Immunology experts have criticised the British Government's strategy of allowing large numbers of people to become infected with coronavirus to develop "herd immunity" so that the more vulnerable do not contract the disease.
On Friday, Sir Patrick Vallance, the chief scientific adviser, said the aim was to "broaden the peak" of the illness but not suppress it, adding that if many people caught it and became immune then transmission would stop.
He suggested that around 60 per cent of Britons would need to become infected to develop herd immunity and protect those most at risk.
Yesterday UK Secretary of State for Health and Social Care Matt Hancock appeared to backtrack on the idea, stating that "herd immunity" was a "scientific concept" rather than the Government's goal or policy.
In a letter to the Health Secretary, Sir Patrick and Prof Chris Whitty, the Government's chief medical officer, the British Society for Immunology (BSI) warned there could be "severe consequences" of infecting large numbers of people when knowledge of the virus was still so limited. "We don't yet know if this novel virus will induce long-term immunity in those affected as other related viruses do not," said Arne Akbar, the society president. "Therefore it would be prudent to prevent infection in the first place."
Hancock said yesterday that ministers would "listen to all the credible scientists" as the Government faced heavy criticism for not following other countries in introducing stringent measures to prevent infection.
The Government has acted slower than many nations in ordering businesses to close and banning large gatherings to stop the spread of Covid-19.
Dr Doug Brown, the BSI chief executive, said: "We have over 4,000 members and researchers and were really quite surprised and concerned that herd immunity appeared to be the government policy."
Dr Brown said there were a "number of unknowns" regarding the virus and that scientists did not know enough about whether those who catch it would develop long term immunity.
"The common cold is a coronavirus and after three months there is no longer-term immunity to catching it again. We don't know if that will be the case here. We would like to see more social distancing measures that have been brought in in other European countries, such as limiting movement within communities and banning large scale events and more home-working.
"We should also make sure we are testing some of the most vulnerable people in the community and get them the care and support and treatment they need."
The Government is concerned that introducing "draconian" isolation measures too soon will risk fatigue, with people emerging just as the virus is peaking, placing them at greater risk.
However, most other countries have brought in isolation and quarantine measures including shutting down museums and theatres and asking people to stay indoors as much as possible.
Dr Bharat Pankhania, a senior clinical lecturer at the University of Exeter Medical School, said: "It's imperative that all people, and especially those in the 60-plus age groups with existing medical conditions (at-risk groups), consider and undertake their own risk-assessment. Now is the time for them to keep a low profile whenever possible. That is, avoid crowded places, work from home, give your social life a little break, instead consider long walks in the countryside."