An international group of scientists has called on governments to overturn their coronavirus strategies and allow young and healthy people to return to normal life while protecting the most vulnerable.

The proposal drawn up by three researchers, but signed by many more, argues for letting the virus spread in low-risk groups in the hope of reaching so-called herd immunity, a situation where enough of the population is resistant to the virus to quell the pandemic.

Described in what the authors call “The Great Barrington declaration”, after the Massachusetts town where it was drawn up, the plan marks the latest round in a hotly contested debate between scientists who back radically different approaches to the crisis. One critic said it amounted to a culling of the sick and disabled, calling the idea “grotesque”.

The authors of the declaration – Sunetra Gupta at Oxford University, Jay Bhattacharya at Stanford University and Martin Kulldorff at Harvard University – argue that Covid-19 lockdowns and restrictions are producing “devastating effects” on public health by disrupting routine care and harming mental health, with the underprivileged bearing the greatest burden.

While many governments are attempting to suppress the virus until new treatments and vaccines are found, the trio write that older people and others at risk should be shielded while those in least danger should “immediately be allowed to resume life as normal”.

David Livermore, professor of medical microbiology at the University of East Anglia, and a signatory of the declaration, said older people in care homes might be protected by paying carers good salaries to live in, or in neighbouring accommodation, for a month at a time. It conceded it was harder to protect the large number of older people in the community, but suggested individuals could shield themselves. “If you’re 75 you can choose to go out as little as possible,” he said. Efforts to keep infections low, he added, “merely dragged matters out”.

The proposal follows conflicting advice sent last month from the two camps to the UK government and chief medical officers. In one open letter, Professor Gupta and her colleagues argued that suppressing the virus was “unfeasible”, while the other, headed by Professor Trish Greenhalgh, also at Oxford, said it was not practical to cut off an entire cohort of vulnerable people from open society.

William Hanage, a professor of epidemiology at Harvard, said the declaration seemed to be attacking a position of mass, ongoing lockdowns that nobody was taking. “After pointing out, correctly, the indirect damage caused by the pandemic, they respond that the answer is to increase the direct damage caused by it,” he said.

Work by Hanage and others suggests that Covid becomes more lethal than flu from the mid-30s and climbs exponentially from there, meaning that great swathes of the population, who are not in nursing homes, would need protecting. “Stating that you can keep the virus out of places by testing at a time when the White House has an apparently ongoing outbreak should illustrate how likely that is,” he said.

Another concern, he added, was that an uncontrolled epidemic among the young and healthy could leave many with long-term medical issues, the so-called “long Covid” disorders that have already affected young people.

Tweeting in response to the declaration, Gregg Gonsalves, an epidemiologist at Yale University, said shutdowns and other interventions would have to happen to get rates of infection down. With nearly half of the population having some underlying health risk for Covid-19, he said herd immunity strategies “are about culling the herd of the sick and disabled. It’s grotesque.”