Childhood varicella vaccination: an evaluation of clinical effectiveness, safety and cost effectiveness in Ireland
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Date
2024
Authors
Ahern, Susan
Journal Title
Journal ISSN
Volume Title
Publisher
University College Cork
Published Version
Abstract
Background
Varicella (chickenpox) is a common, highly contagious, vaccine-preventable disease that mainly affects children. Although typically mild, serious complications requiring hospitalisation do occur. Varicella is also associated with significant productivity loss mainly due to absence from paid work for those caring for people who are sick with the disease. While 44 countries and regions globally recommend childhood varicella vaccination, recommendations differ between countries. Currently varicella vaccination is not offered as part of the routine childhood immunisation schedule in
Ireland.
Aim
The overall aim of this thesis was to analyse the clinical effectiveness and safety of childhood varicella vaccination and the cost effectiveness of universal childhood varicella vaccination in Ireland. In doing so, it sought to help inform a public health policy decision regarding the addition of varicella vaccination to the childhood immunisation schedule in Ireland.
Methods
This thesis applied the analytical tools of systematic review and economic evaluation across four inter-related studies. Two overviews of systematic reviews were conducted to synthesise the international evidence on the clinical effectiveness (study 1) and safety (study 2) of childhood varicella vaccination. To assess the most up-to-date international evidence on the approaches taken to the economic modelling of universal childhood varicella vaccination, and to inform the development of a de novo economic model for Ireland, a rapid review of economic modelling studies was undertaken (study 3). Lastly, a cost-utility analysis (CUA) was conducted to estimate the cost effectiveness of universal childhood varicella vaccination in Ireland (study 4).
Results
From a total of 20 systematic reviews, there was clear and consistent evidence that vaccination is very effective at reducing varicella. The evidence suggests that two-dose strategies are more effective than one-dose strategies in preventing varicella of any severity, but that both strategies have similarly high effectiveness in preventing moderate or severe varicella. From a total of 17 systematic reviews, the evidence suggests that mild local and systemic reactions are relatively common with varicella vaccination, and serious adverse reactions are rare. The rapid review of economic modelling studies identified a number of important structural features and input parameter data that were incorporated into the dynamic transmission model of varicella zoster virus developed for Ireland. Based on the CUA, it was found that from the perspective of the publicly funded healthcare system, a one-dose varicella vaccination strategy would be cost effective compared with no vaccination, with an incremental cost-effectiveness ratio (ICER) of €8,700 per quality-adjusted life year (QALY) gained. Relative to a one-dose strategy, a two-dose strategy would be less cost effective with an ICER of approximately €45,000 per QALY gained, with little difference in the cost effectiveness of a two-dose short interval and a two-dose long interval strategy. From a societal perspective, both one- and two dose vaccination strategies would be cost saving compared with no vaccination, with the two-dose short interval strategy dominant, being the least costly and most effective. The results of the CUA were robust to both sensitivity and scenario analyses.
Conclusion
The current evidence suggests that varicella vaccination is safe and highly effective in preventing varicella in children. While both one- and two-dose strategies are effective in preventing severe disease, a two-dose strategy is more effective in preventing varicella (cases and outbreaks). From a societal perspective, universal childhood varicella vaccination would be cost saving in Ireland. From the payer perspective, a one-dose strategy would be highly cost effective and sufficient to reduce severe morbidity from varicella. However, a two-dose strategy would be required to potentially achieve elimination of the disease. A policy decision to add the varicella vaccine to the childhood immunisation schedule in Ireland should consider the totality of the evidence presented in this thesis in the context of the stated aim of such a programme, that is, whether the aim is to reduce incidence of severe disease or eliminate varicella. Additionally, a decision to add another vaccine to the childhood immunisation schedule should consider relevant organisational, social and ethical issues.
Description
Keywords
Chickenpox , Immunisation , Vaccine effectiveness , Vaccine efficacy , Vaccine safety , Varicella , Cost-utility analysis , Vaccination , Overview of reviews , Economic evaluation , Cost effectiveness
Citation
Ahern, S. 2024. Childhood varicella vaccination: an evaluation of clinical effectiveness, safety and cost effectiveness in Ireland. PhD Thesis, University College Cork.