A previous COVID-19 infection may offer less protection against future symptomatic infections from omicron compared to other variants, according to research published Feb. 9 in The New England Journal of Medicine.
Researchers from Weill Cornell Medicine-Qatar in Doha conducted the study. To estimate protection levels from past infection, they analyzed data on COVID-19 testing, vaccination, infections, hospitalizations, deaths and patient demographics collected in national databases since the start of the pandemic.
A previous infection was 56 percent effective at preventing reinfection from omicron, compared to 92 percent for delta, 90.2 percent for alpha and 85.7 percent for beta, researchers estimated.
"Such protection against reinfection with the omicron variant was lower (approximately 60 percent) but still considerable," they said.
No reinfections caused critical or fatal COVID-19 cases. A previous infection was 87.8 percent effective at preventing severe, critical or fatal cases against omicron, 69.4 percent against alpha, 88 percent against beta and 100 percent against delta.
"The protection of previous infection against hospitalization or death caused by reinfection appeared to be robust, regardless of variant," researchers said.
View the full study here.