WASHINGTON: The US Food and Drug Administration on Monday fully approved Pfizer's Covid-19 vaccine, a move expected to trigger a new wave of vaccine mandates as the Delta variant batters the country.

"The FDA's approval of this vaccine is a milestone as we continue to battle the Covid-19 pandemic," acting FDA Commissioner Janet Woodcock said in a statement.

"While millions of people have already safely received Covid-19 vaccines, we recognize that for some, the FDA approval of a vaccine may now instill additional confidence to get vaccinated."

The Covid vaccine, which may now be marketed under its brand name Comirnaty, is the first to receive full approval.

Tens of millions of shots have already been administered under an emergency use authorization (EUA) that was granted on December 11, 2020.

Third Pfizer dose 86% effective in over 60s, Israeli HMO says

The decision to award it approval was based on updated data from the drug's clinical trial, including a longer duration of follow-up, with safety and effectiveness evaluated among more than 40,000 people.

The US military has previously announced it will mandate the vaccine as soon as it receives full approval, and a slew of private businesses and universities are expected to follow.

The vaccine remains available under emergency use authorization to children aged 12 to 15, but because it has now been fully approved, physicians may prescribe it to children under 12 if they believe it will be beneficial.