People who recover from COVID-19 typically have a similar level of protection against future infection for at least the first five months, according to a new study, as those who have received a COVID vaccine.
The study, carried out by Public Health England (PHE), was carried out among more than 20,000 health workers. In particular, it reveals that the immunity acquired following a previous infection with SARS-CoV-2 would offer 83% protection against reinfection, for at least 20 weeks. The results show that while people are unlikely to be re-infected soon after their first infection, it is still possible to contract the disease again and potentially spread it to other people.
” Overall I think this is good news Said Professor Susan Hopkins, PHE Senior Medical Advisor. ” This makes people think that a previous infection will protect them from future infections, but it is not total protection, so they should always be careful when they are on the move. “.
For its study, the PHE recruited healthcare workers from hospitals across the UK and divided them into two groups: those who had been infected with the coronavirus before and those who had not. Between June and November of last year, participants underwent bi-monthly PCR tests for SARS-CoV-2 as well as monthly tests to look at antibody levels in their blood.
During the five-month study, the researchers monitored infection rates in both groups. They identified 44 potential re-infections, including 13 symptomatic, among the 6,614 who would have contracted COVID-19 previously, and 318 cases among the 14,173 for which there was no evidence of past infection. Previous infection offers 94% protection against symptomatic reinfection and 75% protection against asymptomatic reinfection, the researchers conclude in the paper.
The cases are called “potential” re-infections because a detailed genetic analysis of the first and second viruses must be done to confirm re-infection. However, information on early infections was often not available … ” The immunity provides a similar effect to the Pfizer vaccine and a much better effect than the AstraZeneca vaccine, and that is reassuring to people. But we are still seeing that individuals could transmit the virus anyway, so we want to warn the public Says Hopkins. In clinical trials, two doses of the Pfizer vaccine were 95% effective, compared to 62% for two doses of the Oxford / AstraZeneca vaccine.
While this study is encouraging, it is uncertain whether the same protection applies to the elderly. In fact, the study participants were between 35 and 54 years old. This age group tends to show weaker and shorter immune responses. Another question mark hangs over the risk of re-infection from the new COVID variants spotted in the UK, South Africa, Brazil and more recently the US, an issue the PHE will examine as the study continues this year.
” What we think of the numbers is: ‘is it a glass half full or half empty?’ Says Danny Altmann, professor of immunology at Imperial College. ” For many, it may be disappointing to give precise figures on the idea that immunity to this virus is apparently so variable and so low that there is more than a 1 in 10 chance of suffering from reinfection, even at five months. Especially since it is even more so now (weak), […] more than nine months from first wave infections », He concludes.