August 11, 2021 -- The FDA could green light a booster dose of the COVID-19 vaccines for people with weakened immune function within the next 2 days.

The agency, along with the CDC and National Institutes of Health, are working through the details of how booster doses for this population would work, according to sources familiar with the agency’s timeline.

About 2.7% of adults in the U.S. are immunocompromised, according to the CDC. This group includes people who have cancer, have received solid organ or stem cell transplants, have genetic conditions that weaken the immune function, have HIV, or people with health conditions that require treatment with medications that turn down immune function, such as rheumatoid arthritis. Immune function also wanes with age, so the FDA could consider boosters for the elderly.

New research shows that between one-third to one-half of immunocompromised patients who didn’t develop detectable levels of virus-fighting antibodies after two doses of a COVID vaccine, will respond to a third dose.

A committee of independent experts that advises the CDC on the use of vaccines in the U.S. had previously signaled its support for giving boosters to those who are immunocompromised, but noted that it couldn’t officially recommend the strategy until the FDA had updated its emergency use authorization for the shots or granted them a full biologics license, or “full approval.”

It’s unclear which mechanism the FDA might use, or exactly who will be eligible for the shots.

The U.S. would follow Israel, France, the UK, and Germany in authorizing boosters for some vulnerable individuals.

The World Health Organization has voiced strong opposition to the use of boosters in wealthy countries while much of the world still doesn’t have access to these lifesaving therapies. The WHO has asked wealthy nations to hold off on giving boosters until at least the end of September to give more people the opportunity to get a first dose.

The CDC’s Advisory Committee on Immunization Practices (ACIP) meets again on Friday and is expected to discuss booster doses for this population of patients. The ACIP officially makes recommendations on the use of vaccines to the nations doctors. Their recommendation ensures a vaccine will be covered by public and private insurers. Statutory vaccination requirements are also made based on the ACIP’s recommendations.