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Antiviral therapy is obviously needed to control those infections that are not amenable to prophylaxis by vaccination , but is also highly desirable for those infections where vaccination has not been implemented or did not fulfill its premises for complete protection .
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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:
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