In the sentence extracted from biomedical literature, identify all the chemical entities. The required answer format is the same sentence with HTML <span> tags to mark up specific entities. 
### Entity Markup Guides:
Use <span class="chemical"> to denote a chemical.

### Input Text: Assessment was done on the following : prenatal screening for hepatitis B and rubella , administration of the hepatitis B vaccine birth dose to all infants , administration of hepatitis B immune globulin to infants who were born to hepatitis B surface antigen - positive mothers , rubella immunity , and administration of in - hospital postpartum rubella vaccine to rubella nonimmune women .
### Output Text:
Assessment was done on the following : prenatal screening for hepatitis B and rubella , administration of the hepatitis B vaccine birth dose to all infants , administration of hepatitis B immune globulin to infants who were born to <span class="chemical">hepatitis B surface antigen</span> - positive mothers , rubella immunity , and administration of in - hospital postpartum rubella vaccine to rubella nonimmune women . 