"Though unheard-of in the United States, supervised injection sites have existed in Europe for years — one of the first was in Switzerland, 30 years ago — and in Vancouver, British Columbia, the only city in North America where the practice is allowed. They have been linked to a reduction in harm from heroin abuse: In Vancouver, fatal overdoses dropped 35 percent in the community surrounding its main injection site in the two years after it opened in 2003 and fell 9 percent citywide."