21982
Skin and serum samples were collected over 96h , IFN alpha levels were determined by an antiviral assay , and half - life ( t1 / 2 ) and elimination ( k ) rates were calculated .
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Please list all entity words in the text that fit the category.Output format is "type1: word1; type2: word2". 
Option: Chemical 
Text: {0} 
Answer:
 None