People who have already contracted coronavirus are as protected against reinfection as those who have received the best Covid-19 vaccines, according to a survey of 20,000 British healthcare workers, the largest study in the world to date.
Public Health England regularly tested two groups of matching volunteers between June and November: 6,000 health workers who had previously been infected with coronavirus and 14,000 who had not.
A comparison of infections in the two groups, described in preliminary results released Thursday, found that a previous infection provided at least 83% protection against reinfection. It gave greater than 94% protection against symptomatic Covid-19, which matches the numbers for the most effective Covid-19 vaccines.
Susan Hopkins, PHE’s senior medical advisor, said she was “strongly encouraged” by the finding that the infection offered potent – but not complete – protection against reinfection for at least five months.
“A natural infection is as good as a vaccine, which is very good news for the population,” she said.
Although the study could not provide data on possible protection beyond five months, Professor Hopkins was optimistic it would last “much longer than the few months people speculated” during the early stages of the disease. pandemic last year.
“This will give a level of immunity in the community which will reduce transmission,” she said.
During the study, 44 people in the previously infected group of 6,000 people tested positive at least three months apart, suggesting they had been “potentially re-infected.” But since genomic analysis was not available to confirm that different viruses were responsible for the two infections, they were not considered to be confirmed re-infections. The same virus may have been incubated for a long time in the same individual, although the researchers thought this was less likely in most cases.
Eleanor Riley, professor of virology at the University of Edinburgh, said data from the study also suggested that people who had recovered from Covid-19 were less likely to pass the virus on to others without it. namely, because natural infection appeared to provide about 75% protection against asymptomatic reinfection. “This is good news in terms of long term trends for the pandemic,” she said.
Yet Professor Hopkins urged people “not to misunderstand these early findings.”
“If you think you have had the disease before and are protected, you can be reassured that you are very unlikely to develop a serious infection, but there is always a risk that you could get an infection and pass it on. to others, ”she said.
The cut-off point for preliminary analysis in late November came too early for researchers to examine how well the vaccines – the first of which was approved for use in the UK in December – have protected the group’s health workers study.
Researchers were also unable to assess the impact of the new, more contagious B.1.1.7 variant on reinfection rates. PHE aims to expand the research project over the next three months to include 100,000 health workers and examine these two questions.