Conflict of interest
Authors XL, SL, XGL and YG are employed by Sinovac Biotech Co., Ltd. Authors JS, YZ and GC are employed by Sinovac Life Sciences Co., Ltd.The remaining authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.The authors declare that this study received funding from Sinovac Life Sciences Co., Ltd.. The funder had the following involvement with the study: study design, data analysis, preparation of the manuscript.