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: Hepatitis B vaccine birth dose was administered to 76 . 2 % of all infants .
### Output Text:
Hepatitis B vaccine birth dose was administered to 76 . 2 % of all infants . 