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Immunogenicity and Safety of a SARS-CoV-2 Inactivated Vaccine in Healthy Adults Aged 18-59 years: Report of the Randomized, Double-blind, and Placebo-controlled Phase 2 Clinical Trial

By Yan-Jun Zhang, Gang Zeng, Hong-Xing Pan, Chang-Gui Li, Biao Kan, Ya-Ling Hu, Hai-Yan Mao, Qian-Qian Xin, Kai Chu, Wei-Xiao Han, Zhen Chen, Rong Tang, Wei-Dong Yin, Xin Chen, Xue-Jie Gong, Chuan Qin, Yuan-Sheng Hu, Xiao-Yong Liu, Guo-Liang Cui, Cong-Bing Jiang, Heng-Ming Zhang, Jing-Xin Li, Min-Nan Yang, Xiao-Juan Lian, Yan Song, Jin-Xing Lu, Xiang-Xi Wang, Miao Xu, Qiang Gao, Fengcai Zhu

Posted 10 Aug 2020
medRxiv DOI: 10.1101/2020.07.31.20161216

BACKGROUND The top priority for the control of COVID-19 pandemic currently is the development of a vaccine. A phase 2 trial conducted to further evaluate the immunogenicity and safety of a SARS-CoV-2 inactivated vaccine (CoronaVac). METHODS We conducted a randomized, double-blind, placebo-controlled trial to evaluate the optimal dose, immunogenicity and safety of the CoronaVac. A total of 600 healthy adults aged 18-59 years were randomly assigned to receive 2 injections of the trial vaccine at a dose of 3 g/0.5 mL or 6 g /0.5mL, or placebo on Day 0,14 schedule or Day 0,28 schedule. For safety evaluation, solicited and unsolicited adverse events were collected after each vaccination within 7 days and 28 days, respectively. Blood samples were taken for antibody assay. RESULTS CoronaVac was well tolerated, and no dose-related safety concerns were observed. Most of the adverse reactions fell in the solicited category and were mild in severity. Pain at injection site was the most frequently reported symptoms. No Grade 3 adverse reaction or vaccine related SAEs were reported. CoronaVac showed good immunogenicity with the lower 3 g dose eliciting 92.4% seroconversion under Day 0,14 schedule and 97.4% under Day 0,28 schedule. 28 days after two-dose vaccination, the Nab levels of individual schedules range from 23.8 to 65.4 among different dosage and vaccination schedules. CONCLUSIONS Favorable safety and immunogenicity of CoronaVac was demonstrated on both schedules and both dosages, which support the conduction of phase 3 trial with optimum schedule/dosage per different scenarios.

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