USA – The U.S. Food and Drug Administration on Thursday authorized a booster dose of COVID-19 vaccines from Pfizer Inc and Moderna Inc for people with compromised immune systems.

A few other countries, such as Israel and Germany, plan to or have already administered the third shot to avoid another crisis due to the contagious Delta variant of the coronavirus.

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.

The company said it could apply for an emergency use authorization (EUA) for a booster dose as early as this month.

Data showed that a third dose generated virus-neutralizing antibodies more than 5 times higher in younger people and more than 11 times higher in older people than from two doses against the more easily transmissible Delta variant of the virus.

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.

The U.S. health regulator amended the emergency use authorizations for the vaccines to allow an additional dose in certain individuals, specifically for recipients of solid organ transplant or those diagnosed with conditions that are considered to have an equivalent level of immunocompromise.

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.

However, those with weak immune systems may not be sufficiently protected by their existing COVID-19 vaccinations, U.S. health officials have said.

It is extremely important for us to move to get those individuals their boosters and we are now working on that,” U.S. infectious disease expert Dr. Anthony Fauci had said.

Wall Street analysts expect the authorization of a booster dose for a broad population to bolster profits of COVID-19 vaccine makers, as hundreds of millions of fully inoculated people will come back for an extra dose.

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