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: Clinical hepatitis developed in 1 . 4 % of HBIG and in 5 . 9 % of ISG recipients ( P = 0 . 016 ) , and seroconversion ( anti - HBs ) occurred in 5 . 6 % and 20 . 7 % of them respectively ( P less than 0 . 001 ) .
### Output Text:
Clinical hepatitis developed in 1 . 4 % of HBIG and in 5 . 9 % of ISG recipients ( P = 0 . 016 ) , and seroconversion ( anti - HBs ) occurred in 5 . 6 % and 20 . 7 % of them respectively ( P less than 0 . 001 ) . 