Vaccine effectiveness against Omicron

The researchers found a significantly increased risk of developing a symptomatic Omicron case compared to Delta for those who were two or more weeks past their second vaccine dose, and two or more weeks past their booster dose (for AstraZeneca and Pfizer vaccines).

Depending on the estimates used for vaccine effectiveness against symptomatic infection from the Delta variant, this translates into vaccine effectiveness estimates against symptomatic Omicron infection of between 0% and 20% after two doses, and between 55% and 80% after a booster dose. Similar estimates were obtained using genotype data, albeit with greater uncertainty.