Almost all people previously infected with COVID-19 have high levels of antibodies for at least six months that are likely to protect them from reinfection, a UK study shows.
Scientists say the research, which measured levels of previous COVID-19 infection in British populations, as well as how long antibodies persist in those infected, should reassure 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, chief scientist at the UK Biobank, where the study was conducted.
Among participants who had tested positive for previous COVID-19 infection, 99 per cent retained antibodies to SARS-CoV-2 for three months, the results showed.
After the full six months of follow-up in the study, 88 per cent still had them.
"Although we cannot be certain how this relates to immunity, the results suggest people may be protected against subsequent infection for at least six months following natural infection," Allen said.
She said the findings were also consistent with results of other studies in the United Kingdom and Iceland which found antibodies to the coronavirus tended to persist for several months in those who have had the disease and recovered.
A study of UK healthcare workers last month found people who have had COVID-19 were likely to be protected for at least five months but noted those with antibodies may still be able to carry and spread the virus.
The UK Biobank study also found the proportion of the UK population with COVID-19 antibodies - a measure known as seroprevalence - rose from 6.6 per cent at the start of the study period in May/June 2020 to 8.8 per cent by November/December 2020.
SARS-CoV-2 seroprevalence was most common in London, at 12.4 per cent, and least common in Scotland at 5.5 per cent.