A large British study looking at coronavirus infections in real life confirms what lab experiments have shown: most people keep some antibodies to the virus for at least six months after recovery.
The study also indicates 8.8% of the UK population had been infected with coronavirus by December – but almost twice as many Blacks, 16.3%, had evidence of previous infection.
The study from UK Biobank, a biomedical database and research group, measured levels of previous infection in various population groups across the UK from the end of May to the beginning of December. It showed 99% of the participants who had previously tested positive for Covid-19 retained antibodies for three months after being infected and 88% had them for six months.
“Although we cannot be certain how this relates to immunity, the results suggest that people may be protected against subsequent infection for at least six months following natural infection. More prolonged follow-up will allow us to determine how long such protection is likely to last,” Naomi Allen, UK Biobank chief scientist, told a news briefing Tuesday.
Antibodies were found in a greater proportion of younger people compared to older participants. The researchers said 13.5% of participants under 30 had detectable antibodies, while only 6.7% of those over 70 did. And 16.3% of Black volunteers in the study had antibodies to the virus, compared to 8.5% of White participants and 7.5% of participants of Chinese ethnicity.
Allen said the team did not know whether the antibodies could provide protection against new variants of coronavirus. “I think it’s just too early to tell about the level of protection,” she said. According to a report published Monday by Public Health England, the B.1.1.7 variant spreading across the UK and the world risks becoming somewhat resistant to the immune protection offered by vaccines as it continues to mutate.
Rory Collins, head of the Nuffield Department of Population Health at the University of Oxford, said Tuesday that people who had previously been infected should still take care and obey social distancing guidelines.
“We can’t be sure that [antibodies provide] complete protection,” Collins said, adding that scientists still did not know if people who had been previously infected could still carry and transmit the virus.
The study included 20,000 people who have been taking part in a range of Biobank studies, plus their adult children and grandchildren. UK Biobank collected monthly blood samples and data on potential symptoms from the group. By far the most common symptom detected by people who had once had Covid-19 were the loss of smell and taste. These symptoms were reported by 43% of participants with detectable antibodies. And 24% who tested positive had no symptoms at all.