Probabilistic linkage of national immunisation and state-based health records for a cohort of 1.9 million births to evaluate Australia’s childhood immunisation program

Abstract

IntroductionSeveral countries have developed national immunisation registers, but only the Nordic countries have linked their registers to other health data in order to comprehensively evaluate the 'real world' effectiveness of vaccines. Nordic countries can link datasets deterministically using the national person identifier, but most countries, including Australia, don't have such an identifier to enable this type of linkage.

Assessment of on-time vaccination coverage in population subgroups: A record linkage cohort study

“…The full details of assembling the linked dataset through probabilistic linkage across three linkage centres are provided elsewhere. [8,9] In brief, the cohort comprised 1,953,881 infants that had both a registered birth record and a perinatal data record. Aboriginal status was derived using a multi-stage median algorithm, described previously [10] using information from all linked datasets in the study, excluding deaths, and based on Australia's national best practice guidelines for data linkage activities relating to Aboriginal and Torres Strait Islander people.…”

“…DTP immunisation records for the study cohort between 1996 and 2013 were extracted from AIR and probabilistically linked at the Australian Institute of Health and Welfare as described previously. [8,9] In brief, immunisation data from AIR were linked to the birth register based on a matched linkage rate of 99.3% (similar to a sensitivity measure) with a corresponding linkage accuracy of 99.0% (similar to a positive predictive value measure). Duplicate immunisation records with the same immunisation date and vaccine dose number were removed.…”

Use of data linkage to improve communicable disease surveillance and control in Australia: existing practices, barriers and enablers

“…Despite this, gaps in surveillance data remain, 2,3,7 impacting on the system’s utility to support the development of evidence‐based prevention and control efforts. Data linkage is recognised as a valuable method to close surveillance gaps and enhance the value of publicly held health data 10,24,48,61,62 . To our knowledge, this is the first time that jurisdictional practices relating to the use of data linkage in the communicable disease setting in Australia have been described.…”

“…In our study, none of the jurisdictions reported using data linkage methodologies to improve vaccination status in local notifiable disease registries. We contend, that while the use of data linkage may not be practicable during an immediate public health response, gaps in surveillance data relating to vaccination status could be addressed retrospectively to improve completeness of this key variable in local and national surveillance systems, thereby also improving cross‐jurisdictional evaluation of national immunisation programs 24 . Using the AIR in this manner would accord with the stated purposes of the register as set out in the Australian Immunisation Register Act 47 .…”

“…In the communicable diseases setting, data linkage can be used to evaluate public health interventions and guide policy development 14 . In Australia, data linkage methodologies have been used to quantify case ascertainment in communicable disease registers; 15 to improve estimates of selected communicable diseases; 16–19 to better describe the burden of selected communicable diseases among Aboriginal and Torres Strait Islander people; 3–5,20 to improve communicable disease morbidity and mortality estimates; 21–23 and to evaluate immunisation programs 24–27 . These are all important examples of how data linkage can be applied to support communicable disease research in Australia, and results from these studies are often used to inform policy making and program improvement 14 .…”