• The FDA has expanded the emergency authorizations for leading COVID-19 vaccines. 
• That paves the way for patients with weakened immune systems to start receiving booster shots.
• It remains unclear when, or if, extra doses would be rolled out to everyone in the US.

The US Food and Drug Administration on Thursday took a key step toward allowing some of the most vulnerable Americans to receive booster shots — or a third dose — of coronavirus vaccines.

The FDA tweaked the language in its emergency authorizations for the Pfizer-BioNTech and Moderna COVID-19 vaccines to allow doctors to consider giving additional doses for people with weakened immune systems. Previously the Pfizer-BioNTech and Moderna shots were intended to be given as two doses several weeks apart, while J&J’s shot was given as a single dose.

In recent weeks, US health officials and doctors have highlighted the need to start offering booster shots to certain groups of people with weakened immune systems, such as people who have received organ transplants. Giving an additional vaccine dose could help boost those people’s protection against COVID-19.

Other countries, including Germany, France, and the UK, have already firmed up plans to soon start rolling out booster shots to their most vulnerable populations. Israel started offering extra shots to people with impaired immune systems in July.

CDC expected to urge immunocompromised to talk to their doctors about a booster dose

Offering shots to some people with weakened immune systems is likely the first step in a broader booster-shot campaign.

About 2.7% of adults in the US, or 7 million people, have severely weakened immune systems, according to the Centers for Disease Control and Prevention. It’s not clear whether the CDC will recommend that all immunocompromised people receive booster shots.

Diseases like HIV can weaken the immune system, as can certain cancer treatments and some drugs given to people who have received organ transplants or to treat conditions like arthritis.

Several research studies have shown that immunocompromised people mount far less of a response to the COVID-19 vaccines than the population at large. Some small studies suggest an extra dose boosted antibodies in about one-third to half of immunocompromised patients.

Dr. Camille Kotton, an infectious-disease and transplant specialist at the Massachusetts General Hospital, said at a CDC meeting in July that many patients “have taken matters into their own hands and are proceeding with additional doses as they see fit.”

Kotton sits on an independent advisory committee to the CDC, which issues recommendations on how to use vaccines.

That committee has discussed the topic of booster shots for immunocompromised people, but its members have said they needed to wait for the FDA to update the authorizations for the vaccines before recommending any booster shots.

Kotton said the regulatory situation limited doctors from recommending booster shots. 

That CDC advisory group is set to meet on Friday to further discuss booster doses. While a formal vote is not on the agenda, the advisory group is expected to urge immunocompromised people to talk with their doctors or pharmacists about getting an additional shot, The Washington Post reported. 

FDA’s actions do not mean booster shots for everyone

While the vaccine makers Pfizer and Moderna have argued that everyone should get a third shot of their vaccines after six to 12 months, US regulators and public-health officials are, so far, unconvinced. 

The drug companies have cited data showing modest declines in real-world protection against the virus, particularly with the rise of the Delta variant. They’ve coupled that with lab studies showing large drops in virus-fighting antibody levels, which they say support the case that protection wanes after at least six months. 

“We believe a booster dose is likely to be necessary this fall,” Moderna President Stephen Hoge said on August 5.

Vaccine experts like Dr. Paul Offit, who sits on the FDA’s vaccine-advisory committee, have said that booster doses wouldn’t be needed unless fully vaccinated people started to get seriously ill from COVID-19.

The FDA is working on a more comprehensive plan for boosters, and The Wall Street Journal reported that work won’t be completed until early September.