The UK only realised "in the last few days" that attempts to "mitigate" the impact of the coronavirus pandemic would not work, and that it needed to shift to a strategy to "suppress" the outbreak, according to a report by a team of experts who have been advising the government.
The report, published by the Imperial College COVID-19 Response Team on Monday night, found that the strategy previously being pursued by the government — dubbed "mitigation" and involving home isolation of suspect cases and their family members but not including restrictions on wider society — would "likely result in hundreds of thousands of deaths and health systems (most notably intensive care units) being overwhelmed many times over".
The mitigation strategy "focuses on slowing but not necessarily stopping epidemic spread — reducing peak healthcare demand while protecting those most at risk of severe disease from infection", the report said, reflecting the UK strategy that was outlined last week by Boris Johnson and the chief scientific adviser Patrick Vallance.
But the approach was found to be unworkable. "Our most significant conclusion is that mitigation is unlikely to be feasible without emergency surge capacity limits of the UK and US healthcare systems being exceeded many times over," perhaps by as much as eight times, the report said.
In this scenario, the Imperial College team predicted as many as 250,000 deaths in Britain.
"In the UK, this conclusion has only been reached in the last few days," the report explained, due to new data on likely intensive care unit demand based on the experience of Italy and Britain so far.
"We were expecting herd immunity to build. We now realise it’s not possible to cope with that," professor Azra Ghani, chair of infectious diseases epidemiology at Imperial, told journalists at a briefing on Monday night.
As a result, the report — which its authors said had "informed policymaking in the UK and other countries in the last weeks" — said: "We therefore conclude that epidemic suppression is the only viable strategy at the current time."
A suppression strategy, along the lines of the approach adopted by the Chinese authorities, "aims to reverse epidemic growth, reducing case numbers to low levels and maintaining that situation indefinitely".
It requires "a combination of social distancing of the entire population, home isolation of cases and household quarantine of their family members", and "may need to be supplemented by school and university closures".
An "intensive intervention package" will have to be "maintained until a vaccine becomes available (potentially 18 months or more)", the report said, painting an extraordinary picture of what life could be like in the UK for the next year and a half.
On Monday afternoon, the prime minister drastically tightened the measures imposed on the British public — signalling the UK's move to a suppression strategy.
Everyone in the UK should now stop "non-essential contact" with other people and avoid pubs, clubs, cinemas, and theatres to slow the spread of the coronavirus, Johnson announced.
Families have also been urged to stay at home together for 14 days if any member is showing symptoms of the virus — a new, continuous cough or a fever.
Johnson said that anyone in isolation should avoid leaving the house "even to buy food or essentials" and should exercise outside the house only at a safe distance from others.
A government spokesperson said: “This is a very fast-moving situation. In order to give the most robust scientific advice SAGE [the Scientific Advisory Group for Emergencies] draws upon and considers a range of evidence and views to reach its recommendations. Part of this evidence includes the latest modelling data from a number of experts. All SAGE recommendations are in line with the best current evidence. We will be publishing further evidence shortly.”