Covid reinfection for people who had the virus is not likely to happen for at least six months, according to a new Oxford study.
Researchers find the results “exciting” because they signify a crucial step in determining how Covid-19 immunity may work.
The study, which claims to be the first large-scale research on Covid reinfection, was part of a collaboration between the University of Oxford and Oxford University Hospitals NHS Foundation Trust. However, it has not yet been peer-reviewed.
The researchers worked on the study in a 30-week period between April and November with 12,180 health-care workers at Oxford University Hospitals.
The participants were tested for antibodies to the virus that brings Covid-19 as a way of identifying who had previously been infected. They underwent testing for Covid-19 when they manifested symptoms and as part of regular testing.
According to the study, 89 of 11,052 employees without antibodies showed a new infection with symptoms. None of the 1,246 staff with antibodies had a symptomatic infection. Staff with antibodies were less likely to test positive for the coronavirus without symptoms.
“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,” said professor David Eyre of the University of Oxford’s Nuffield Department of Population Health.
Moreover, researchers said the health workers who did not show antibodies against Covid were found to be more likely to have the infection.
They explained that there was not yet sufficient data to come up with a conclusion about the protection from the initial infection beyond a six-month period. The researchers will resume data gathering to understand how long protection from reinfection can last.
“This is an exciting finding, indicating that infection with the virus provides at least short-term protection from re-infection — this news comes in the same month as other encouraging news about COVID vaccines,” said Dr. Katie Jeffery, director of infection prevention and control for Oxford University Hospitals.
The findings come after the announcements of encouraging vaccine development results over the past weeks, particularly those from Pfizer-BioNTech and Moderna, as well as promising phase two results from AstraZeneca-Oxford.
However, public health authorities and experts warned that the distribution of a safe and effective vaccine could take months or more than a year, reach so-called herd immunity and contain the virus.
The study also revealed that antibody levels peak lower and fall faster in younger adults.
“We know from a previous study that antibody levels fall over time,” Eyre said, referencing the research published earlier this month.
“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.”