The safety and immunogenicity of an inactivated SARS-CoV-2 vaccine in Chinese adults aged 18–59 years: A phase I randomized, double-blinded, controlled trial

Pu, Jing; Yu, Qin; Yin, Zhifang; Zhang, Ying; Li, Xueqi; Yin, Qiongzhou; Chen, Hongbo; Long, Runxiang; Zhao, Zhimei; Mou, Tangwei; Zhao, Heng; Feng, Shiyin; Xie, Zhongping; Wang, Lichun; He, Zhanlong; Liao, Yun; Fan, Shengtao; Jiang, Ruiju; Wang, Jianfeng; Zhang, Lingli; Li, Jing; Zheng, Huiwen; Cui, Pingfang; Jiang, Guorun; Guo, Lei; Xu, Mingjue; Yang, Huijuan; Lu, Shan; Wang, Xuanyi; Gao, Yang; Xu, Xingli; Cai, Linrui; Zhou, Jian; Yu, Li; Chen, Zhuo; Hong, Chao; Du, Dan; Zhao, Hongling; Li, Yan; Ma, Kaili; Ma, Yunfei; Liu, Donglan; Yao, Shibao; Li, Changgui; Che, Yanchun; Liu, Longding; Li, Qihan

BACKGROUND: This study examined the safety and immunogenicity of an inactivated SARS-CoV-2 vaccine. METHOD: In a phase I randomized, double-blinded, placebo-controlled trial involving 192 healthy adults 18–59 years old, two injections of three doses (50 EU, 100 EU, 150 EU) of an inactivated SARS-CoV-2 vaccine or placebo were administered intramuscularly at a 2- or 4-week interval. The safety and immunogenicity of the vaccine were evaluated. RESULTS: Vaccination was completed in 191 subjects. Forty-four adverse reactions occurred within 28 days, most commonly mild pain and redness at the injection site or slight fatigue. At days 14 and 28, the seroconversion rates were 87.5% and 79.2% (50 EU), 100% and 95.8% (100 EU), and 95.8% and 87.5% (150 EU), respectively, with geometric mean titers (GMTs) of 18.1 and 10.6, 54.5 and 15.4, and 37.1 and 18.5, respectively, for the schedules with 2-week and 4-week intervals. Seroconversion was associated with synchronous upregulation of antibodies against the S protein, N protein and virion and a cytotoxic T lymphocyte (CTL) response. No cytokines and immune cells related to immunopathology were observed. Transcriptome analysis revealed the genetic diversity of immune responses induced by the vaccine. INTERPRETATION: In a population aged 18–59 years in this trial, this inactivated SARS-CoV-2 vaccine was safe and immunogenic. Trial registration: CTR20200943 and NCT04412538.