Ontario Vaccine Effectiveness Data

This week’s installment of Vaccines Work, Very Well brought to you by hot off the press data from Ontario by the Canadian Immunization Research Network.

Study by the Canadian Immunization Research Network on vaccine effectiveness against Delta and Omicron:

1- Booster doses significantly bumps up effectiveness against symptomatic infections even for Omicron.

2- Vaccine effectiveness against Omicron for severe outcomes held strong 6 months after two doses at 82% and increases to 95% after a booster.

Caveats with data: extends up until 26th of December. Would be difficult to get updated analyses because testing capacity maxed out and was then severely restricted as of Dec 31, 2021. Also, the first few weeks of booster doses were limited to those immunocompromised or older. Presumably vaccine effectiveness of boosters would be even higher when younger populations are included.