Economic evaluation of delivering hepatitis B vaccine to injection drug users

Abstract

Background: Injection drug users (IDUs) are at high risk of hepatitis B (HBV) infection, and hepatitis B vaccination coverage in IDUs is low. Recent studies demonstrate that syringe exchange programs are effective venues to reach and immunize IDUs. The purpose of this paper was to determine if targeting IDUs for HBV vaccination through syringe exchange programs is economically desirable for the healthcare system and to assess the relative effectiveness of several different vaccination strategies.

Methods: Active IDUs in Chicago IL and Hartford and Bridgeport CT (N=1964) were recruited and screened through local syringe exchange programs, randomized to a standard (0, 1, 6 months) or accelerated (0, 1, 2 months) vaccination schedule, and followed from May 2003 to March 2006. Analyses were conducted in 2007. The vaccination program's costs were balanced against future HBV-associated medical costs. Benefits in terms of prevented acute HBV infections and quality-adjusted life years were estimated based on a Markov model.

Results: HBV vaccination campaigns targeting IDUs through syringe exchange programs are cost-saving. The most cost-saving strategies include giving the first dose to everyone at screening, administering the vaccination under the accelerated schedule (0, 1, 2 months), and obtaining highly discounted vaccine from local health departments.

Conclusions: It is economically inappropriate to offer HBV screening in the absence of vaccination. Existing syringe exchange programs in the U.S. should include HBV vaccination.

Figures

Figure 1. Decision model for hepatitis B vaccination at syringe-exchange programs

This figure depicts four vaccination strategies and the no-vaccination strategy considered in the model. Depending on the strategy chosen, participants would receive the first dose either prior to knowing their serologic results or after learning they are susceptible according to their serologic results; the third dose would be administered on either a standard or accelerated schedule. Once participants initiate vaccination, they either return for their follow-up doses or fail to complete the vaccine series. The completion rates, successful immunization rates, and percentage of the susceptible were based on data obtained from the HVS study. Those who remain susceptible as a result of failing to begin the vaccine series, to complete the vaccine series, or to become successfully immunized were entered into a Markov model simulating the natural history of HBV infection. IDU, injection drug user

Figure 2. Markov model of disease states following HBV infection

This figure shows the dynamic flow of health states included in the model. People who develop acute infections could have three possible manifestations: asymptomatic, non-hospitalized symptomatic, and hospitalized symptomatic. These three manifestations were not explicitly stated in the Markov model, but different medical costs would be considered in the analysis. Some acute infections can progress to fulminant hepatitis. Although most acute infections are resolved in adults, a percentage—about 5%—develop chronic infection. The chronic infections may progress to compensated cirrhosis, to hepatocellular carcinoma (HCC), or to both. Compensated cirrhosis may progress to decompensated cirrhosis and subsequent HCC. Patients with fulminant or chronic hepatitis may subsequently undergo liver transplantation. The dotted line in this model describes the dynamic of permanent cessation of drug injection in the sensitivity analysis.