People who recovered from COVID-19 are at little risk of contracting the disease again, according to a study published this week.
Researchers in Qatar examined a cohort of over 353,000 people using national databases that contain information about patients with polymerase-chain-reaction-confirmed infections.
The studied population contracted COVID-19, the disease caused by the coronavirus or SARS-CoV-2, between Feb. 28, 2020, and April 28, 2021. Reinfections were counted if a person tested positive at least 90 days after their first infection.
After excluding approximately 87,500 people with a vaccination record, researchers found those with immunity from having recovered from COVID-19 had little risk of reinfection and severe cases of the disease.
Just 1,304 reinfections were identified. That means 0.4 percent of people with natural immunity and without a vaccination record got COVID-19 a second time.
The odds of severe disease were 0.1 percent that at primary infection, according to the study. Just four such cases were detected. No cases of death were recorded among those who got infected a second time.
The study was published in the New England Journal of Medicine. It was funded by Weill Cornell Medicine–Qatar, Qatar’s Ministry of Public Health, the Hamad Medical Corporation, and Sidra Medicine
The researchers, Laith Abu-Raddad with Weill Cornell Medicine–Qatar and Dr. Robert Berollini with Qatar’s Ministery of Public Health, previously assessed the effectiveness of natural immunity against reinfection as being 85 percent or greater.
“Accordingly, for a person who has already had a primary infection, the risk of having a severe reinfection is only approximately 1% of the risk of a previously uninfected person having a severe primary infection,” they 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,” they added.
“Important study showing how rare reinfection and COVID severe disease is after recovered COVID,” Dr. Monica Gandhi, an infectious diseases doctor at the University of California, San Francisco, wrote on Twitter.
The study adds to the growing body of research that indicates people who recovered from COVID-19 enjoy high levels of immunity against reinfection, and even higher protection against severe disease and death, she added.