The Pfzer-BioNTech vaccine effectively protected adolescents 12 to15 years of age against infection with the delta variant of SARS-CoV-2, according to a study reported on Monday in the journal Emerging Infectious Diseases.¹

Israel approved the use of the Pfizer-BioNTech vaccine for adolescents on June 2, 2021 after the US FDA had extended the authorization of the vaccine to also include adolescents 12–15 years of age. By August 26, 46% of the eligible adolescents had received one dose and 31% had received both doses of the vaccine. In June, two outbreaks of Covid were reported again predominantly driven by the delta variant.

The retrospective study from Israel analysed data from adolescents across the country, who had received the second dose of the Pfzer-BioNTech (BNT162b2) vaccine during July 1–24, 2021. The control group consisted of unvaccinated persons. The vaccine effectiveness was assessed for four weeks after the second dose; effectiveness was evaluated for each week. All those participants who had tested positive for SARS-CoV-2 on RT PCR were not included in the study, irrespective of their vaccination status.

In the vaccinated group, 124 adolescents tested positive, whereas there were 8144 SARS-CoV-2-positive tests in the control group between the second and fourth week after the second vaccine dose. The vaccine effectiveness against laboratory-confirmed SARS-CoV-2 infection was 55.3% (95% CI 41.3%–66.0%) in the first week after the second vaccine dose. The authors speculate that this could be due to the effect of the first vaccine dose. This increased to 87.1% (95% CI 81.0%–91.2%) in the second week, 91.2% (87.4%–93.8%) in the third week and 88.2% (95% CI 85.0%–90.7%) in the fourth week. However, the differences between the second, third and fourth weeks were not statistically significant. The adjusted vaccine effectiveness against positive infection at 2 to 4 weeks later was 91.5% (95% CI 88.2-93.9%).

According to the authors, they could not test the effectiveness of the vaccine against symptomatic disease as epidemiological investigation was done only for a small percentage of the vaccinated and unvaccinated cohorts (42% and 40%, respectively).

None of the vaccinated adolescents who tested positive for SARS-CoV-2 between 1 to 28 days after the second dose needed hospitalization as of August 26. Seven unvaccinated adolescents were hospitalized in the first week after the second dose of the vaccinated group, and 26 of the unvaccinated adolescents were hospitalized at 8 to 28 days. No deaths occurred among those testing positive in either group.

These findings suggest that the Pfizer vaccine is highly effective in providing short-term protection to the adolescents against the SARS-CoV-2 Delta variant.

Reference

1. Glatman-Freedman A, et al. Effectiveness of BNT162b2 vaccine in adolescents during outbreak of SARS-CoV-2 delta variant infection, Israel, 2021. Emerg Infect Dis. 2021 Sep 27;27(11). doi: 10.3201/eid2711.211886. Online ahead of print.