Ministers should consider a delay to the final easing of lockdown restrictions unless a slowdown in the coronavirus vaccination programme can be reversed, the Tony Blair Institute for Global Change (TBI) says.
Boris Johnson has said he wants to return the UK to as close to normality as possible on 21 June.
But a new report says slowing down that timetable as part of a package of measures could save an estimated 15,000 lives.
Plans to scrap all limits on social contact in June should be delayed for a month until the summer school holidays, when transmission rates are expected to be lower, the TBI warns.
Ensuring the restrictions were lifted only when all adults had been offered at least one vaccine could also prevent a resurgence of the virus this summer, it says.
The delay is necessary unless ministers can return the pace of the vaccination programme to where it was in mid-March, the report says.
The TBI’s proposed package of measures also includes offering Covid-19 vaccines to teenagers, subject to regulatory approval, and achieving a 65:35 split in use between the AstraZeneca and Pfizer/Moderna jabs.
Ian Mulheirn, UK policy director at the TBI, said: “Despite the success of the vaccine rollout we’re not out of the woods yet. But the government has the power to stop a deadly third wave of the virus by expanding the vaccination programme to adolescents and bringing the final step of the easing roadmap into line with the vaccine rollout timetable. Being prepared to change the strategy could save thousands of lives and the government should ask its advisors to explore these options now.”
The stance was backed by Martin Mckee, professor of European public health at the London School of Hygiene and Tropical Medicine, who said: “The authors of the report make a compelling case for caution, based on a thorough analysis of the data. The experience of Chile should serve as a warning of the risk of relaxing restrictions too soon. The vaccination programme is very important but it is only one part of a comprehensive response to this virus.”
The report says that, despite warnings from Mr Johnson, a third wave of Covid-19 across the UK later this year is not inevitable.
Modelling for the Scientific Advisory Group for Emergencies (Sage), which advises ministers, has warned that a potential third wave could even be as serious as previous outbreaks.
However, other experts have described this as unlikely, not least because millions of people have been offered protection against the virus through vaccination.
The US and Israel are among the countries planning to extend their vaccination programmes to adolescents, if allowed to do so by regulators.
The report also says a 65:35 split in use between the AstraZeneca and Pfizer/Moderna vaccines could save lives, although real-word data appears to suggest the vaccines have similar efficacy.
Ministers have consistently rejected calls to alter their timetable.
Experts warn vaccines are not 100 per cent effective, meaning a certain number of those who have received their jabs will contract Covid-19 and end up in hospital.