Coronavirus reinfection is 90 per cent less likely to land people in hospital than the first time catching the virus, research shows.
Scientists said the findings, from a study of 350,000 Covid cases, suggested that the impact became more like that of the common cold once immunity had built up.
The research, published in the New England Journal of Medicine, found that those who had previously been infected with the virus had 90 per cent lower odds of hospitalisation or death, compared with the risks from a first infection.
However, the study took place before the emergence of the delta variant.
Virus ‘could adopt a more benign pattern of infection’
The study took place in Qatar, where 40 per cent of the population had detectable antibodies for coronavirus after the first wave in March 2020.
It looked at a national cohort of more than 350,000 unvaccinated people with a confirmed infection between February 2020 and April 2021.
Scientists then compared a sample from the first group with those who caught the virus twice.
In total, 193 people out of 6,095 with “primary” infections suffered severe disease, including 28 cases that were critical and seven that were fatal.
Just 1,300 people were reinfected. Of those, only four presented severe symptoms that required hospital care. None died or ended up in a critical condition.
Dr Laith Abu Raddad, researcher from Weill Cornell Medicine, in Qatar, said: “It needs to be determined whether such protection against severe disease at reinfection lasts for a longer period, analogous to the immunity that develops against other seasonal common cold coronaviruses, which elicit short-term immunity against mild reinfection but longer-term immunity against more severe illness with reinfection.
“If this were the case with SARS-CoV-2, the virus, or at least the variants studied to date, could adopt a more benign pattern of infection when it becomes endemic”.