Booster vaccines for Covid-19 are set to be rolled out alongside flu jabs to over-50s from September, amid fears both viruses could make a winter comeback.
Health officials said the relaxation of restrictions was "heavily dependent" on the continued success of the jabs programme, as they set out details of the likely schedule this winter.
Under the plans, more than half the population will be offered Covid-19 boosters at the same time as their flu jab.
Details of the programme have yet to be agreed, with trials ongoing, but it could mean one jab in each arm at the same time.
In interim advice, the Government’s joint committee on vaccination and immunisation (JCVI) has said the rollout should start with those who were in the first four priority groups.
This means everyone over 70, and health and care workers, could start being offered the jab from September, as the rollout of first doses is completed.
The programme will then continue to all over-50s, and everyone who was in the first nine priority groups for the first jabs, expanding the criteria, so that all adults eligible for flu jabs can also have a Covid-19 booster.
A final decision will be taken later this summer, but health officials are preparing to roll out the programme for both jabs simultaneously, starting in September.
It comes amid fears that Britain could face a particularly bad flu season because of the reduced social contact last winter, limiting the build up of immunity.
Officials said the rollout this winter would focus on those in priority groups, but did not rule out expanding booster jabs to all adults when all over-50s were covered.
Key to freedom
Professor Jonathan Van-Tam, the deputy chief medical officer for England, said: "Where the UK has reached so far on vaccination is truly fantastic.
"But we need to keep going and finish giving second doses to those remaining adults who have not had them; this is the best thing we can do to prevent the disease from making a comeback which disrupts society later in the year."
He said: "Being able to manage Covid-19 with fewer or no restrictions is now heavily dependent on the continued success of the vaccination programme.
"We want to be on the front foot for Covid-19 booster vaccination to keep the probability of loss of vaccine protection due to waning immunity or variants as low as possible. Especially over the coming autumn and winter."
He said the relaxation of restrictions could fuel a resurgence in flu this winter, suggesting that high vaccine uptake was key to keeping freedoms in place.
Prof Van-Tam added: "Fewer or no restrictions will mean that other respiratory viruses, particularly flu, will make a comeback and quite possibly be an additional problem this winter, so we will need to ensure protection against flu as well as maintaining protection against Covid-19."
Officials said decisions had yet to be taken about which vaccines were given.
Trials are examining a "mix and match" approach which could mean those given the AstraZeneca jab receive a Pfizer booster, or vice versa.
Alternative vaccines which have yet to be authorised by regulators could also be included in the rollout.
Under the plans, booster jabs will first be offered from September to those who were in the first four priority groups in the original rollout.
This means all adults aged 70 years or over, residents of care homes for the elderly, frontline health and social care workers, and those aged 16 years and over who are immunosuppressed.
During the autumn and winter, the programme will then shift to all remaining adults over the age of 50, as well as anyone aged 16 and over with the kinds of health conditions, such as asthma, which make them eligible for flu jabs.
Adult household contacts of immunosuppressed individuals, those who have a weakened immune system, will also be offered booster jabs at this stage.
Officials said the final JCVI advice would be published before September and would take into account additional scientific data from ongoing trials and real-time surveillance of the effectiveness of the vaccines over time and emerging variants.
The final advice could change from the interim advice as further data is analysed.
Sajid Javid, the Health and Social Care Secretary, said: "The phenomenal vaccine rollout has already saved tens of thousands of lives and prevented millions of infections, helping to wrestle back control of the pandemic and ease lockdown restrictions so we can return to normal as soon as possible.
"We welcome this interim advice, which will help us ensure we are ready in our preparations for autumn. We look forward to receiving the committee’s final advice in due course.
“We need to learn to live with this virus. Our first Covid-19 vaccination programme is restoring freedom in this country, and our booster programme will protect this freedom.
"We are working with the NHS to make sure we can rapidly deliver this programme to maintain protection for people in the winter months."
Officials said there was good evidence that two doses of any Covid-19 vaccine would protect against severe disease for at least six months for most people, and said it may last longer in younger people.
As most younger adults would receive their second Covid-19 vaccine dose in late summer, the benefits of booster vaccination in this group would be considered by the JCVI at a later time when more information was available, they said.
Nadhim Zahawi, the Vaccines Minister, said: "Our Covid-19 vaccination programme has been a roaring success, with almost 85 per cent of adults across the UK receiving a first dose and more than 62 per cent getting both doses.
"We are now planning ahead to future-proof this progress and protect our most vulnerable from variants and flu ahead of the winter.
"Vaccines are the best way to stay on top of this virus and I urge everybody to take up the offer as soon as possible."