British officials on Tuesday recommended Covid-19 vaccine booster shots be given to all vulnerable people and those aged over 50, ahead of an announcement by the government on its strategy for taming infections this winter.
The Joint Committee on Vaccination and Immunisation's recommendation of a third dose, to be given six months after a second shot, paves the way for a broad revaccination programme in Britain.
"The main aim of the booster programme is to prolong that protection and reduce serious disease as we head towards the colder months," said the JCVI's Professor Wei Shen Lim.
The advice comes ahead of a media conference later on Tuesday when Prime Minister Boris Johnson will detail the government's winter strategy with a warning that the battle against the virus was not over.
The government has already indicated it would scrap plans for vaccine passports to be required to get into nightclubs, end some of its emergency Covid powers and use lockdowns only as a last resort.
Instead, Johnson will lean on vaccines and testing to try and contain Covid-19 heading into autumn and winter.
"The pandemic is far from over, but thanks to our phenomenal vaccine programme, new treatments and testing we are able to live with the virus without significant restrictions on our freedoms," Johnson said in a statement.
"Today I will set out a clear plan for the autumn and winter, when the virus has a natural advantage, to protect the gains we have made."
Britain has recorded 134,000 Covid-19 deaths, and more than 7 million cases. So far 44 million people have had two vaccine doses, 81 percent of those aged over 16. On Monday, the government said those aged 12 to 15 would also be offered shots.
Johnson scrapped the last coronavirus restrictions in England in July, citing the more favourable conditions of the school summer holidays as he eyed what he characterised as a "return to normal".
The JCVI had already given interim advice that elderly and vulnerable people would be the priority for any booster programme, and that it could start in September.
It said its preference was that the Pfizer vaccine was used for the booster dose, or alternatively a half-dose of a Moderna shot. Britain ordered 60 million additional Pfizer doses for the booster programme in April.
Meanwhile, some leading scientists, including from the U.S. Food and Drug Administration and World Health Organisation, in an article in the Lancet medical journal on Monday said Covid-19 boosters are not yet needed for the general population.