View article

* The derived vaccine efficacies were calculated as 100×(1−[risk among vaccinated patients/risk among unvaccinated patients]), on the basis of those remaining at risk according to the specified analysis period. The vaccine efficacies reported by Polack et al. were calculated as 100×(1− IRR), where IRR is the calculated ratio of confirmed cases of Covid-19 illness per 1000 person-years of follow-up in the active vaccine group to the corresponding illness rate in the placebo group.† The values were derived with the data reported by the manufacturer in Figure 13 of the Vaccines and Related Biological Products Advisory Committee briefing document. 2