HealthDay News — The omicron BA.2 subvariant seems to be less severe than the delta variant and the original omicron variant, according to a study published online October 25 in JAMA Network Open.

Zachary H. Strasser, MD, from Massachusetts General Hospital in Boston, and colleagues conducted a retrospective cohort study that applied an entropy balancing approach to compare the adjusted risks of mortality, hospitalization, intensive care unit admission, and invasive ventilation between the BA.2 subvariant and the omicron and delta variants after accounting for confounding variables. Data were included for 102,315 confirmed COVID-19 cases, including 20,770 labeled as delta variants, 52,605 as omicron B.1.1.529 variants, and 28,940 as omicron BA.2 subvariants.

The researchers found that the mortality rates were 0.7, 0.4, and 0.3% for delta, omicron B.1.1.529, and omicron BA.2, respectively. The adjusted odds ratio of mortality was 2.07 and 2.20 for the delta variant and for the original omicron variant, respectively, compared with the omicron BA.2 subvariant. The omicron BA.2 subvariant was significantly less severe for all outcomes than the omicron and delta variants.

“While the SARS-CoV-2 virus always has the potential to mutate to a more deadly form, when you look at the recent trajectory of delta, omicron BA.1, to omicron BA.2, the virus seems to be getting intrinsically less severe,” Strasser said in a statement. “Hopefully this trend will continue.”

Abstract/Full Text