Jiangsu Provincial Center for Disease Control and Prevention, Nanjing, Jiangsu 210009, P. R. China;
National Institutes for Food and Drug Control, Beijing 100050, P. R. China;
Jiangsu Provincial Center for Disease Control and Prevention, Nanjing, Jiangsu 210009, P. R. China;
Jiangsu Provincial Center for Disease Control and Prevention, Nanjing, Jiangsu 210009, P. R. China;
GlaxoSmithKline Biologicals, B-1300 Wavre, Belgium;
GlaxoSmithKline, Shanghai 200001,P. R. China;
GlaxoSmithKline Biologicals, B-1300 Wavre, Belgium;