Effectiveness of ChAdOx1 nCoV-19 (Vaxzevria) primary series vaccine against SARS-CoV-2 beta and delta variants: a nationwide study.

ABSTRACT:

Background

This study assessed the real-world effectiveness of the ChAdOx1 nCoV-19 vaccine in adults against severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection, symptomatic infection, and severe coronavirus disease 2019 (COVID-19) during periods of Beta and Delta variant dominance in Qatar.

Methods

A national, matched, test-negative case-control study was conducted using 186,130 PCR-positive tests (cases) and 667,289 PCR-negative tests (controls) collected between January 1 and December 18, 2021. Subgroup analyses were performed to evaluate vaccine effectiveness across key strata.

Results

The median time between the first and second doses was 61 days (interquartile range, 56-64 days). Two-dose primary-series effectiveness was 66.0% (95% CI, 55.1-74

SUBMITTER: Chemaitelly H 

PROVIDER: S-EPMC12358068 | biostudies-literature | 2025 Aug

REPOSITORIES: biostudies-literature