OBJECTIVES: Chickenpox is generally a mild, self-limiting childhood disease; however, the large number of children infected each year can lead to considerable health and economic burden. Countries worldwide continue to debate the benefits and costs of a chickenpox vaccination program. In this study we assessed the cost-effectiveness of a universal chickenpox vaccine in Alberta, Canada using an agent-based model.

METHODS: We used an agent-based model to conduct a cost-utility analysis measuring the quality adjusted life years and costs over 75 years of three different chickenpox vaccine scenarios: [1] no vaccination, [2] long dosing interval (MMRV at 12 months and 4-6 years) and [3] short dosing interval (MMRV at 12 and 18 months). The model was calibrated and parameterized using real-world data. This study is the first to use an agent-based model to test the cost-effectiveness of the chickenpox vaccine, and therefore offers unique opportunities to better represent the spread of infection through network-based interaction, and to express endogenous dynamics (e.g. increasing shingles rates following chickenpox vaccination).

RESULTS: We ascertained that vaccination was cost-saving from the societal perspective and that it was cost-effective (<20,000$ per QALY) from the healthcare perspective. Chickenpox vaccine was never cost-effective when assuming a substantial increase of shingles following vaccination (i.e., 10 years post-vaccination an increase of 70 cases per 100,000 person-years). However, our model found that shingles rates may not increase that dramatically following vaccination, and these findings were supported in Canadian epidemiological studies. We found no significant difference in the cost-effectiveness of the shorter and longer dosing intervals.

CONCLUSIONS: The universal chickenpox vaccination program in Alberta is likely cost-effective now and into the future. By using agent-based modelling we could [1] better predict the impact of chickenpox vaccination on shingles rates, [2] more precisely estimate vaccine effectiveness, and [3] improve the testing of different vaccine dosing intervals.