ChAdOx1 nCoV-19 Vaccine Efficacy against the B.1.351 Variant
Shabir A. Madhi, Alane Izu, Andrew J. Pollard
Abstract
To the Editor: Madhi et al. (May 20 issue) 1 report on the efficacy of vaccination with the recombinant adenoviral vector encoding the spike protein antigen of SARS-CoV-2 (ChAdOx1 nCoV-19) against the SARS-CoV-2 B.1.351 (or beta) variant lineage. They commented that in the ENSEMBLE study evaluating the efficacy of the Ad26.COV2.S vaccine, only patients with infection that was confirmed by polymerase-chain-reaction assay who had at least three signs or symptoms of Covid-19 were approved for end-point adjudication. The authors incorrectly concluded that the vaccine efficacy analyses excluded the majority of mild Covid-19 cases. However, all patients with mild or moderate cases of Covid-19 who had one or two symptoms did not require adjudication for confirmation as a case and were included in primary or secondary efficacy analyses, as detailed in the protocol. The Clinical Severity Adjudication Committee was established to independently assess, in a blinded manner, potential severe or critical cases of Covid-19, adjudicating all cases meeting the criteria for severe-critical disease and all cases meeting the criteria for moderate disease with at least three signs or symptoms to determine whether the case was severe-critical in their judgment. 2 This focused process yielded blinded, independent confirmation of severecritical cases by clinical infectious disease experts and pulmonologists, ensuring the robustness and clinical relevance of this important end point.