Abstract
BackgroundThe present study aims to evaluate the cost-effectiveness of the newly introduced varicella and herpes zoster (HZ) vaccination programmes in Italy. The appropriateness of the introduction of the varicella vaccine is highly debated because of concerns about the consequences on HZ epidemiology and the expected increase in the number of severe cases in case of suboptimal coverage levels.MethodsWe performed a cost-utility analysis based on a stochastic individual-based model that considers realistic demographic processes and two different underlying mechanisms of exogenous boosting (temporary and progressive immunity). Routine varicella vaccination is given with a two-dose schedule (15 months, 5–6 years). The HZ vaccine is offered to the elderly (65 years), either alone or in combination with an initial catch-up campaign (66–75 years). The main outcome measures are averted cases and deaths, costs per quality-adjusted life years gained, incremental cost-effectiveness ratios, and net monetary benefits associated with the different vaccination policies.ResultsDemographic processes have contributed to shaping varicella and HZ epidemiology over the years, decreasing varicella circulation and increasing the incidence of HZ. The recent introduction of varicella vaccination in Italy is expected to produce an enduring reduction in varicella incidence and, indirectly, a further increase of HZ incidence in the first decades, followed by a significant reduction in the long term. However, the concurrent introduction of routine HZ vaccination at 65 years of age is expected to mitigate this increase and, in the longer run, to reduce HZ burden to its minimum. From an economic perspective, all the considered policies are cost-effective, with the exception of varicella vaccination alone when considering a time horizon of 50 years. These results are robust to parameter uncertainties, to the two different hypotheses on the mechanism driving exogenous boosting, and to different demographic projection scenarios.ConclusionsThe recent introduction of a combined varicella and HZ vaccination programme in Italy will produce significant reductions in the burden of both diseases and is found to be a cost-effective policy. This programme will counterbalance the increasing trend of zoster incidence purely due to demographic processes.
Highlights
The present study aims to evaluate the cost-effectiveness of the newly introduced varicella and herpes zoster (HZ) vaccination programmes in Italy
Under the no vaccination scenario, both model structures predict a stable overall incidence of varicella over time (Fig. 1a), as well as an increase in HZ rate, which will stabilise only after some decades (Fig. 1d–f and Fig. 2). This growth can be ascribed to two factors, i.e. the population ageing that acts in both models, and the delayed effect, stronger for model progressive immunity (PI), of the decline in the fertility rate which occurred during the last century on the individual risk of HZ development
Model PI forecasts a peak in HZ incidence with respect to 2017 that amounts to 61.4% (95% PI 44.9–77.1%) and a stable incidence level in the long term that is 48.3% (95% PI 33.4–62.8%) higher than in 2017 (Fig. 2)
Summary
The present study aims to evaluate the cost-effectiveness of the newly introduced varicella and herpes zoster (HZ) vaccination programmes in Italy. Infection by VZV can result in two distinct diseases: varicella or chickenpox, which is a highly communicable and widespread childhood disease, and herpes zoster (HZ) or shingles, caused by the reactivation of VZV, which remains latent in the dorsal root ganglia after primary varicella infection. It is usually a mild disease with a relatively low percentage of complications, especially when occurring in immunocompetent children, varicella is highly contagious and may lead to more severe consequences and disabling symptoms in adults. Complications of HZ occur in up to 20% of the cases among those aged 50 or older, with post-herpetic neuralgia (PHN) being the most common, persistent, and intractable chronic sequela [1, 2]
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