People who have had COVID-19 are very likely to be immune to it for at least five months, but there is evidence that those with antibodies can still carry and spread the virus, according to a study by British healthcare workers.
Preliminary findings from Public Health England (PHE) scientists showed that reinfections in people who have COVID-19 antibodies from a past infection are rare, with only 44 cases found among 6,614 people previously infected in the study.
But experts warned that the findings mean that now people who contracted the disease during the first wave of the pandemic during the early months of 2020 could be vulnerable to catching it again.
They also warned that people with so-called natural immunity (acquired by having had the infection) can still carry the SARS-CoV-2 coronavirus in their nose and throat and unwittingly can transmit it.
“We now know that most people who have had the virus and developed antibodies are protected against reinfection, but that’s not total and we still don’t know how long the protection lasts,” said Susan Hopkins, senior PHE medical advisor and co- study leader, whose findings were released Thursday.
“This means that even if you think you already have the disease and are protected, you can be sure that you are very unlikely to develop serious infections. But there is still the risk that you may acquire an infection and pass it on to others. “.
Main implications
Experts not directly involved in the research, known as the SIREN study, urged people to take note of their main findings.
“These data reinforce the message that, at the moment, everyone is a potential source of infection for others and should behave accordingly,” said Eleanor Riley, a professor of immunology and infectious diseases at the University of Edinburgh. .
Simon Clarke, an associate professor of cell microbiology at the University of Reading, said the study “has important implications for how we can get out of the current crisis.”
“This means that the vast majority of the population will need to have natural immunity or be vaccinated so that we can fully lift the restrictions on our lives, unless we are prepared to see that there are more people infected and dying of COVID-19.” . He said.
PHE said in a statement that the study had not been able to scan for antibodies or other immune responses to COVID-19 vaccines that were being rolled out in Britain. The effects of vaccines as part of SIREN were studied later this year.
The SIREN study includes tens of thousands of British healthcare workers who have been tested regularly since June to detect new COVID-19 infections and the presence of antibodies.
Between June 18 and November 24, the scientists found 44 possible reinfections, two “likely” and 42 “possible,” among 6,614 participants who had tested positive for antibodies. According to them, this represents 83% protection against reinfection.
The researchers said they would continue to follow participants to see if this natural immunity could last more than five months in some. But they said early evidence from the next stage of the study suggested that some people with immunity could still carry high levels of the virus.
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