China has set up a national work group on an immunization plan to improve vaccine supervision to ensure their safety, the head of the Chinese Center for Disease Control and Prevention said on Monday.

The work group, headed by a vice-minister of health, is analyzing all incidents concerning vaccine safety that have occurred over the past few years to find the  sources of problems, Gao Fu said at a news conference. He did not give the name of the minister.

"Vaccines made in China are some of the best in the world," Gao, also a member of China's top political advisory body, said, calling on the public not to lose faith in Chinese vaccines.

Gao made the comments following a series of incidents involving vaccine safety over the past few years.

In a major vaccine scandal last year, Changchun Changsheng Life Sciences Ltd, a vaccine producer in Changchun, Northeast China's Jilin province, was found to have violated the law, including faking production records and using expired material for vaccine production over the past four years.

Following the incident, top officials vowed harsh penalties and reforming the vaccine supervision system to eliminate loopholes.