One vaccine appears to be the most effective after the first dose.
A new study regarding the effectiveness of COVID-19 vaccines against variants of concern was released on July 3, 2021.
The preprint study, which has not undergone peer review, was conducted in Ontario and looked at the Pfizer, Moderna, and AstraZeneca vaccines in relation to the four variants of concern (VOCs) detected in Ontario: Alpha (B.1.1.7), Beta (B.1.351), Gamma (P.1), and Delta (B.1.617.2).
The study suggests that "even a single dose of these 3 vaccine products provide good to excellent protection against symptomatic infection and severe outcomes caused by the 4 currently circulating VOCs."
It also said that "2 doses are likely to provide even higher protection." While reports on vaccines' effectiveness against VOCs have varied, this study suggests that the vaccines are doing their job.
The study showed that two doses of the Pfizer vaccine provided roughly the same protection against each of the four variants.*
It also seems that Moderna is more effective after just one dose compared to Pfizer and AstraZeneca, according to the study.
Health Canada has a robust website with all the latest information on COVID-19 vaccines and can answer any questions you may have.
*This article has been updated.