For the nearly 100 million people around the world who are infected with the coronavirus, the new science offers some comfort: reinfections appear to be rare, and you can be protected against Covid-19 for at least five months.
The study, the largest of its kind, followed more than 20,000 health workers in the UK and tested them regularly for infection and antibodies. Between June and November, the researchers – from Public Health England (PHE) – found 44 potential reinfections from the 6,614 participants who tested positive for antibodies or had a previous positive PCR or antibody test when they joined the study. Meanwhile, there were 409 new infections from the more than 14,000 people who tested negative for the virus at the start of the study.
Only two of the 44 potential reinfections have been identified as “likely” and the rest are considered “possible”, “based on the amount of confirmatory evidence available”, according to the health agency. Fifteen people – or 34 percent – had symptoms.
So if all 44 reinfections are real, that means an 83 percent lower risk of reinfection compared to health professionals who have never had the virus. If only two are confirmed, the rate of protection rises to 99 percent. Either way, it suggests that natural immunity may offer a similar level of protection as the approved Covid-19 vaccines.
But as with the vaccines, it is not yet clear how long the immunity lasts after an infection. Antibodies can fade after five months or last much longer, something the researchers behind the ongoing study, which will last a total of 12 months, plan to investigate.
‘It [new] study provides some comfort that natural antibodies are quite effective in preventing reinfections, ‘Akiko Iwasaki, an immunobiologist at Yale University, told Vox. The findings are also square with another article on health workers, published in the New England Journal of Medicine in December: Researchers found that people with Covid-19 antibodies were six months better protected against the virus than people who did not have it.
Iwasaki added: “You can also interpret this data so that the protection against reinfection is not complete – especially for people who had Covid during the first wave, say in March-April 2020.”
People who have had the virus may still be able to pass it on if they are re-infected.
The good news for individuals who have had Covid-19 also comes with a warning about the risk they may still pose to other people. While antibodies may protect most people against a second case of Covid-19, early evidence from the next phase of the study indicates that some of these individuals carry high levels of viruses and may continue to transmit the virus to others. carry ‘, PHE warned in its press release.
“We now know that most of those who have had the virus and developed antibodies are protected against reinfection, but it is not total,” said Susan Hopkins, a senior medical adviser at PHE and the study leader, in a statement. statement said. and we do not yet know how long protection lasts. ”
In other words, even if you have had Covid-19, although you are unlikely to get really sick again any time soon, you should still consider yourself a potential risk of spreading it to others if you catch the virus again and are asymptomatic. . That means you still have to take precautions, such as wearing a mask and social distance, Iwasaki added. And this is one of the reasons why immunologists have said that people who are already infected with the virus are still planning to get the vaccine when their turn comes.
So there is much more to learn about immunity to Covid-19: How will the new coronavirus variants affect it? Laboratory data from South Africa, where the 501Y.V2 variant was distributed, suggest that some people were able to escape antibodies produced by previous infections.
Who most likely has a strong immune response? We do have evidence that different individuals produce different antibody responses to Covid-19 infections, but the PHE researchers found no statistically significant difference in the rate of protection between people who reported symptoms and those who did not. It is also possible factors such as gender and severity of illnesses that affect the strength of someone’s immune response.
For now, however, research suggests that survivors of the virus may only be able to help us get herd immunity faster – if their immunity lasts long enough. But since the virus has been known to humans for just over a year, it may take a while to answer the question with authority.