By Kate Kelland
LONDON (Reuters) – People who have had COVID-19 are likely to have immunity to it for at least five months, but there is evidence that those with antibodies are still able to carry and spread the virus, a British study by found health workers.
Preliminary findings by Public Health England (PHE) scientists have shown that reinfections in people with COVID-19 antibodies from an infection are rare in the past – with only 44 cases among 6,614 people previously infected in the study.
But experts warn that the findings mean that people who contracted the disease in the first wave of the pandemic in the early months of 2020 are now again vulnerable to catching it.
They also warned that people with the so-called ‘natural immunity’ – acquired through infection – could carry the SARS-CoV-2 coronavirus in their nose and throat, and transmit it unconsciously.
“We now know that most of those who have had the virus and developed antibodies are protected against re-infection, but it is not total and we do not yet know how long protection lasts,” said Susan Hopkins, senior medical adviser at PHE and co-leader of the study, the findings of which were published Thursday.
‘This means that even if you believe you have had the disease and are protected, you can rest assured that you are highly unlikely to contract serious infections. But there is still a risk that you could catch an infection and pass it on to others. ‘
A statement from the study said the findings did not address antibodies or other immune responses to COVID-19 vaccines, or effective vaccines. Vaccinations will be responded to later this year.
The research, known as the SIREN study, involves tens of thousands of health workers in Britain who have been regularly tested for new COVID-19 infections since June, as well as for the presence of antibodies.
Between June 18 and November 24, scientists detected 44 potential reinfections – two “probable” and 42 “possible” – out of 6,614 participants who tested positive for antibodies. That’s an 83% protection rate against re-infection, they said.
The researchers plan to continue and evaluate the participants to see if this natural immunity can sometimes last longer than five months. But they warned that early evidence from the next phase of the study already suggests that some people with immunity may still carry high levels of viruses and transmit them to others.
“It is therefore crucial that everyone continues to follow the rules and stay at home, even if they have had COVID-19 before,” they said in their statement.
(Posted by Kate Kelland; Edited by Mark Heinrich)