[rsynnott]

> That is helpful, but even with a clean needle they will administer something possibly contaminated anyway

In general, the main drug-related vector for disease is needle sharing. Most pathogens wouldn't survive long in the actual heroin, and it's not clear how they'd get there in the first place.

[varispeed]

This is true, but many contaminants can still cause serious diseases and uneven distribution of active substances may lead to accidental overdose. Also unknown composition of the "drug" can cause unexpected interactions with other drugs people may be taking at the same time. There also seems to be no proof that drop in prevalence of those diseases caused by needle sharing actually is caused by this program and not by cultural change and education that maybe changing the method of administering the drug is "healthier" (e.g. consumers started to prefer smoking over injecting).