Suchergebnisse

IntroductionImmunisation coverage is a good measure of immunisation program effectiveness. Coverage of the 3-dose infant schedule in Australia assessed at age 12 months is >90%. Timeliness is an important goal for population immunity, but on-time coverage of the 2-4-6 month schedule and coverage in specific populations is rarely reported.
Objectives and ApproachWe conducted a retrospective population-based cohort study of 1.9 million Australian births, 1996-2012 (approximately 42% of Australia's population). Individual data from state-held birth and perinatal records were combined with Commonwealth-held immunisation and death records, through probabilistic linkage. We assessed on-time coverage across 13 demographic and perinatal characteristics of diphtheria-tetanus-pertussis vaccines (DTP) defined as vaccination 14 days prior to the scheduled due date, to 30 days afterwards.
ResultsOn-time DTP vaccination coverage in non-Aboriginal infants was 88.1% for the 2-month dose, 82.0% for 4-month dose, and 76.7% for 6-month dose; 3-dose coverage was 91.3% when assessed at 12 months. On-time DTP coverage for Aboriginal infants was 77.0%, 66.5%, and 61.0%; 3-dose coverage at 12 months was 79.3%. Appreciable differences in on-time coverage were observed across population subgroups. On-time coverage in non-Aboriginal infants born to mothers with ≥3 previous pregnancies was 62.5% for the 6-month dose (47.9% for Aboriginal infants); up to 23.5% lower than for first-borns. Infants born to mothers who smoked during pregnancy had coverage 8.7-10.3% lower than infants born to non-smoking mothers for the 4- and 6-month dose. A linear relationship was apparent with increasing socio-economic disadvantage and decreasing on-time coverage.
Conclusion/ImplicationsOn-time vaccination coverage of the 2-4-6 month schedule is only 50-60% across specific population subgroups representing a significant avoidable public health risk. Australian Aboriginal infants, multiparous mothers, and those who are socio-economically disadvantaged are key groups most likely to benefit from targeted programs addressing vaccine timeliness.

ABSTRACT
ObjectiveImmunisation remains one of the most important public health interventions. However, linkage of population-based immunisation registers to perinatal and health outcome datasets to evaluate immunisation programs is limited. We have conducted the first-ever linkages of immunisation records from Australia's Childhood Immunisation Register (ACIR) for the purposes of evaluating Australia's unique national immunisation program. As an initial outcome of our linkage study we present estimates of pneumococcal conjugate vaccine (PCV) coverage for the 3rd dose assessed at 12 months of age in extremely preterm children (gestational age <28 weeks), in whom a funded vaccination program was established in 2001 prior to a universal funded program for all children in 2005.
ApproachIndividual immunisation records from ACIR, hospital admissions, deaths and infectious diseases notifications were linked to perinatal records for a cohort of births from 1996 to 2012 in two Australian states. Three separate data linkage units were involved in the process with varying procedures for linkage. The perinatal datasets were used to identify extremely preterm children.
ResultsThe birth cohort for the study included 1,958,537 live births in New South Wales (1,492,399) and Western Australia (461,620). Linkage weights based on sensitivity and positive predictive value of >99% were used to identify immunisation records from ACIR to link to the birth cohort. A unique scrambled pin on ACIR was used to link immunisation records to birth cohort datasets. The final cohort consisted of 1,954,019 children with 95.5% linking to at least 1 ACIR record from a total of >26.6 million ACIR records. In 2001, coverage of the 3rd dose of PCV in extremely preterm children was 0.9% and increased to 69.1% in 2004 (overall coverage 2001-2004: 25.3%). From 2005 to 2012, coverage increased to an average of 89.7%.
ConclusionThese are the first results of cross-jurisdictional linkages of immunisation records to state-based administrative datasets in Australia. This process has identified some improvements that are needed to streamline future linkage projects of this scale. Linkage of perinatal datasets to ACIR has enabled us to assess the first-ever coverage estimates in specific medically at-risk population subgroups. Future analyses will focus on the predictors and timeliness of vaccination coverage and population based estimates of vaccine effectiveness.

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.