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

“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.”