Effectiveness of mRNA Vaccines against SARS-CoV-2 Infection
During the 17-week study period, a total of 3964 participants contributed a median of 19 unvaccinated days per participant (interquartile range, 8 to 41; total days, 127,971), during which 156 RT-PCR–confirmed SARS-CoV-2 infections were identified. A total of 3001 participants contributed a median of 22 partially vaccinated days (interquartile range, 21 to 28; total days, 81,168), during which 11 RT-PCR–confirmed infections were identified. A total of 2510 participants contributed a median of 69 fully vaccinated days (interquartile range, 53 to 81; total days, 161,613), during which 5 RT-PCR–confirmed infections were identified.
Estimated adjusted vaccine effectiveness against RT-PCR–confirmed SARS-CoV-2 infection was 91% (95% confidence interval [CI], 76 to 97) with full vaccination and 81% (95% CI, 64 to 90) with partial vaccination . Estimates of vaccine effectiveness according to mRNA vaccine product and age group are shown in
Table 2. Point estimates of vaccine effectiveness were unchanged in a sensitivity analysis that excluded periods of low local viral circulation