The study, done as part of a major collaboration between the University of Oxford and Oxford University Hospitals (OUH) NHS Foundation Trust, was published today as a pre-print.
Despite an estimated 51 million people infected with the virus worldwide, with high levels of transmission ongoing, reports of patients becoming re-infected after already having had COVID-19 are rare. However, up until now there have not been any large-scale studies of how much protection from re-infection people get after COVID-19.
The study, part of a major ongoing staff testing programme supported by the NIHR Oxford Biomedical Research Centre and Public Health England, covered a 30-week period (April – November 2020) with 12,180 health care workers employed at OUH. The health care workers were tested for antibodies to the virus that causes COVID-19 as a way of detecting who had been infected before. 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.