They warned that population immunity would not be reached in time to prevent hundreds of thousands of new infections, and called for restrictions and mask wearing to remain indefinitely.
A day later, a senior official at the World Health Organisation accused the UK of “moral emptiness and epidemiological stupidity” in pressing on with reopening on July 19.
However, far from a soaring wave of infections that could pass 200,000 a day, it looks like Britain peaked at around 60,000 cases on July 15.
Although cases rose for the first time in seven days on Wednesday, infections have decreased 36 per cent in a week, with daily figures less than half of the peak.
Scientists say they are “puzzled” by the recent drop, blaming it on the heatwave, school closures, the Euros tournament ending, or a decrease in testing. It may even be the result of the “pingdemic” causing mass isolation and lowering transmission, they say, or else people are no longer being tested for fear of missing holidays.
Few straws have been left unclutched in the bid to explain the anomaly. Yet amid the bewilderment, few seem willing to consider the prospect that it is the vaccination programme which is doing most of the heavy lifting. Britain may be finally nearing the Holy Grail of herd immunity.
Latest Office for National Statistics figures suggest that nearly 92 per cent of adults now carry antibodies to coronavirus, representing about 73 per cent of the population as a whole. Large numbers of under-18s have also now been infected, and we now know that some people are naturally immune to the virus.
University College London estimates total population immunity is now at 87 per cent, although they believe the delta variant has shifted the herd immunity threshold to 93 per cent – meaning we’re not quite there yet. With a new mutating virus, the threshold can move significantly as the disease becomes more infectious.
But being close to the threshold makes it harder for the virus to transmit, even if it does not stop it entirely.
Dr David Matthews, a virologist and expert in coronaviruses from the University of Bristol, said: “In terms of herd immunity – by which we mean the virus has managed to reach everybody and therefore most people will have a level of immune memory – I suspect we’re very close to it.
“Assuming nothing truly spectacularly leftfield happens, then this pandemic is pretty much over for the UK. I suspect we will not see a major surge this winter, or any serious levels of fatalities.
“The more we close the gap on the last 10 per cent who haven’t had the vaccine, the better we will be. Everyone will eventually meet the virus and it is far better to do so vaccinated.”
As early as July 7, Dr Meaghan Kall, an epidemiologist at Public Health England, said the antibody data suggested age groups over 24 were “very close to herd immunity” through vaccination and previous infection.
And, paradoxically, mass mixing in the Euro 2020 tournament may also have helped push the country towards nationwide protection.
“A lot of people might be disgusted by me saying this, but ultimately the Euros might turn out to be one of the things that make the rest of the summer less stressful, as we've effectively immunised a lot more younger people who wouldn't otherwise have come for or been available for a vaccine,” said Paul Hunter, a professor of medicine at the University of East Anglia.
“But I would stress that I would never suggest that as a control strategy in advance.”
Prof Karl Friston, of University College London, who believed that Britain reached herd immunity in the spring, only to lose it again with the emergence of the delta variant, said we were once again close to reaching the threshold.
“We are currently close to – but not at – herd immunity, according to real-time estimates based upon dynamic causal modelling,” he said.
“The herd immunity threshold is currently about 93 per cent but our population immunity is only 87 per cent.
“But as witnessed by the recent decline in notification rates, we do not need to reach a herd immunity threshold to bring the effective R-number below one and, in principle, suppress viral transmission.”
As always, there are caveats. The disparate nature of the epidemic means some areas could already be at herd immunity levels while others may never get there, based on localised vaccination uptake and demographics.
But it does seem that enough people are now protected that the virus is running out of steam.
We are finally reaching a point where the virus is endemic, our older population is protected, and youngsters can catch the virus safely at a time in their lives when their immune system is waiting to be primed by new diseases.
Dr Matthews added: “I’ve worked on a lot of respiratory viruses and controversially I believe this virus isn’t a killer.
“Flu kills babies and old people and it’s quite capable of killing people who have had the vaccine, but the issue here is that collectively, as a species, humans have no memory of this virus, so everyone’s immune system is starting from scratch.
“That’s ok if you’re a child but not if you’re in your 50s, 60s and 70 and relying on the memory of previous viruses.
“I think we will eventually live in a world where you will meet this virus as a kid and develop immunity early. Reaching a truce with the virus is probably where we’re heading.”