Vaccination could improve overall health in a high risk population.

Abstract

Although hepatitis B vaccine has been available since the early 1980s and is highly effective and long lasting, the rate of vaccination among injection drug users is extremely low despite the fact that the highest incidence of infection with hepatitis B is found in this group. The incidence of hepatitis B among cohorts of injection drug users who have previously tested negative ranges from 5% to 20% per year, and estimates of the proportion who have serological markers for vaccination (surface antibody to hepatitis B) range from 3% to 11%.1,2 From 50% to 90% of injection drug users in the United States have natural immunity to hepatitis B as a result of previous exposure to the virus,2 and this has probably had a greater net effect on limiting transmission than past vaccination campaigns; it cannot be seen as a public health achievement. The study by Seal and colleagues addresses this issue by describing the attitudes of injection drug users in San Francisco to immunization against hepatitis B and their experiences. Seal et al compared young injection drug users (that is, those younger than 30) with older users because most drug users become infected with hepatitis B virus during the first few years after beginning to inject. They also found that younger drug users were twice as likely as older users to report engaging in injecting and sexual behaviors that would increase the risk of becoming infected with hepatitis B virus. Thus, they recommend that efforts to prevent hepatitis B should focus on young injection drug users and those who have recently begun to inject. Approaches to vaccination should probably be determined locally, as illustrated by a cohort study of injection drug users in Seattle, where 713 of 1048 (68%) who had been injecting for 10 years or less tested negative for core antibody to hepatitis B (unpublished data). This study used a random number scheme to select participants from nine different settings including drug treatment programs to ensure that the sample was broadly representative of injection drug users in the community.3 Seal et al also reported that the majority of both young and older injection drug users had recently visited a healthcare provider but that despite these recent contacts, few had ever been screened for hepatitis B, offered a vaccination, or given any of the vaccinations that make up the series. They concluded that these visits to healthcare settings might provide opportunities for vaccinating young injection drug users. Their study describes the problem from the viewpoint of the injection drug user although interpretation of the findings is limited because there is no serologic data verifying the self-reported history of infection and vaccination. The small proportion of the study population that reported having been offered vaccination (25% of younger injection drug users and 13% of older users) is both notable and distressing. The failure of healthcare providers to offer vaccinations seems to arise from a belief that the patient may not return to complete the series and that patients may already be infected4. The greatest success in vaccination completion rates among injection drug users (70% to 85%) has been achieved in drug treatment settings where there is regular, sustained contact with the client5, 6, 7; however, even one or two doses of the vaccine may be sufficient to prevent severe hepatitis and chronic infection. In a recent survey of injection drug users in England, 18% of those who reported having previously been vaccinated tested positive for hepatitis B core antibody.8 No data exist to indicate that injection drug users who are already infected are being vaccinated. Only a minority of injection drug users are enrolled in drug treatment programs at any time, however sporadic contact with healthcare providers in other settings does occur. Community-level studies are needed to test a system in which each contact with an injection drug user is viewed as an opportunity for providing vaccination against hepatitis B. Agencies that might participate in this effort include health departments, prisons and jails, needle exchange programs, drug treatment agencies, physicians' offices, community clinics, hospital emergency departments, and community outreach programs. Wallet-sized vaccination records could be handed out to patients at high risk to allow them to keep track of vaccinations and screening tests. Developing a system to coordinate vaccinations may have other important benefits and improve the overall health of members of a high-risk population.