Hepatitis B Vaccine: A Pharmacoeconomic Evaluation of its Use in the Prevention of Hepatitis B Virus Infection

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SummarySynopsisWorldwide, hepatitis B virus (HBV) infection is a major cause of acute and chronic hepatitis, cirrhosis and hepatocellular cancer. Infants and children are at the greatest risk of becoming chronically infected with HBV, and therefore at the greatest risk of developing long term sequelae. Immunisation against HBV represents an important means of controlling the disease. Hepatitis B vaccines are effective in preventing HBV infection and are well tolerated. In addition, they are suitable for integration into mass neonatal vaccination programmes.While there are considerable economic data concerning hepatitis B vaccination, differing methodologies and end-points present a challenge in reviewing these studies for consistent findings. Immunisation strategies should be implemented in accordance with local area disease incidence and patterns of HBV transmission, and will be influenced by regional budgetary constraints.In conclusion, universal neonatal vaccination is both cost effective and appropriate for control of HBV infection in regions of medium or high endemicity. In low endemicity areas, selective vaccination of high-risk groups is cost effective, but its impact on the incidence of HBV infection will depend on the ability to reach these groups. Expanded vaccination strategies may be appropriate where local conditions prohibit efficient access to high-risk groups.Epidemiological Considerations and Immunisation StrategiesThere is wide global variation in patterns of hepatitis B virus (HBV) prevalence, and strategies for use of hepatitis B vaccine must take into account these geographical differences. Prevention of HBV carriage is essential in achieving control of HBV transmission and infection.Universal vaccination of neonates is recommended for areas of high or intermediate endemicity as HBV infection in these regions is widespread, and occurs primarily at birth and during early childhood. This uniformity of infection risk has simplified the design of immunisation strategies. However, in areas of low endemicity, epidemiological patterns of HBV transmission are more complex, with infection occurring mainly in various high-risk groups. For this reason, vaccination in low endemicity areas has predominantly been selective, targeting high-risk groups. However, an adequate level of compliance in at-risk individuals may not be achievable in some countries; thus, expanded vaccination programmes may be more effective in controlling the disease. Recent preliminary data indicating a declining rate of HBV infection in many countries of low endemicity, apparently the result of lifestyle changes, further complicates assessment of the merit of expanded immunisation practices in areas of low disease incidence.Universal infant immunisation is an attractive option since the infrastructure for widespread vaccination already exists. However, it may take several decades for the benefits of this strategy to become evident. Mass immunisation of adolescents would produce more immediate financial savings but may be more difficult to implement.Prophylactic Efficacy and TolerabilityPlasma-derived and recombinant yeast-derived hepatitis B vaccines are available. Both vaccines have similar efficacy and tolerability profiles, and preliminary evidence indicates that they are also immunogenic when administered concurrently with other vaccines.Hepatitis B vaccination produces a protective antibody response in greater than 95% of healthy individuals aged less than 40 years following administration of 3 intramuscular doses. Initial data suggests that hepatitis B vaccines given without hepatitis B immune globulin are effective in preventing HBV infection in neonates born to mothers who are chronic HBV carriers. The duration of protection afforded by the vaccine has not been fully defined, although preliminary evidence suggests protection against developing carrier status lasts up to 10 years. Currently, there are no formal recommendations for revaccination.Hepatitis B vaccines are well tolerated. Both vaccine types possess similar adverse events profiles, with soreness at the injection site being the most frequently reported adverse event. A direct association between the plasma-derived vaccine and Guillain-Barré syndrome has not been established and to date, yeast-hypersensitivity reactions have not been reported after administration of the recombinant yeast-derived vaccine.Pharmacoeconomic ConsiderationsComprehensive economic analysis of immunisation programmes is difficult. Lack of a standard methodology and uniform end-points complicates interpretation of results and comparison of studies. In addition, economic evaluations are heavily influenced by local demographics, epidemiology and political priorities.Most cost-benefit analyses were performed from the societal perspective, while cost-effectiveness studies adopted less expansive viewpoints, most commonly that of the health authority. Sensitivity analyses have demonstrated that economic end-points are primarily sensitive to vaccine acquisition costs, prevalence of HBV markers and discount rate. Most analyses discounted costs and benefits, using rates of 3 to 8%. Evaluations of neonatal vaccination discounted heavily because of the long term sequelae of HBV infection.The decision whether to screen before vaccination is primarily a pharmacoeconomic issue, based on the expected prevalence of serological HBV markers and the annual rate of infection in the population concerned. Prevaccination screening will usually be cost-effective compared with vaccinating without screening in high-risk groups such as male homosexuals and hospital personnel. In groups at high risk it appears more cost effective to screen for antibodies to HBV core antigen than antibodies to HBV surface antigen.Both cost-benefit and cost-effectiveness evaluations of hepatitis B vaccines have consistently demonstrated positive economic returns for selective vaccination of high-risk groups, including neonates born to maternal carriers. Depending on local conditions, selective vaccination programmes that are diligently applied can be effective in controlling HBV infection.Increasing evidence that the vaccine affords long term immunity, and the importance of vaccinating individuals before they engage in high-risk behaviour, are factors favouring more expansive immunisation policies. However, while universal strategies are appropriate for countries of high or intermediate endemicity, their economic attractiveness in countries of low endemicity requires further evaluation.Economic evaluations of broader immunisation programmes are limited and comprise only cost-effectiveness studies. In a seminal study, performed more than a decade ago, vaccination of the general US population was not found to be cost effective compared to no vaccination. However, 2 more recent studies have demonstrated expanded immunisation programmes, including universal neonatal vaccination, to be more cost effective than previously thought. This appears attributable to increases in costs of illness, the incidence of disease and opportunities to negotiate lower vaccine acquisition costs.The decision whether to implement a universal immunisation programme in a country of low endemicity will be a difficult one, especially in the current climate of fiscal constraint. Furthermore, there is growing evidence that lifestyle changes have been instrumental in reducing the incidence of HBV infection in many countries of low endemicity. An important factor will be educating the public about the serious consequences of HBV infection, to encourage support for the use of public funds for a HBV prevention programme.

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