The US has authorised the use of boosters of Pfizer's Covid-19 vaccine for people aged over 65, as well as adults at high risk of severe disease.
The announcement means tens of millions of Americans are now eligible for a third shot six months after their second dose. "Today's action demonstrates that science and the currently available data continue to guide the FDA's decision-making for COVID-19 vaccines during this pandemic," said Janet Woodcock, acting head of the Food and Drug Administration (FDA).
The decision was expected and came after an independent expert panel convened by the regulatory agency last week voted in favour of recommending the move.