Covid-19 immunity levels in the public could be as high as 30 per cent, according to a new international study.
Researchers at the Karolinska Institutet in Sweden found that people with mild or no symptoms had developed “T-cell” immunity — despite testing negative for antibodies that fight the novel disease.
“Our results indicate that roughly twice as many people have developed T-cell immunity compared with those who we can detect antibodies in.”
Professor Danny Altmann, British Society for Immunology spokesperson and Professor of Immunology at Imperial College London, said: “Among the many studies of cellular (T cell) immunity to SARS-CoV-2 that have appeared in the past few months, this is one of the most robust, impressive and thorough in the approaches used.
“It adds to the growing body of evidence that many people who were antibody-negative actually have a specific immune response as measured in T cell assays, confirming that antibody testing alone under-estimates immunity.
He added: “So far, there is a sense from some studies that functional, virus-neutralising antibody is one such correlate of protection. We urgently need experimental studies to help confirm whether T cell immunity alone can give protection.”
A UK study published by the Office for National Statistics last month suggested that one in 20 people in the UK (5 per cent) had been infected with Covid-19. For London, the figure was one in six (17 per cent).
Earlier this week, Leicester was placed on lockdown following a surge in infections, with experts warning that more local shutdowns could be enforced if people flouted social distancing guidelines.
Sweden, one of the few countries in the world not to impose a lockdown, has recorded more than 68,000 cases but less than 6,000 deaths.