On Monday, the researchers warned that Britain is “a long, long way” from anything approaching herd immunity.
Helen Ward, a professor of public health at Imperial and the lead researcher, said: “I think what we are showing is that there is a really big challenge to that, which is that immunity is waning quite rapidly. After three months, we’ve already shown a 26 per cent decline in antibodies.
“When you think that 95 out of 100 people are unlikely to be immune, and therefore likely to be susceptible, then we are a long, long way, from anything resembling a population level protection against transmission.”
Professor Wendy Barclay, the head of the Department of Infectious Disease at Imperial, said the findings suggested Covid is likely to work in the same way as the common cold, meaning it can reinfect regularly.
She said: “Seasonal coronaviruses that circulate every winter and cause common colds can reinfect people after six to 12 months – and we suspect that the way that the body reacts to infection with this new coronavirus is rather similar to that.
“We don’t yet know what level of antibody is needed in a person’s blood to protect them from infection or reinfection from SARS-CoV-2, but of course that level is a crucial thing to begin to understand. Most of the vaccine strategies are aiming to produce that level, and that level will feed into whether or not a population becomes immune or has any level of immunity.”
Prof Barclay warned that Britain was “miles off” herd immunity.