of cases of SARS-CoV-2 infection among vaccinated adolescents, we could not adjust for weekly vaccine effectiveness evaluation. However, adjustments for sex and epidemiologic week for days 8–28 after the second dose combined demonstrated adjusted vaccine effectiveness of 91.5% (95% CI 88.2%–93.9%) against SARS-CoV-2 infection (Table). We did not estimate vaccine effectiveness against symptomatic diseases because epidemiologic investigation was performed for 42% of vaccinated and 40% of unvaccinated adolescents in our cohort. As of August 26, 2021, none of the vaccinated adolescents who became SARS-CoV-2–positive on days 1–28 after the the second vaccine dose had been hospitalized. By that same date, among unvaccinated adolescents, 7 (0.38%) of 1,825 who tested positive for SARS-CoV-2 on days 1–7 after vaccinated adolescents had received their second vaccine dose and 26 (0.32%) of 8,144 who tested positive on days 8–28 were hospitalized. Also by August 26, no vaccinated or unvaccinated SARS-CoV-2–positive adolescents had died. Conclusions The BNT162b2 vaccination campaign for adolescents 12–15 years of age in Israel coincided with the outbreak of the SARS-CoV-2 Delta variant. As such, the timing enabled estimation of vaccine effectiveness against SARS-CoV-2 infection for this age group during predominant circulation of the Delta variant. Our results demonstrate high vaccine effectiveness against SARS-CoV-2 infection in this population starting the second week after the second vaccine dose. These estimates are somewhat lower than those that had been estimated for persons 16–39 years of age during the same time intervals after the second vaccine dose during circulation of the SARS-CoV-2 Alpha variant and wild-type virus in Israel (8). Specifically, adjusted vaccine effectiveness against SARS-CoV-2 infection for persons 16–39 years of age was 93.2% (95% CI 91.9%–94.2%) at 8–14 days, 96.7% (95% CI 95.8%–97.4%) at 15–21 days, and 96.6 (95% CI 95.7%–97.3%) at 22–28 days after receipt of the second vaccine dose. Although vaccine effectiveness estimates and 95% CIs during the circulation of the Alpha variant and the wild-type virus were adjusted for age, sex, and epidemiologic week, only minor differences in point estimates and 95% CIs were noted between crude and adjusted vaccine effectiveness (8). The effectiveness estimate of 55.3% in the first week after the second dose probably reflects the effect of the first vaccine dose. This estimate is consistant with previous estimates of vaccine effectiveness 14–20 days after the first dose (8–10). Our findings are consistent with those of a recent study from the United Kingdom, which demonstarated vaccine effectiveness of 88.0% (95% CI 85.3%–90.1%) against symptomatic disease caused by the SARS-CoV-2 Delta variant (11), compared with vaccine effectiveness of 93.7% (95% CI 91.6%–95.3%) against disease caused by the Alpha variant among persons >16 years of age who had received 2 doses of BNT162b2 (11). However, that study addressed neither the interval between the 2 doses nor the exact interval between assessment of vaccine effectiveness and the date of the second dose (11). As of September 2021, two controlled studies had assessed vaccine efficacy in adolescents, without specifying the SARS-CoV-2 variant (12,13). One study reported BNT162b2 vaccine efficacy of 100% against laboratory-confirmed COVID-19 >7 days after receipt of the second vaccine dose at 21 days