center at Children’s Hospital of Philadelphia, tells Verywell that she thinks the process underway to evaluate which booster to give and when is a reasonable one because immunity from the vaccine “isn’t a switch that turns on and off, but it rather fades over time.” 

However, Shen says that intensive research isn't all that we need to get ahead of—and ultimately beyond—the COVID pandemic.

“We need more people to get vaccinated, which helps [prevent] variants from taking hold," says Shen. "The more people we get vaccinated, the more the risk goes down.”

What This Means For You

As more people get vaccinated against COVID-19, the question of whether we will need booster shots to continue to be protected from the virus is a major one for researchers. The NIH is already starting a clinical trial that will hopefully allow them to figure out how they would deliver booster shots if and when they are needed.

For now, experts are stressing that the best way to protect yourself and others from COVID is to get one of the three approved vaccines.

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.

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  1. Centers for Disease Control and Prevention (CDC). COVID-19 vaccinations in the United States. Updated June 16, 2021.