Beating Covid-19 provides 85% immunity, PHE study reveals

Contracting Covid-19 gives “at least as good” an immune defence against infection as a vaccine for up to five months, according to a study of 21,000 healthcare workers.

Researchers at Public Health England (PHE) found that recovered Covid patients had around 85% protection against both asymptomatic and symptomatic reinfection.

The study tracked 6,600 clinical staff infected last spring, along with 14,000 who had remained healthy, regularly testing them for Covid-19. By November, 318 infections were recorded among those who had not ever had the virus, compared to 44 reinfections. PHE also found that in the latter group, reinfection produced mild or no symptoms.

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Susan Hopkins, deputy director of the national infections service at PHE, said: “Overall I think this is good news, it allows people to feel that their prior infection will protect them from future infections, but at the same time it is not complete protection and therefore they still need to be careful when they’re out and about.”

How long such immunity lasts is an open question, with the PHE study finding that while the immunity appeared to last five months, it could fade. “The immune system’s memory is rather like our own - it remembers some infections clearly, but has a habit of forgetting others,” the BBC reports.

Researchers said that the findings are “not a licence to ignore social distancing”, The Times adds, as the immunity will wear off and you could still be infectious to others.

Last August, scientists in Hong Kong reported the “world first” case of a healthy man in his 30s who became reinfected with coronavirus almost five months after he initially contracted the disease. Scientists said genome sequencing indicated that the man had two strains of virus that were “clearly different”, the New Scientist reported at the time, apparently confirming a case of reinfection.

The British government’s chief scientific adviser, Patrick Vallance, has also previously said that while multiple infections can happen, “they’re rare”. “In any infectious disease there are cases where people can catch something again,” Vallance said. “There’s nothing to suggest that this is a common occurrence in this disease but we are learning as we go along.”