Recovered Covid patients likely protected for at least 6 months

LONDON—Almost all people previously infected with the new coronavirus have high levels of antibodies for at least six months that are likely to protect them from reinfection with the Covid-19 agent, results of a major UK study showed on Wednesday.

Scientists said the study, which measured levels of previous coronavirus infection in populations across Britain, as well as how long antibodies persisted in those infected, should provide some reassurance that swift cases of reinfection will be rare.

“The vast majority of people retain detectable antibodies for at least six months after infection with the coronavirus,” said Naomi Allen, a professor and chief scientist at the UK Biobank, where the study was carried out.

Among participants who had tested positive for previous coronavirus infection, 99 percent retained antibodies to SARS-CoV-2 for three months, the results showed. After the full six months of follow-up in the study, 88 percent still had them.

“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,” Allen said.

Consistent with other studies

She said the findings were also consistent with results of other studies in the United Kingdom and Iceland, which found that antibodies to the coronavirus tended to persist for several months in those who have had the disease and recovered.

A study of UK health-care workers published last month found that people who have had Covid-19 were likely to be protected for at least five months, but noted that those with antibodies may still be able to carry and spread the virus.

Seroprevalence

The UK Biobank study also found that the proportion of the UK population with Covid-19 antibodies—a measure known as seroprevalence—rose from 6.6 percent at the start of the study period in May/June 2020 to 8.8 percent by November/December 2020.

SARS-CoV-2 seroprevalence was most common in London, at 12.4 percent, and least common in Scotland at 5.5 percent, it found.