1981
METHODS : We included data from people participating in the Vancouver Injection Drug Users Study who reported injecting illicit drugs at least once in the month before enrolment , lived in the greater Vancouver area , were HIV - negative at enrolment and completed at least 1 follow - up study visit .
 None
Please list all entity words in the text that fit the category.Output format is "type1: word1; type2: word2". 
Option: Disease, Chemical 
Text: {0} 
Answer:
 None