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

In: International journal of population data science: (IJPDS), Band 2, Heft 1

Abstract

IntroductionSeveral countries have developed national immunisation registers, but only the Nordic countrieshave 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 nationalperson identifier, but most countries, including Australia, don't have such an identifier to enablethis type of linkage.
ObjectivesTo describe the process for assembling a linked study cohort that will enable the conduct ofpopulation-based studies related to immunisation and immunisation policy.
MethodsNational death and immunisation databases along with state health data (notifications of vaccinepreventable diseases, perinatal data, hospital admissions and emergency department presentations)up until December 2013 were probabilistically linked (using demographic details) for children bornbetween 1996 and 2012 in two states: Western Australia and New South Wales (42% of Australia'spopulation, combined).
ResultsAfter exclusions there were 1.95 million children in the study cohort (live born children withboth a birth and perinatal record which represents 97.5% of all live births in the state perinataldata collections - our source population) and 18.0 million person years of follow up (mean: 9.2years per child). The characteristics of children in the cohort were generally similar to those onlyincluded in state perinatal databases and outcome measures were in keeping with expected figuresfrom unlinked data sources. However, the lack of a dynamic national population register meantimmigrants could not be included.
ConclusionsWe have been able to develop a similarly comprehensive system to the Nordic countries based onprobabilistic linkage methods. Our experience should provide encouragement to other countrieswith national immunisation registers looking to establish similar systems.