Varicella vaccination in Italy : an economic evaluation of different scenarios.

Abstract

To determine the economic impact (cost-benefit analysis) of childhood varicella vaccination, with the Oka/Merck varicella zoster virus vaccine live (Varivax) in Italy. This analysis is based on an epidemiological model of varicella zoster virus (VZV) dynamics adapted to the Italian situation. Cost data (Euro, 2002 values) were collected through a literature review. Several vaccination scenarios were analysed: (i) routine vaccination programme for children aged 1-2 years with different levels of vaccination coverage (90%, 70% and 45%) without any catch-up programme; (ii) routine vaccination programme for children aged 1-2 years with different levels of vaccination coverage (90%, 70% and 45%) completed by a catch-up programme for 6-year-old children over the first 5 years of vaccine marketing; and (iii) routine vaccination programme for children aged 1-2 years with different levels of vaccination coverage (90%, 70% and 45%) completed by a catch-up programme during the first year of vaccine marketing for children aged 2-11 years. A societal perspective, including both direct and indirect costs, and a health-system perspective, limited to costs supported by Italian Health Authorities, were considered. A routine vaccination programme has a clearly positive impact on chickenpox morbidity. Respectively, 68% and 57% of chickenpox-related hospitalisations and deaths could be prevented with a 90% coverage rate. With vaccination costs being more than offset by a reduction in chickenpox treatment costs in the base case, such a programme could also induce savings from both a societal and a health-system perspective (40% and 12% savings, respectively for a 90% coverage rate). A lower coverage rate reduces cost savings, but there is still a 9% decrease in overall societal costs for a 45% coverage rate. Although the reduction in total societal costs was robust to the sensitivity analyses performed, a slight uncertainty remains regarding cost reduction from a health-system perspective. However, in this latter perspective, even in the worst-case scenario of the sensitivity analysis, routine vaccination programmes may be cost effective, the worst-case scenario for cost parameters leading to cost per life-year gained of Euro2853. Catch-up programmes combined with routine vaccination should lead to further cost reductions from a societal perspective: 15% for a massive catch-up during the first year of vaccine marketing compared with toddlers' vaccination alone, and 11% for a catch-up focused on 6-year-old children for a period of 5 years. However, the impact of catch-up programmes on the costs from an Italian health-system perspective remains close to zero (+/-1%). This model suggests, with its underlying assumptions and data, that routine ZVZ vaccination may be cost saving from both a societal and a health system perspective in the base case. In the worst-case scenario of the sensitivity analysis, vaccination remains cost effective.