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 can still carry and spread the virus, a study among UK health workers found.
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 have warned 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 vulnerable again to catching it.
They also warned that people with the so-called natural immunity – obtained through infection – could possibly 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 get serious infections. But there is still a risk that you could get an infection. and can pass it on to others. “
Important implications
Experts not directly involved in the research, known as the SIREN study, asked people to take note of its key findings.
“This data reinforces the message that for the time being, everyone is a possible source of infection for others and should act accordingly,” said Eleanor Riley, a professor of immunology and infectious diseases at the University of Edinburgh.
Simon Clarke, an associate professor of cellular microbiology at the University of Reading, said the study “has major implications for how we can emerge from the current crisis.”
“This means that the vast majority of the population will have to have natural immunity or that it will have to be vaccinated for us to completely lift the restrictions on our lives, unless we are prepared to see many more people become infected and die. to COVID-19, “he said.
PHE said in a statement that the study could not investigate antibodies or other immune responses to the COVID-19 vaccines being rolled out in Britain. The effect on vaccines will be studied later this year as part of SIREN.
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 found 44 potential re-infections – two “probable” and 42 “possible” – among 6,614 participants who tested positive for antibodies. That’s an 83% protection rate against re-infection, they said.
The researchers said they will continue to follow the participants to see if this natural immunity can last longer than five months in some cases. But they said early evidence from the next phase of the study suggested that people with immunity could still carry high levels of viruses.
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