[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).