‘Natural Immunity’ Holds Up Against Severe Omicron Cases in Qatar Study

Prior SARS-CoV-2 infection was estimated to be less effective at preventing reinfection with the Omicron variant compared to prior variants, though it did appear to hold up against severe disease, researchers in Qatar found.

The effectiveness of previous infection in preventing reinfection was estimated at 56.0% (95% CI 50.6-60.9) against the Omicron variant, as compared to 90.2% (95% CI 60.2-97.6) against the Alpha variant, 85.7% (95% CI 75.8-91.7) against the Beta variant, and 92.0% (95% CI 87.9-94.7) against the Delta variant, reported Laith Abu-Raddad, PhD, of Weill Cornell Medicine Qatar in Doha, and colleagues.

However, no reinfections resulted in death, and effectiveness of natural infection against “severe, critical or fatal” COVID from the Omicron variant was 87.8% (95% CI 47.5-97.1), they wrote in a correspondence in the New England Journal of Medicine.

The authors noted that because Omicron “harbors multiple mutations that can mediate immune invasion,” they wanted to examine how effective prior infection was at preventing symptomatic new COVID cases.