This study demonstrated that integrating hepatitis B vaccination into existing syringe exchange programs would realize an economic benefit for the healthcare system. The most cost-saving and cost-effective vaccination strategy included giving the first dose to all screened participants prior to knowing their serological results and administering the vaccination under the accelerated schedule (0, 1, 2 months); this strategy saved almost a half-million dollars, realized a gain of 0.12 QALYs per person, and prevented 382 acute HBV infections for a cohort of 860 susceptible IDUs.
The cost saving of a hepatitis B vaccination program as demonstrated in this study was based on several factors. First, the target population had a comparatively high incidence rate of infection.13–15
Second, a high proportion (44%) of the target population remained susceptible to infection. Third, the medical costs of chronic HBV-associated illnesses are expensive, ranging from $1003 to $328,407 per person per year.36
Fourth, the sensitivity analysis indicated that at least 46% of the target population should have access to medical care when they get infected. Although health data were not collected in this study, 79.7% active IDUs in Connecticut are insured (unpublished data, 2002). However, it should be noted that having health insurance does not guarantee access to medical care. Fifth, the program is cost saving if less than 29% of IDUs permanently stop drug injecting annually. To our knowledge, there is no information in the literature concerning permanent injection-cessation rates. In fact, this rate would be difficult if not impossible to ascertain; it is imagined that a 29% cessation rate surpasses the actual rate. Economic benefit would be expected when implementing similar vaccination campaigns in other U.S. cities that satisfy the above conditions.
In addition, this study demonstrated that an investment in hepatitis B vaccination targeting IDUs through syringe exchange programs compared favorably to other HBV interventions targeting other high-risk groups in the U.S. The vaccination of hemodialysis patients was found to cost $261 per patient from the perspective of the healthcare sector.23
A recent study showed that routine hepatitis B vaccination costs $6.80 per adult client through HIV counseling and testing sites, and costs $7.40 per adult client through sexually transmitted disease clinics from the societal perspective.36
Only one previous hepatitis B vaccination study with the perspective of the healthcare sector also identified cost savings, and it demonstrated that providing hepatitis B vaccine for prison inmates would realize a saving of $45,000,000 for 381,646 inmates, approximately $118 per inmate involved.20
In contrast, the most cost-saving strategy in the current study could save $473,999 for 1964 IDUs, approximately $241 per IDU involved.
These estimates are conservative and likely underestimate the benefits of a hepatitis B vaccination program for IDUs. Only participants who were successfully protected by completing two or three doses were considered in this model. But those who completed only one dose were found to have successful immunization rates ranging from 5.4% to 20.4% in healthy adults in previous studies.56
Although the one-dose successful immunization rate would probably be lower among IDUs, one might reasonably expect some increase in protection by factoring that rate into the model. Furthermore, occult HBV infection was not taken into account in the current study’s model. A previous study showed that those with occult HBV infection might have higher probabilities of developing cirrhosis and hepatocellular carcinoma,57
which may incur greater medical costs for infected people compared to vaccinated people and increase the savings from vaccination. Moreover, because most HBV transmission is from individuals engaged in high-risk behaviors, the benefits of vaccination will be greater if secondary transmission to non-IDUs is considered in the model. In addition, the average age of IDUs in this study was 40. More savings would be realized by enrolling younger IDUs, because they may have a higher likelihood of developing protective antibody levels.58
The cohort effect of universal vaccination (implemented by the U.S. Public Health Service in the 1990s) should be considered in future models.
In conclusion, existing syringe exchange programs in the U.S. should include hepatitis B vaccination programs because they are effective in protecting IDUs against HBV infection and are economically beneficial to the healthcare system. This logic can be extended to any program or service that comes into repeated contact with high HBV-incidence populations such as IDUs.