People With a Weaker Immune System Should Get COVID-19 Booster, FDA Says

The authorization for a third shot applies to a small fraction of Americans, but more groups could be added later

A healthcare worker placing a Band-Aid on patient's arm after a vaccine has been administered. Photo: iStock

People with a weaker immune system—those who are on immunosuppressant drugs after an organ transplant or who have a condition that impairs the immune system to a similar degree—should get a third dose of the coronavirus vaccine because the standard two-dose regimen might not provide them with adequate protection, the Food and Drug Administration said Thursday.

On Friday, the Centers for Disease Control and Prevention’s Advisory Committee on Immunization Practices, which sets the recommendations for the use of vaccines, endorsed the FDA’s recommendation for a booster shot for moderately or severely immunocompromised people. Additional vaccinations for this group could be available as soon as this weekend.

The authorization for a third dose applies only to people who got the Moderna or Pfizer-BioNTech vaccine, not the Johnson & Johnson single-dose vaccine. The CDC should soon have data to provide guidance to immunocompromised people who received the J&J vaccine, said Amanda Cohn, MD, chief medical officer for the CDC’s National Center for Immunization and Respiratory Diseases, during the ACIP meeting Friday. But very few immunocompromised people have received that vaccine, because it was authorized after the others, she said. Over 90 percent of people who are fully vaccinated in the U.S. received the Moderna or Pfizer-BioNTech vaccine.

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“The country has entered yet another wave of the COVID-19 pandemic, and the FDA is especially cognizant that immunocompromised people are particularly at risk for severe disease,” said Acting FDA Commissioner Janet Woodcock, MD. “After a thorough review of the available data, the FDA determined that this small, vulnerable group may benefit from a third dose of the Pfizer-BioNTech or Moderna vaccines.” The evidence shows that a third vaccine dose can increase protection for these populations, according to the FDA’s announcement.

“An otherwise healthy individual develops a strong immune response after getting fully vaccinated, meaning that they develop antibodies which protect us from getting infected with SARS-CoV-2,” the coronavirus that causes COVID-19, says Ravina Kullar, MPH, PharmD, a fellow of the Infectious Diseases Society of America based in Los Angeles.

But about 3 percent of the population have a condition that weakens the immune system or need to take medications that have a similar effect. Their bodies do not produce as many antibodies to the virus after receiving the vaccine, leaving them vulnerable to infection. In the FDA announcement, the agency said the authorization for a third shot applied to people who had received an organ transplant and those whose immune system was compromised in a similar way.

“This patient population, specifically those with cancer, on chemotherapy, transplant recipients, and on other immunosuppressive agents, inherently have a weaker immune system, and they likely never developed a strong immune response [to the vaccine],” Kullar says. “This population is also at high risk of becoming seriously ill with COVID-19, and they serve as petri dishes to carrying the virus and potentially transmitting it to others. This is even more of a concern with the Delta variant, which is more contagious and transmissible.”

There are a number of studies that show immunocompromised people can benefit from a booster shot, according to Kullar. For example, organ transplant recipients who got a third dose of the Moderna vaccine showed a significant improvement in protective antibody levels compared with those who got a placebo shot, according to a study from a group of researchers in Canada, published in the New England Journal of Medicine.

People who don’t fall into this category do not need a third shot at this time. “Most individuals that are otherwise healthy have a baseline strong immune system and have developed a strong protective immune response after getting fully vaccinated, even with the Delta variant,” Kullar says. 

That said, recommendations for a booster shot for other populations could come in the coming months, especially if data emerges showing that immunity for these groups is declining, either because of time or because of variants of the virus, says Peter Katona, MD, an infectious disease specialist and clinical professor of medicine at the David Geffen School of Medicine at UCLA in Los Angeles. If that happens, he believes that a booster would first be recommended for the elderly and then later for other adults.

“But we don’t know that yet,” Katona says. “We don’t have enough information to say that everybody should get a third shot.”

Editor’s Note: This article was updated with new information from the Aug. 13 ACIP meeting.


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Kevin Loria

I'm a science journalist who writes about health for Consumer Reports. I'm interested in finding the ways that people can transform their health for the better and in calling out the systems, companies, and policies that expose patients to unnecessary harm. As a dad, I spend most of my free time trying to keep up with a toddler, but I also enjoy exploring the outdoors whenever possible. Follow me on Twitter (@kevloria).