A scientific adviser has claimed a third of the population in England will still be vulnerable to being infected with the Delta variant of Covid-19.
Professor Matt Keeling, from the University of Warwick, estimates there will have been 15.3 million symptomatic and asymptomatic infections in the country by July 19 - the date the government has confirmed they will lift social contact restrictions.
This number will mean that 27.4% of the population in England will have been infected and therefore have natural immunity, leaving the rest either vaccinated or unvaccinated.
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When taking account of vaccines, the modellers at Warwick have calculated that 33% of the population in England will remain susceptible to the Delta variant of Coronavirus.
Professor Keeling told a briefing: "There's still a large number of susceptibles out there and we expect infection, cases and hospital admissions to keep increasing between now and July 19th."
The professor - who is also a member of Scientific Pandemic Influenza Group on Modelling (Spi-M), which informs ministers - backed calls for people to take it slowly when restrictions are released as keeping hospital admissions low "and below what we saw in January" really does rely on individual behaviour.
He added experts do not yet know about drops in immunity in any great detail and "any waning immunity" could alter the figures, pushing up cases.
He said: "You almost need to think of this like a spring-like system, and, if you suddenly release it, you get a much, much bigger wave than if you gradually let things change."
Professor Graham Medley, from the London School of Hygiene and Tropical Medicine and a member of the Scientific Advisory Group for Emergencies (Sage), told the briefing he thinks the country will reach the herd immunity threshold "one way or another".
At that point, the reproduction number (the R) will be around 1 and "that is herd immunity", he added.
Prof Medley said he agrees the UK will always experience a wave of infection when it releases restrictions "because the vaccines are not perfect and we're not vaccinating everybody, so there is room for another wave of infection".
He said: "That's going to be the case for all countries, not just this one."
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