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: These infants are treated with two injections of hepatitis B immune globulin ( HBIG ) and at least three injections of plasma derived hepatitis B vaccine .
### Output Text:
These infants are treated with two injections of hepatitis B immune globulin ( HBIG ) and at least three injections of plasma derived <span class="chemical">hepatitis B vaccine</span> . 