1. Institute for Vaccine Clinical Research, Hebei Province Center for Disease Control and Prevention, Shijiazhuang, People’s Republic of China
2. National Engineering Technology Research Center for Combined Vaccines, Wuhan Institute of Biological Products Co., Ltd, Wuhan, People’s Republic of China
3. National Institutes for Food and Drug Control, Beijing, China
4. Zhengding County Center for Disease Control and Prevention, Zhengding, People’s Republic of China