COVID-19 infection confers some immunity, but virus can still spread, study finds

LONDON (Reuters) – People who have had COVID-19 are very likely to be immune to the virus for at least five months, but there is evidence that those who have antibodies may still be able to carry and spread the virus. virus, a study on British health care workers has found.

Preliminary results from scientists at Public Health England (PHE) have shown that re-infections in people who have COVID-19 antibodies from a previous infection are rare – with just 44 cases found among 6,614 people previously infected in the study.

But experts have warned that the results mean people who contracted the disease in the first wave of the pandemic in the early months of 2020 may now be vulnerable to contracting it again.

They also warned that people with so-called natural immunity – acquired after having the infection – might still be able to carry the SARS-CoV-2 coronavirus in their nose and throat and could pass it unintentionally.

“We now know that most of those who have had the virus and have developed antibodies are protected against reinfection, but it is not total and we do not yet know how long the protection lasts,” said Susan. Hopkins, senior medical advisor at PHE and co-leader of the study, the results of which were released Thursday.

“This means that even if you think you have had the disease before and are protected, you can be reassured that you are very unlikely to develop serious infections. But there is always a risk of getting an infection and passing it on to others. “

MAJOR IMPLICATIONS

Experts not directly involved in the research, known as the SIREN study, urged people to take note of its 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, professor of immunology and infectious diseases at the University of Edinburgh.

Simon Clarke, associate professor of cell 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 either need to have natural immunity or have been immunized for us to completely lift the restrictions on our lives, unless we are prepared to see many more people infected and die from COVID.” -19, ”he said.

PHE said in a statement that the study was unable to explore for antibodies or other immune responses to COVID-19 vaccines being deployed in Britain. The effects of the vaccines will be investigated under SIREN later this year, he said.

The SIREN study involves tens of thousands of healthcare workers in Britain who have been tested regularly since June for new COVID-19 infections 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 had tested positive for antibodies. This represents an 83% protection rate against reinfection, they said.

The researchers said they would continue to follow the participants to see if this natural immunity might last longer than five months in some. But they said early evidence from the next stage of the study suggested that some immune people may still be carriers of high levels of the virus.