R otavirus (RV) is a major cause of acute gastroenteritis (AGE) in children under the age of fi ve and is a signifi cant cause of early childhood mortality in developing countries and morbidity in developed countries.1 Estimates for Australia from the mid 1990s put the direct national healthcare burden of RV at 10,000 hospital admissions 2 and 50,000 primary care visits 3 annually. These estimates were compiled to provide primary data for a cost-effectiveness analysis of RV vaccination in Australia. 3The previous cost-effectiveness analysis was framed around the vaccine Rotashield, which was licensed in the United States in 1998 but was voluntarily withdrawn from the market by its manufacturer a short time later after surveillance revealed an increased incidence of intussusception in infants who had been immunised. 4 Since then, several new RV vaccines have been under development and two were approved for use in Australia in 2006.5 In this context, this paper presents updated epidemiological data on numbers and costs of hospitalisations of young children in Australia for AGE and on the fraction of these hospitalisations that are attributable to RV (the 'RV fraction'). Estimates of numbers and costs of emergency department (ED) visits and numbers of general practitioner (GP) visits in Australia for RV-AGE are also included. A new method for estimating the RV fraction on the basis of the seasonal pattern of incidence is used.

Currently the Australian government funds universal influenza vaccine for all those aged > or =65 years under the National Immunisation Program (NIP). Annual vaccination rates in those aged 50-64 years are significantly lower than vaccination rates in those aged > or =65 years, and currently less than half those at high-risk of influenza-related complications aged 50-64 years are immunised. This study used a decision tree model to examine the cost-effectiveness of lowering the age threshold for the influenza NIP in Australia to include those aged 50-64 years. From a healthcare payer perspective, a new influenza vaccination policy would cost $8908/QALY gained. From a societal perspective, a new influenza vaccination policy would cost $8338/QALY gained. From a governmental perspective, a new influenza vaccination policy would cost $22,408/QALY gained. The most influential parameters in deterministic sensitivity analysis included: probability of death due to influenza, vaccine efficacy against mortality, vaccine uptake, vaccine cost, and vaccine administration cost. Influenza vaccination for people aged 50-64 years appears highly cost-effective, and should be a strong candidate for funding under the NIP.

Several recent studies have assessed the benefits of extending influenza vaccination programmes, which are currently targeted primarily at those aged over 65 years, to those aged 50-64 years. We identified and reviewed all cost-effectiveness studies of influenza vaccination in those aged 50-64 years published before July 2008. While the studies suggest that vaccination in this age-group is likely to be cost effective, these results were dependent on several key assumptions. The estimates of serious outcomes due to influenza and the estimates of vaccine effectiveness (VE) against these outcomes were found to have the most influence on cost effectiveness. However, due to factors including mismatches between the measure of VE and the outcome under consideration, as well as various other data limitations, there is significant uncertainty around these key assumptions that was not well explored. There was a failure in some studies to report fundamental inputs such as discount rates. Overall, there was a general lack of transparency in the studies and, consequently, the conclusions around the cost effectiveness of influenza vaccine in those aged 50-64 years must be interpreted with caution.

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