Study Examines Effectiveness of BNT162b2 Vaccine Against Delta Variant In Adolescents

The Clalit Research Institute, in collaboration with researchers at Harvard University, analyzed one of the largest integrated databases of health records in the world to examine the effectiveness of the Pfizer / BioNTech BNT162B2 vaccine against the Delta variant of SARS-CoV-2 in adolescents. The study provides the largest peer-reviewed assessment of the effectiveness of a COVID-19 vaccine in adolescents in a national mass vaccination setting, and the first such study where the Delta variant was dominant. The study was conducted in Israel, one of the world’s first leaders in COVID-19 vaccination rates.

The results of this study validate and complement previously reported results from a Pfizer / BioNTech Phase III randomized clinical trial, which focused on symptomatic infections in the face of non-Delta variants, and which, with 1,983 adolescents vaccinated aged 12 and 15, could not accurately assess the efficacy of the vaccine. The large size of the present study allows a more precise assessment of the efficacy of the vaccine over different time periods.

The study ran from June 8, 2021 to September 14, 2021. It coincided with the fourth wave of coronavirus infection and disease in Israel, in which the Delta variant (B.1.617.2) was the dominant strain in the country for new infections.

The researchers looked at data from 94,354 vaccinated adolescents aged 12 to 18. These adolescents were carefully matched with 94,354 unvaccinated adolescents based on a broad set of demographic, geographic and health attributes associated with risk of infection, risk of serious illness, health status and health. search behavior. Individuals were dynamically assigned to each group based on their changing immunization status (13,423 individuals moved from the unvaccinated to the vaccinated cohort during the study). Multiple sensitivity analyzes were performed to ensure that the estimated vaccine efficacy was robust to potential biases.

The results show that in fully vaccinated adolescents (7 to 21 days after the second dose), the risk of symptomatic COVID-19 decreased by 93% compared to unvaccinated, while the risk of documented infection decreased by 90 %. In the period immediately before the second dose (days 14-20 after the first dose), vaccine efficacy was lower, but still substantial – the risk of symptomatic COVID-19 decreased by 57% in those vaccinated, and the risk of documented infection of 59%. The data were insufficient to provide an estimate of the reduction in the incidence of serious illness, hospitalizations and mortality, as these findings are rare in adolescents.

The research was conducted by Dr Noam Barda, Dr Noa Dagan, Michael Leshchinsky, Dr Eldad Kepten and Professor Ran Balicer of the Clalit Research Institute, as well as Professor Miguel Hernán and Professor Marc Lipsitch of the Harvard TH Chan School of Public Health, and Professor Ben Reis of Boston Children’s Hospital and Harvard Medical School.

“The large nationwide rollout of the Israeli COVID-19 vaccination campaign among adolescents at the very beginning of the wave of delta variants, provided the Clalit Research Institute with a unique opportunity to assess, thanks to its datasets Comprehensive digital data, the efficacy of the adolescent delta vaccine in a real-world setting, ”said Professor Ran Balicer, lead author of the study, director of the Clalit Research Institute and director of innovation for Clalit. “These results convincingly show that a week after the second dose, this vaccine is very effective in adolescents against symptomatic COVID-19 and against all documented infections. This data should facilitate informed individual decision making about risks and benefits and, in our opinion, make a strong case for the option of getting vaccinated, especially in countries where the virus is currently prevalent ” added Prof Balicer, who is also chairman of Israel’s national team of advisory experts on the response to COVID-19.

Professor Ben Reis, director of the Predictive Medicine Group at the Boston Children’s Hospital Computational Health Informatics Program and Harvard Medical School, said: “To date, one of the main drivers of vaccine reluctance has been the lack of vaccine information. This careful epidemiological study provides reliable information on the effectiveness of the vaccine, which we hope will be of use to those who have not yet decided to be vaccinated.

This research is a prime example of the complementarity of randomized trials and observational healthcare databases. The adolescent-focused Pfizer / BioNTech vaccine trial provided compelling evidence for its effectiveness in preventing symptomatic infections, but estimates for severe disease and specific age groups were too imprecise. This analysis of Clalit’s high-quality database emulates the original trial design, uses its results as a baseline, and expands them to confirm vaccine efficacy in adolescents. This combination of evidence from randomized trials and observational studies is a model for effective medical research, something that is especially important in the days of COVID. “

Teacher. Miguel Hernán, Director, CAUSALab and Professor, Harvard TH Chan School of Public Health

Professor Marc Lipsitch, director of the Center for Communicable Disease Dynamics and professor at Harvard TH Chan School of Public Health, said: “In all studies of vaccine effectiveness, a major challenge is to ensure that those that we compare to identify the vaccine effect are similar in other characteristics that can predict whether they are infected or sick. This is particularly difficult in the context of a rapidly growing age-targeted vaccination campaign. in a way that gives great confidence in the inferences that emerge from the study. “


Journal reference:

Reis, BY, et al. (2021) Efficacy of BNT162b2 vaccine against Delta variant in adolescents. New England Journal of Medicine.

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Sara H. Byrd

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