4550
We performed a single - blind , placebo - controlled study to assess its effectiveness and safety in Chinese hepatitis B surface antigen ( HBsAg ) carriers .
 Chemical: hepatitis B surface antigen; Chemical: HBsAg
Please list all entity words in the text that fit the category.Output format is "type1: word1; type2: word2". 
Option: Disease, Chemical 
Text: {0} 
Answer:
 Chemical: hepatitis B surface antigen; Chemical: HBsAg