Impact of the national targeted Hepatitis A immunisation program in Australia: 2000-2014

In November 2005, hepatitis A vaccine was funded under the Australian National Immunisation Program for Aboriginal and Torres Strait Islander (Indigenous) children aged 12-24months in the targeted jurisdictions of Queensland, South Australia, Western Australia and the Northern Territory. We reviewed the epidemiology of hepatitis A from 2000 to 2014 using data from the Australian National Notifiable Diseases Surveillance System, the National Hospital Morbidity Database, and Australian Bureau of Statistics causes-of-death data. The impact of the national hepatitis A immunisation program was assessed by comparison of pre-vaccine (2000-2005) and post-vaccine time periods (2006-2014), by age group, Indigenous status and jurisdiction using incidence rate ratios (IRR) per 100,000 population and 95% confidence intervals (CI). The national pre-vaccine notification rate in Indigenous people was four times higher than the non-Indigenous rate, and declined from 8.41 per 100,000 (95% CI 5.03-11.79) pre-vaccine to 0.85 per 100,000 (95% CI 0.00-1.99) post-vaccine, becoming similar to the non-Indigenous rate. Notification and hospitalisation rates in Indigenous children aged <5years from targeted jurisdictions declined in the post-vaccine period when compared to the pre-vaccine period (notifications: IRR=0.07; 95% CI 0.04-0.13; hospitalisations: IRR=0.04; 95% CI 0.01-0.16). As did notification rates in Indigenous people aged 5-19 (IRR=0.08; 95% CI 0.05-0.13) and 20-49years (IRR=0.06; 95% CI 0.02-0.15) in targeted jurisdictions. For non-Indigenous people from targeted jurisdictions, notification rates decreased significantly in children aged <5years (IRR 0.47; 95% CI 0.31-0.71), and significantly more overall (IRR=0.43; 95% CI 0.39-0.47) compared to non-Indigenous people from non-targeted jurisdictions (IRR=0.60; 95% CI 0.56-0.64). The national hepatitis A immunisation program has had a significant impact in the targeted population with relatively modest vaccine coverage, with evidence suggestive of substantial herd protection effects.