This research report presents exploratory analysis of coverage estimates of vaccines/antigens assessed at the 2-year and 5-year age milestone and factors contributing to lower ‘fully vaccinated’ coverage at the 2-year age milestone than at the 5-year age milestone.

NCIRS conducted an exploratory analysis of adult vaccination data for selected vaccines recorded on the Australian Immunisation Register (AIR) for the first 2 years of its establishment (October 2016 – September 2018). This research aims to inform continuous improvement of AIR data to evaluate the National Immunisation Program (NIP) outcomes and to provide improved information and feedback to providers and patients.

This summary report presents key findings from the Annual Immunisation Coverage Report 2018 which focussed on changes in immunisation coverage among all children aged <5 years at key milestone ages of 12, 24 and 60 months between 2017 and 2018.

The Annual Immunisation Coverage Report 2018 is the 12th in the series, and shows data for the calendar year 2018 derived from the Australian Immunisation Register for all children aged <5 years. The report focusses on changes in vaccination coverage at key milestone ages of 12, 24 and 60 months between 2017 and 2018, but also documents longer term trends. ‘Fully vaccinated’ coverage increased at the 12- and 60-month milestones to 93.9% and 94.0%, respectively, but, in the context of additional antigens required, decreased to 90.1% at 24 months.

This study represents the first attempt to systematically audit the accuracy of AIR data at the national level since 2001. Of the 905 records included in the final analysis, 86% were assessed as accurate (truly overdue) and 14% as inaccurate (i.e. the child appeared overdue despite being actually up to date for the relevant antigen). The error rate ranged from 3% in Victoria to 29% in New South Wales.