This study provides the most conclusive evidence to date that infection with the omicron subvariant BA.1 was inherently less deadly than delta when controlling for a number of key covariates. Combining death certification records with molecular surveillance is the main advantage of this study, which avoids previous biases in covid-19 death designations. Accounting for a broad array of standardised covariates, including sociodemographic variables, pre-existing health conditions, and previous immunity, is another strength.

BMJ 2022; 378 doi: https://doi.org/10.1136/bmj.o1806 (Published 02 August 2022)

Quote from the BMJ editorial. Here’s the link to the study:

Risk of covid-19 related deaths for SARS-CoV-2 omicron (B.1.1.529) compared with delta (B.1.617.2): retrospective cohort study — BMJ 2022; 378 doi: https://doi.org/10.1136/bmj-2022-070695