evidence: Efficacy of the tetravalent protein COVID-19 vaccine, SCTV01E: a phase 3 double-blind, randomized, placebo-controlled trial [...] This phase 3 study was a randomized, double-blind, placebo-controlled evaluation of the efficacy and safety of SCTV01E, a tetravalent SARS-CoV-2 trimeric spike protein vaccine, in adults aged 18 years and above. Participants were recruited from 9 study sites located across three provinces in China, including Sichuan, Guizhou, and Hunan. The protocol of this study, the written informed consent form, and other information related to participants were approved by the clinical research ethics board of the Sichuan/Guizhou/Human Provincial Center for Disease Control and Prevention (China). This trial followed the Declaration of Helsinki, Good Clinical Practice (GCP) requirements, and related regulations issued by authorities.