Analysis of the effectiveness of three vaccines to protect against symptomatic SARS-CoV-2 infection and severe outcomes caused by Alpha, Beta, Gamma and Delta variants in Ontario, Canada, suggests that a single dose provides considerable protection, two doses provide even higher protection, and effectiveness against hospitalization or death is similar to or higher than against symptomatic infection.
- Sharifa Nasreen
- Hannah Chung
- Jeffrey C. Kwong
