Effectiveness of BNT162b2 Vaccine against Delta Variant in Adolescents

Ben Y Reis, Noam Barda, Michael Leshchinsky, Eldad Kepten, Miguel A Hernán, Marc Lipsitch, Noa Dagan, Ran D Balicer

Research output: Contribution to journalArticlepeer-review

Abstract

The B.1.617.2 (delta) variant of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has emerged as the dominant strain circulating in many regions worldwide. The BNT162b2 mRNA vaccine against coronavirus disease 2019 (Covid-19) was found to be effective in preventing infection with the delta variant in a recent observational study,1 but other reports have suggested reduced vaccine effectiveness against this variant.2,3 On May 10, 2021, the U.S. Food and Drug Administration approved the emergency use of BNT162b2 in adolescents 12 years of age or older on the basis of a clinical trial that had been conducted before the delta variant had become prevalent in the United States.4 Additional evidence was needed regarding the effectiveness of the BNT162b2 vaccine among adolescents, particularly against the delta variant.

We sought to estimate the vaccine effectiveness of BNT162b2 against the delta variant among vaccinated adolescents for whom an unvaccinated match was found. We used data from Clalit Health Services, the largest health care organization in Israel, to conduct an observational cohort study involving adolescents between the ages of 12 and 18 years who had no prior SARS-CoV-2 infection noted in their electronic medical record and who had been vaccinated between June 8 and September 14, 2021. According to the sequencing of samples obtained from infected persons that was performed by the Israeli Ministry of Health during this period, the delta variant was responsible for more than 95% of new infections in the general population in Israel.

We used the same methods that were used in our previous studies of vaccine effectiveness, which were conducted in the same health care organization using the same database.5 (See the Methods section in the Supplementary Appendix, available with the full text of this letter at NEJM.org.) Vaccine effectiveness was defined as 1 minus the risk ratio, which was estimated over several follow-up periods for documented SARS-CoV-2 infection and symptomatic Covid-19. More severe outcomes related to Covid-19 are rare in this age group.
Original languageEnglish
JournalNew England Journal of Medicine
DOIs
StatePublished - 2021

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