Surveillance of adverse events following immunization in China: Past, present, and future.

Surveillance for adverse events following immunization (AEFI) is an important component of any national immunization program. In the People's Republic of China (China), a populous, middle-income country, development of an AEFI surveillance system began in 2005. In 2008, the AEFI surveillance system was implemented as a nationwide, online system and called the Chinese National AEFI Information System (CNAEFIS). Since then, CNAEFIS has provided useful, national-level data on vaccine safety. National AEFI surveillance guidelines were issued jointly by the Ministry of Health and the China Food and Drug Administration in 2010. This article reviews the development, status, and key aspects of the Chinese AEFI surveillance system, and describes challenges and future plans for vaccine safety assessment in China.