EDITOR—In their study of bloodborne viral infection in Irish prisons, Allwright et al found that infection with hepatitis C was associated with continued drug use by injecting in that setting.1 A study by Stark in Germany has also confirmed this finding.2 The authors of both studies have highlighted the discrepancy between the existence of well developed harm reduction programmes in the community, which include needle exchange and methadone maintenance, and the absence of such services in prisons.

I support the principle that imprisonment should not deprive an individual of access to services that are proved to reduce harm. Examination of the currently available research evidence, however, indicates that provision of needle exchange could possibly cause an increase in transmission of bloodborne viral infection in prisons. The findings reported by Allwright and Stark actually support this concern as they indicate that many injectors stop injecting while imprisoned.

In the Irish prison study, 51% of injecting drug users had not injected in the month before interview.1 In the German study, 53% of injectors had never injected while in prison.2 An Australian study, examining incidence of hepatitis C among prisoners, found that longer stay in prison (with no access to needle exchange) protected injectors against infection.3 One plausible interpretation of this research evidence is the following: injectors who inject in prison tend to do so unsafely, but as so many injectors cease injecting during their sentence, the incidence of infection (and other adverse events such as accidental overdose) drops among the total population of imprisoned injectors.

There has been insufficient examination of the reasons why so many injectors cease or curtail injecting while in prison. There are many possible explanations for …