A baseline study in Injection Drug Users (IDUs) in Greater Stockholm was conducted at the request of the local health authorities. Active IDUs were those that admitted to have injected at least once in the last 12 months; the vast majority tested had injected several times in the past week. We interviewed and tested 714 such IDUs during a two year period, mostly during the summer season. An important and cumbersome component of our study was to report back the results to the person tested and explain the consequences of the results or initiate vaccination where possible.

Most persons tested were contacted on site, i.e. where injection abuse was known to occur, but also at institutions where drug addicts were regularly seen. A useful tool in such a study is the mobile phone as it turned out that almost all IDUs were equipped with one through which they could eventually be reached for follow-up visits. Thus, mobile phones used by mobile teams were key components in this study.

We found that 7 % of those tested were infected with HIV, a prevalence which is about 100 times higher than that in the general adult Swedish population. Eleven of the patients concerned were not known cases and they were therefore referred to an HIV clinic. More than 80 % were HCV positive and those not known to be positive before were referred to a liver infection unit. About 50 % were HBV antibody positive, mostly through natural infection. Although HBV vaccination of non-immune IDUs is mandatory in Sweden, more than 300 of them had not been vaccinated although they had passed through numerous medico-social institutions where such vaccinations could have been performed.   All of those amenable to vaccination agreed to have it done and thus were immunized as part of the study. Through our extensive out-reach study we conclude that the number of active IDUs in Greater Stockholm was far smaller than anticipated. This information is essential when new harm reduction initiatives are planned for IDUs in Stockholm.