New York, Nov 20 (IANS): The US Food and Drug Administration (FDA) has authorized boosters of the Pfizer or BioNTech and Moderna Covid-19 vaccines for all adults.

The agency expanded emergency use authorization for booster doses of both the mRNA vaccines beyond who was previously eligible -- boosters had been authorized for anyone 65 years and older who was vaccinated with the Pfizer or Moderna vaccines at least six months ago and for certain adults at high risk of infection or of severe disease.

Pfizer and BioNTech requested authorization last week based on results of a Phase-3 trial involving more than 10,000 participants. It found boosters were safe and had an efficacy of 95 per cent against symptomatic Covid-19 compared with the two-dose vaccine schedule in the period when the highly transmissible Delta was the dominant strain, Xinhua news agency reported.

Moderna requested authorization of its 50 microgram booster dose for all adults on Wednesday. The company said the FDA based the emergency use authorization (EUA) on the "totality of scientific evidence shared by the company," including data that showed neutralizing antibodies had waned at about six months.

The outside vaccine experts of the US Centers for Disease Control and Prevention (CDC) are scheduled to meet on Friday to discuss the FDA's actions on the application from Pfizer-BioNTech and Moderna.

The advisers will recommend how the boosters should be used. If CDC Director Rochelle Walensky signs off on broader use, the extra shots could be available for all adults as soon as this weekend.

"The vaccine makers' requests for broad authorization come as a growing number of states are offering boosters to all adults, going beyond the current guidance from the CDC that recommends limiting eligibility to specific groups. Efforts to accelerate the booster campaign are designed to bolster waning immunity from the initial vaccinations and reduce breakthrough infections and viral transmission," reported The Washington Post on Friday.