The US Food and Drug Administration (FDA) has authorised a booster dose of the Pfizer Inc and BioNTech Covid-19 vaccine for those 65 and older, all people at high risk of severe disease, and others who are regularly exposed to the virus, reports Reuters.

The decision paves the way for a quick rollout of the booster shots as soon as this week for millions of people who had their second dose of the vaccine at least six months ago.

The change to the vaccine's emergency use authorisation will allow boosters for groups such as health-care workers, teachers and day care staff, grocery workers and those in homeless shelters or prisons, FDA acting Commissioner Janet Woodcock said in a statement.