FILE PHOTO: A person wearing a protective face mask undergoes the depiction of a virus outside a regional science center as the city and surrounding areas face local restrictions in an attempt to avoid localized diseases of coronovirus disease. Between (COVID-19) outbreak, 3 August 2020 in Oldham, UK. REUTERS / Phil Noble / File Photo
In previous studies, antibody levels dropped rapidly within a few months after COVID-19, raising questions about the duration of infection that infection may confer.
The new discovery may have implications for reintegration risks and vaccine sustainability, said Caries Stephenson, chief executive of Decid Genetics, the study.
To find out more about how many people in Iceland were infected with the new coronavirus, and the immune status after recovery, researchers measured antibody levels in more than 30,000 Icelanders.
Based on the results, they estimate that about 1% of the population was infected. Of that group, 56% had obtained a confirmed diagnosis after a gold-standard PCR laboratory test. Another 14% were not formally diagnosed, but were excluded after exposure to the virus. In the remaining 30%, antibody tests discovered prior infection.
Researchers reported that of 1,215 people with PCR-confirmed infections, 91% had antibody levels that increased during the first two months and then plateaued.
The results, published in The New England Journal of Medicine, focus on a homogeneous population from a single country, so the findings may not be the same in other parts of the world with diverse populations.
Still, the study shows how antibody tests can determine the true spread of infection, Stephanson said.
An editorial accompanying the study warned that it was unclear whether the recovered patients’ antibodies would protect them from re-infection.
However, it suggested that antibody testing alone could be a cost-effective alternative to infection testing, and might work better in population surveys as countries seek to reopen their economies and schools.
Reporting by Vishwada Chander in Bengaluru; Editing by Nancy Lapid and Bill Burcott