1. Chaoyang District Center for Disease Control and Prevention, Beijing, P.R. China
2. Liaoning Chengda biological Limited by Share Ltd, Shenyang, P.R. China
3. Guangdong Provincial Center for Disease Control and Prevention, Guangzhou, P.R. China
4. Wuhan City Center for Disease Control and Prevention, Wuhan, P.R. China
5. Guizhou Provincial Center for Disease Control and Prevention, Guiyang, P.R. China
6. Hunan Provincial Center for Disease Control and Prevention, Changsha, P.R. China
7. National Institutes for Food and Drug Control, Beijing, P.R. China