A pair of new real-world COVID-19 vaccine studies show good protection against the Delta (B1617.2) variant, one from Scotland finding higher than 90% effectiveness in preventing death in adults and the other showing 93% efficacy against symptomatic infection in Israeli adolescents after the second dose.

Overall effectiveness against death from Delta infections at least 14 days after the second vaccine dose was 90% (95% confidence interval [CI], 83% to 94%) for Pfizer and 91% (95% CI, 86% to 94%) for AstraZeneca.

In Israel, the Clalit Research Institute, in conjunction with Harvard University, conducted an observational study involving 130,464 COVID-19–naïve adolescents aged 12 to 18 years, half of whom were vaccinated with the Pfizer COVID-19 vaccine from Jun 8 to Sep 14, 2021; matched participants were unvaccinated.

Estimated effectiveness of the Pfizer vaccine against infection was 59% (95% confidence interval [CI], 52% to 65%) 14 to 20 days after the first dose, climbing to 66% (95% CI, 59% to 72%) on days 21 to 27 and 90% (95% CI, 88% to 92%) 7 to 21 days after the second dose.

Efficacy against symptomatic COVID-19 was estimated at 57% (95% CI, 39% to 71%) 14 to 20 days after the first vaccine dose, rising to 82% (95% CI, 73% to 91%) on days 21 to 27 and to 93% (95% CI, 88% to 97%) 7 to 21 days after the second dose.