Plans to give millions of Americans booster shots for Covid-19 have been approved by the US Centres for Disease Control and Prevention.

The move starts a major new phase in the country’s vaccination drive against the pandemic.

Advisers said boosters should be offered to people 65 and older, nursing home residents and those ages 50 to 64 who have underlying health problems.

The extra dose would be given at least six months after a patient’s last Pfizer shot, and the plans were signed off by director Dr Rochelle Walensky late on Thursday.

However, Dr Walensky decided to make one recommendation that the panel had rejected.

The panel on Thursday voted against saying that people can get a booster if they are ages 18 to 64 years and are healthcare workers or have another job that puts them at increased risk of being exposed to the virus.

But Dr Walensky disagreed and put that recommendation back in, noting that such a move aligns with a Food and Drug Administration booster authorisation decision earlier this week.

The panel had offered the option of a booster for those ages 18 to 49 who have chronic health problems and want one.

But the advisers refused to go further and open boosters to otherwise healthy frontline health care workers who are not at risk of severe illness but want to avoid even a mild infection.

The booster plan marks an important shift in the nation’s vaccination drive.

The United Kingdom and Israel are already giving a third round of shots over strong objections from the World Health Organisation that poor countries do not have enough for their initial doses.