The US Food and Drug Administration authorized a third dose of COVID-19 vaccines from Pfizer and Moderna for people with compromised immune systems.

The amended emergency use authorization paves the way for people who have had an organ transplant, or those with a similar level of weakened immune system, to get an extra dose.

“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,” Janet Woodcock, US FDA’s acting commissioner, said in a tweet on Thursday.

“Others who are fully vaccinated are adequately protected & do not need an additional dose of COVID-19 vaccine at this time.”

The vulnerable group of patients make up less than 3% of US adults, Rochelle Walensky, director of the Centers for Disease Control and Prevention (CDC), had said before the authorization.

A panel of advisers to the CDC will meet on Friday to discuss booster doses, and a vote later by the committee will help decide on the roll out of the extra shots.

Scientists are still divided over the broad use of COVID-19 vaccine boosters among those without underlying problems as benefits of the boosters remain undetermined.

Pfizer has said the efficacy of the vaccine it developed with BioNTech drops over time, citing a study that showed 84% effectiveness from a peak of 96% four months after a second dose.

Moderna has also said it sees the eventual need for booster doses, especially since the Delta variant has caused “breakthrough” infections in fully vaccinated people.

Reports of infections among vaccinated people and concerns about diminishing protection have galvanized wealthy nations to distribute booster shots, even as many countries struggle to access first vaccine doses.

The World Health Organization last week called for a moratorium on COVID-19 vaccine booster shots until at least the end of September.

Wall Street analysts expect the authorization of a booster dose for a broad population to bolster profits of COVID-19 vaccine makers. – Rappler.com