Quote:Antibody tests on random samples of the population have so far shown much lower levels of general infection than the government’s scientific advisers claimed would be necessary to attain ‘herd immunity’. In London, for example, tests have shown that 17 per cent of the population have antibodies to Sars-CoV-2, the virus that causes Covid-19. In New York, the figure is 21 per cent. At the beginning of this crisis, on the other hand, Sir Patrick Vallance, the chief scientific adviser, suggested that at least 60 per cent of the population would have to be infected in order to achieve herd immunity.

But are antibodies the whole story? Not according to a team from Sweden’s Karolinska Institute, which has found that 30 per cent of Swedish blood donors in May this year were found to have an immune response to Covid-19 in their T cells – white blood cells that are an essential part of the immune system. Remarkably, many of these people had no detectable antibodies – suggesting that their T cells had fought off the disease without any need to produce antibodies. In all, they say, roughly twice as many people had a T cell reaction than had measurable levels of antibodies.