On Monday, researchers warned that Britain was “a long, long way” from anything approaching herd immunity.
Helen Ward, professor of public health at Imperial and lead researcher, said: “I think what we’re showing is that there’s a really big challenge, which is that the immunity is declining pretty fast. In three months, we’re already showing 26% drop in antibodies.
“When you think 95 out of 100 people are unlikely to be immunized and therefore likely to be susceptible, then we are a long, long way from anything that looks like protecting the population against transmission.”
Professor Wendy Barkley, head of the Department of Infectious Diseases at Imperial, said the findings suggest that Covid is likely to work in the same way as the common cold, meaning it can be reinfected regularly.
She said: “Seasonal coronaviruses, which circulate every winter and cause the common cold, can reinfect people after six to 12 months – and we suspect that the way the body responds to infection with this new coronavirus is quite similar to that.
“We still don’t know what level of antibodies are needed in a person’s blood to protect them from SARS-CoV-2 infection or reinfection, but of course this level is crucial that you need to start understanding. Most vaccine strategies seek to produce this level, and this level will be included in whether or not a population becomes immune or not. “
Prof. Barclay warned that Britain is “miles” from herd immunity.