Varicella is a common, highly infectious, vaccine-preventable, disease caused by the varicella zoster virus (VZV) which mainly affects children. Currently it is estimated that there are approximately 58,000 cases of varicella each year in Ireland. Primary infection with VZV results in varicella, after which the virus becomes latent in the body’s nervous system. The virus may reactivate after a period, sometimes several decades later, resulting in herpes zoster (shingles). Approximately one in three people will developing herpes zoster during their lifetime.
Varicella is typically a mild self-limiting disease but it can lead to long-term skin scarring and serious complications requiring hospitalisation. In very rare cases it can also lead to death in healthy as well as immunocompromised individuals. 

Although limited research has been published examining the total economic burden of VZV in Ireland, estimates suggest that the total burden, including both direct and indirect costs, is likely to be considerable. Indirect costs are driven by productivity loss associated with absence from paid work due to both illness and caring for those who are ill.

Currently there are four vaccines authorised for vaccination against varicella in Europe. Since the mid-1990s, the number of countries that have introduced funded universal childhood varicella vaccination programmes has grown and currently includes nine EU/EEA countries as well as Australia, Canada and New Zealand among others.
 

This research was carried out in accordance with HIQA’s guidelines for the conduct of HTAs. In summary:

• The terms of reference for the HTA were agreed between HIQA and the Department of Health. 
• An Expert Advisory Group (EAG) was convened comprising representation from the Department of Health, the National Immunisation Advisory Committee, the National Immunisation Office, the Health Protection Surveillance Centre, and the Irish College of General Practitioners. The EAG also included clinicians with specialist expertise in infectious diseases and public health, healthcare professionals from public health and general practice nursing, representatives from relevant patient advocacy groups and methodological experts.
• A protocol for the work to be undertaken was reviewed by the HIQA Expert Advisory Group and published on the HIQA website.
• The epidemiology of varicella in Ireland was described.
• The technologies, that is, the vaccines authorised for vaccination against varicella, were described. 
• Two overviews of systematic reviews were conducted to assess the safety and effectiveness of varicella vaccination strategies to protect people against varicella. 
• A rapid review was conducted 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.
• An economic model was developed to estimate the cost effectiveness and budget impact of the potential introduction of universal childhood varicella vaccination in Ireland. 
• Analyses of the organisational, social and ethical implications of the proposed introduction of a varicella vaccination programme were undertaken.
• The draft HTA report was reviewed by the EAG. The report was then made available for a six-week public consultation period, during which members of the general public and stakeholder organisations had the opportunity to provide feedback on the draft HTA report. Changes were made to the HTA report, as appropriate, following the public consultation.
• A final draft report was submitted to the Board of HIQA for approval. Following its approval, the completed assessment was submitted to the Minister for Health and the Department of Health as advice.
   

• Varicella (chickenpox) is a common, highly infectious, vaccine-preventable, disease, mainly affecting children. Although typically a mild disease, serious complications requiring hospitalisation occur in approximately one in 250 cases and it can also lead to long-term skin scarring. One in three who have had varicella will develop herpes zoster (shingles) during their lifetime. 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.
• The current evidence suggests that varicella vaccination is safe and effective in preventing varicella, including severe disease and its complications. 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 the perspective of the publicly funded healthcare system, a one-dose 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.
• From a societal perspective, which also considers productivity loss associated with absence from paid work due to both illness and caring for those who are ill, both one- and two-dose vaccination strategies would be cost saving compared with no vaccination.
• The incremental five year budget impact to the HSE of a varicella vaccination programme was estimated at between €13.1 million (one-dose) and €28.1 million (two-dose short interval).
• In the event of a decision to expand the childhood immunisation programme to include varicella, consideration should be given to:
  • whether the aim of the programme is to reduce severe disease (one-dose strategy) or eliminate varicella (two-dose strategy) 
  • the timing of doses in a two-dose schedule as this has implications for programme effectiveness and the settings (GP- and schools-based) in which the vaccines would be administered
  • an education programme for those involved in administering the vaccine as well as an information campaign to empower parents and to support informed decision-making.