IAccording to preliminary data from a study published by Public Health England of more than 20,000 UK health workers, mmune reactions to previous SARS-CoV-2 infection reduce survivors’ risk of re-infection by more than 83 percent for at least five months. The researchers warn that previously infected people may still be able to transmit the virus.
“Overall, I think this is good news,” says Imperial College London epidemiologist Susan Hopkins, a senior medical advisor to Public Health England (PHE) The guard. “It makes people feel that a previous infection will protect them from future infections, but at the same time it is not complete protection and so they still need to be careful when they are out and about.”
Between June and November last year, researchers monitored infection rates in those who were infected with the virus before June and those who had not, using monthly serological tests and PCR tests twice a month. They found 44 potential reinfections, including 13 symptomatic cases, among the 6,614 who had the virus before and 318 cases among the 14,173 who had no evidence of previous infection. The authors concluded from these results that prior exposure to SARS-CoV-2 provides 94 percent protection against symptomatic reinfection and 75 percent protection against asymptomatic reinfection.
The researchers also found that people who become re-infected can carry high levels of viral load in their nose and throat even in asymptomatic cases, which correlates with a higher risk of spreading the virus to others, Hopkins says.
“Reinfection is pretty unusual, so that’s good news,” says University of Pennsylvania immunologist John Wherry nature. “But you are not free to walk around without a mask.”
“The immunity has a similar effect to the Pfizer vaccine and a much better effect than the AstraZeneca vaccine, and that’s reassuring to people. But we still see people who might be broadcasting, so we want to be careful, ”says Hopkins The guard. In clinical trials, two doses of the Pfizer vaccine prevented infection by 95 percent compared to 62 percent with two doses of the Oxford / AstraZeneca vaccine. Pfizer’s emergency vaccine has been approved in the UK, Canada, the US, Switzerland and the EU, while the Oxford / AstraZeneca emergency vaccine has been approved in the UK, Argentina, India and Mexico.
None of the people with potential reinfections had PCR-based evidence of an initial infection, but all of them contained antibodies to SARS-CoV-2 at the start of the study that had not yet been peer-reviewed or published in a medical journal. The authors tried to measure antibodies that were specific for SARS-CoV-2, but previous studies showed that antibodies against other coronaviruses can cross-react to show a false positive result for SARS-CoV-2 antibodies, which is why the researchers these named cases “possible reinfections”.
The PHE team does not yet have enough data to understand who may be at greatest risk of re-infection. Francis Crick Institute immunologist George Kassiotis recounts nature The study participants were mostly women and mostly younger than 60 years. “This group is unlikely to have the most severe form of COVID-19,” he says, “and may not be representative of the general population. ”