Sars could provide key to Vietnam’s virus resistance

SCIENTISTS in Asia are investigating whether countries with a frequent circulation of Sars-like viruses may have higher levels of generalised immunity among the population – a theory that, if proven, could help health authorities manage the Covid-19 pandemic.

The idea has been floated by medical experts including John Bell, a professor of medicine at the University of Oxford, who recently suggested that nations like Vietnam had avoided a flood of cases without a total lockdown because its citizens were not immunologically “naive”, as it was assumed.

This could mean that the regular existence of other Sars-like viruses had resulted in more natural resistance.

Until last weekend, Vietnam, a country of 95million that neighbours China, had eliminated local transmission for 99 days. The authorities are now battling an outbreak that has spread through the coastal resort of Da Nang. The first two Covid-19-related deaths were recorded on Friday, but the national case count still remained low, at 586, as of yesterday.

Prof Guy Thwaites, the director of the Oxford University Clinical Research Unit in Ho Chi Minh City, attributed Vietnam’s earlier success to its “extraordinary” response.

“In Vietnam, they responded very quickly, they were able to track the first people coming into the country with it… [they were] all isolated, contacts all isolated,” he said. “They quarantined more than 200,000 people over a period of four months, even with relatively small numbers of cases.”

The idea of generalised immunity was “an entirely reasonable hypothesis”, Prof Thwaites said.

Scientists in Singapore, which, similarly to Vietnam, was badly hit by Sars in 2003, are already actively exploring the idea.

Prof Antonio Bertoletti, a specialist in infectious diseases at the Duke-NUS Medical School, led a research team that recently uncovered the presence of virus-specific T-cell immunity in people who recovered from Covid-19 and Sars, as well as some who had never been infected by either virus, suggesting a level of pre-existing immunity in the general population.