Harnessing routinely collected data for effective control of vaccine preventable disease in Australia.

Abstract

The primary goal of the Australian Government Department of Health's (DoH) Immunisation Branch (IB) is to protect Australians from vaccine preventable diseases (VPDs) primarily via the administration of the National Immunisation Program (NIP). The NIP has, since its birth in 1998 been credited with significant gains in childhood immunisation coverage across Australia. Despite this, there remain under-vaccinated pockets of the population vulnerable to outbreaks of VPDs. Good quality data and its appropriate use is key to informing policies and programs aimed at lifting vaccination uptake and in the control of VPDs. In the projects of this thesis, each of which was conducted to achieve core requirements of the Master of Philosophy in Applied Epidemiology (MAE), routinely collected data are leveraged to answer immunisation policy and programming questions and to investigate an epidemic of a VPD. Australia has a valuable central repository for vaccination-related information for its residents, the Australian Immunisation Register (AIR). The dataset has long been used for administrative and social service purposes by the Department of Human Services (DHS); however it is also an important surveillance and public health instrument. The DoH recently received a subset of the register in order to allow the IB to undertake real-time analytics to better support program and policy-making decisions and prescribed bodies on data related matters.This project (AIR data access reform) is poised to undertake its second phase, the roll-out of the DoH AIR data to States/Territories which sets the stage for the evaluation requirement of the MAE. I evaluate the usefulness of the health AIR dataset for States/Territories to meet their immunisation and public health goals (Chapter 5). The evaluation finds a need for a transparent, consistent approach to the use of AIR data and a community of practice that offers ongoing technical support. AIR data access has enabled a further two projects included in this thesis. The first is an historical review of immunisation medical exemptions (IMEs) registered in the AIR in which trends overtime particularly around key policy changes are explored (Chapter 3). We find evidence that policies linking financial incentives to immunisation status do impact IME rates which reflects responses both by immunisation providers and families. We also discover that the observed rise in IME rates following one policy change is curbed by tighter rules around IME granting. In Chapter 4, AIR-derived routine immunisation coverage data is used to evaluate the impact of a national education campaign aimed at increasing childhood vaccination demand, particularly in areas of low coverage. Using an interrupted-time-series design we find a positive impact in several targeted areas and discover that success of the campaign did not vary by small-area-level socioeconomic rating, vaccination objection level or remoteness. Continuing the theme of VPD prevention, for the outbreak requirement (Chapter 2), I investigate together with New South Wales (NSW) Health the factors associated with influenza infection in a summer epidemic (2018-2019) by utilising the NSW notifiable disease database as a platform for the distribution of a survey via text message. This case control study reveals that international travel and/or contact with an ill traveller in the week prior to becoming ill was strongly associated with influenza in the first two months of summer. This thesis focuses on immunisation in Australia; the projects hinge on the optimal use of large datasets and database platforms to help inform the control of VPDs at a time in which the DoH is expanding data access and analytic capabilities. Findings may assist with DoH understanding of the impacts of key immunisation interventions and policies, contribute to the relevant literature, feed discussion on pre-travel vaccination practices and help guide further steps in immunisation data sharing.