Efficacy of the mRNABNT162b2 COVID-19 vaccine up to 6 months in a large US integrated health care system: a backward-looking cohort study

Publication date: October 4, 2021 DOI: https : //doi.org/10.1016/S0140-6736(21)02183-8

Commentary

Vaccine efficacy studies to date have not distinguished between the effects of the delta (B.1.617.2) variant and the possibility of reduced immunity when reduced efficacy against SARS-CoV-2 infection is observed.

The study aimed to evaluate the overall and variant-specific efficacy of BNT162b2 (tozinameran, Pfizer-BioNTech) against SARS-CoV-2 infection and COVID-19-related hospitalizations by time since vaccination among members of a large US health care system.

The study included 3,436,957 of the 4,920,549 patients assessed for eligibility between December 14, 2020 and August 8, 2021.

In fully vaccinated individuals, efficacy against SARS-CoV-2 infection was 73%, and efficacy against COVID-19-related hospitalizations was 90%.

Efficacy against infections was shown to decline from 88% in the first month after full vaccination to 47% five months later.

Among the sequenced infections, vaccine efficacy against infections of the delta variant was high in the first month after full vaccination (93% [95% CI 85-97]), but declined to 53% [39-65] after 4 months.

Efficacy against other (non-delta) variants in the first month after full vaccination was also high at 97%, but decreased to 67% (45-80) at 4-5 months.

Vaccine efficacy against hospitalization for infections caused by delta variants of all ages was high overall up to 6 months (93% [95% CI 84-96]).