Article 2 Preventive health examination refers to the health examination before, during and during the post of employees engaged in the production and operation of food and drinking water, those directly engaged in the production of cosmetics, those who directly serve customers in public places, hazardous workers, radiation workers and school students in accordance with relevant national health laws and regulations.
This is the origin of health certificate. Excerpt from: Administrative Measures for Preventive Health Examination
(decree number. 411released by the Ministry of Health on June 2, 995)