People previously infected with Covid-19 are ‘highly unlikely’ to contract the illness again for at least six months, a study at Oxford University has discovered.
In the first trial to judge whether antibodies actually prevent people from getting the virus for a second time, researchers tracked 12,180 healthcare workers, of whom roughly 10 per cent had caught coronavirus.
In the six months of follow up, nobody who had been infected previously was diagnosed with symptomatic Covid-19 for a second time compared with 89 people who had never had the disease.
Just three people who had previously been infected tested positive again for the illness, but none has symptoms and all said they still felt well.
Professor David Eyre of the University of Oxford’s Nuffield Department of Population Health, said: “This is really good news, because we can be confident that, at least in the short term, most people who get Covid-19 won’t get it again.
“We know from a previous study that antibody levels fall over time, but this latest study shows that there is some immunity in those who have been infected.
“We will continue to follow this cohort of staff carefully to see how long protection lasts and whether previous infection affects the severity of infection if people do get infected again.”
The study was carried out on staff from Oxford University Hospitals (OUH) NHS Foundation Trust between April and November.
Out of 55 million cases globally, there have been just 10 confirmed cases of reinfection.
Previously it was feared antibodies wane after just a couple of months but a number of recent studies have shown both T-cells and antibodies last for at least six months, meaning those who have recovered from an infection are protected for at least that amount of time.
It is also good news for immunisation programmes, because if the body can provoke a long-term immune response naturally, it should also do so when triggered by a vaccine.
The hospital tested staff regularly for Covid-19, both when they became unwell with symptoms and also as part of regular testing of well staff.
The researchers then followed whether staff who had been infected before had the same number of new Covid-19 infections as those who had not been infected before.
Dr Katie Jeffery, director of infection prevention and control for Oxford University Hospitals said: “This is an exciting finding, indicating that infection with the virus provides at least short-term protection from reinfection – this news comes in the same month as other encouraging news about Covid-19 vaccines.”