COVID survivors with natural immunity at low risk for reinfection or severe symptoms, study finds

Patients who survived COVID-19 have such strong natural immunity that their chance of reinfection or serious side effects is minimal, according to a new study published in The New England Journal of Medicine.

The study conducted by researchers in Qatar reviewed global databases for 353,000 coronavirus patients who were infected between Feb. 28, 2020 and April 28, 2021.  

The researchers excluded about 87,500 people who were vaccinated, and found of the remaining population only 1,304 got reinfected, with none requiring ICU hospitalization.

“Reinfections had 90% lower odds of resulting in hospitalization or death than primary infections,”the researchers said. “…Reinfections were rare and were generally mild, perhaps because of the primed immune system after primary infection.”

“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,” the study concluded.

The researchers said it still 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.”

Such a finding could be significant, the researchers suggested, because it could mean COVID-19 could eventually “adopt a more benign pattern of infection when it becomes endemic.”