Numerical quantification (in times per week) of the injecting and sharing events.

Panel A. Numerical quantification (in times per week) of the injecting (both cohorts), and sharing events from categorical answers of the prospective cohort, provided by subjects during the HITS-p interviews to the questions “Since the last interview, how often did you inject drugs?” and “Since the last interview, how often did you use injecting equipment after someone else had used it?”. Panel B. Numerical quantification (as a percentage of the number of IDU events) of the sharing events in the retrospective cohort, based on the question “Since last imprisonment, how often did you use equipment after someone else had used it?”.