Covid-19 booster jabs have been extended to the over-40s, the Joint Committee on Vaccination and Immunisation (JCVI) has announced.
The change means the booster programme will be extended to include people aged between 40 to 49, who are eligible for a third jab six months after receiving their second dose.
The JCVI said people should be offered the Pfizer or Moderna jab as a booster, irrespective of which vaccine they had initially.
The announcement was made by Professor Jonathan Van-Tam, the deputy chief medical officer for England, at a news briefing on Monday morning.
The JCVI is also advising that a second dose of the Covid-19 vaccine should be offered to 16 and 17-year-olds who are not in a Covid-19 at-risk group.
A second dose of the Pfizer/BioNTech jab should be given to 16 to 17-year-olds at least 12 weeks after the first, with the longer timescale believed to reduce the very small risk of a severe adverse reaction.
The vaccine committee said that the broadening of the booster campaign and the offer of a second jab to 16 and 17-year-olds will "help extend our protection into 2022".
Health Secretary Sajid Javid said the Government had accepted the JCVI's recommendation and it would "keep under review whether the booster programme should be extended to all people under the age of 40".
Health chiefs are trying to increase up take-up to avoid a coronavirus crisis this winter which could overwhelm the NHS.
Research so far has shown that a Pfizer booster after two doses of the AstraZeneca vaccine has an effectiveness of 93 per cent against symptomatic Covid-19.
For individuals who had Pfizer for the first and second dose and then a Pfizer booster it is 94 per cent.
The risk of hospitalisation or death from Covid-19 after a booster is expected to be even smaller.
Dr June Raine, chief executive of the Medicines and Healthcare products Regulatory Agency, said: "Our safety monitoring to date shows that Covid-19 vaccines continue to have a positive safety profile for the majority of people.
"The vast majority of reactions which are reported relate to expected side-effects such as injection site reactions and flu-like symptoms, as was seen in our initial assessment.
"Our proactive monitoring of the safety of booster doses does not raise any new concerns."
On Monday, Conservative Party co-chairman Oliver Dowden urged people to get their booster jabs "when the call comes" if they wanted to avoid curbs over the Christmas period.
He said: "If you get the booster when the call comes that is the biggest wall of defence that we have against Covid.
"I am confident that if we stick the course, people take the boosters when they are asked to do so, that vaccine wall will hold up and we will be able to have a decent Christmas this year."
Before the announcement on Monday, people aged 50 and over, those living and working in care homes, frontline health and social care works and younger people at risk have been eligible for a booster jab six months after their second dose.
The booster programme has formed part of the Government's 'Plan A' for managing Covid-19 over the autumn and winter period, in a bid to reduce case numbers without resorting to stricter coronavirus measures.
Some 12.6 million people have had a third Covid-19 jab so far, according to official figures.
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