People who have contracted Covid-19 are unlikely to be re-infected within six months after recovery, according to a study by the University of Oxford and the University Hospitals of Oxford.
The research, presented on Friday and yet to undergo peer reviews, is based on tests conducted between April and November 2020 on 12,180 employees of the university’s hospitals. The health workers were tested regularly to determine whether they had antibodies and to see if they had COVID-19.
“This ongoing study involving a large cohort of healthcare workers has shown that being infected with COVID-19 does offer protection against re-infection for most people for at least six months,” one of the study’s co-authors, Professor David Eyre of Oxford University’s Nuffield Department of Population Health, said in a statement.
“We found no new symptomatic infections in any of the participants who had tested positive for antibodies, while 89 of those who had tested negative (for antibodies) did contract the virus,” he added.
“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,” Professor Eyre said. “Antibody levels fall over time, but this latest study shows that there is some immunity in those who have been infected.”
A total of 1,246 of the healthcare workers tested positive for antibodies but none developed new, symptomatic, COVID-19 infections. Three health workers with antibodies tested positive for COVID-19, but all were in good health and showed no symptoms.
On the other hand, 76 employees who had no antibodies tested positive for the virus.
Over 56,872,830 infections have been officially diagnosed worldwide since the outbreak of the pandemic. At least 36,274,600 persons are considered to have recovered. Re-infections have been rare.
The researchers will pursue their study on the current cohort of health workers “to see how long protection lasts and whether previous infection affects the severity of infection if people do get infected again,” Eyre said.
Another British study released last month and conducted by the Imperial College of London and Ipsos Mori Institute showed that immunity acquired by COVID-19 survivors diminished fairly quickly, especially among asymptomatic patients, only lasting for a few months.