Some truths about the “low” childhood vaccination coverage in Sydney’s eastern suburbs

Among the hype and controversy prompted by the Australian Government’s recent announcement that conscientious objectors to childhood vaccination would lose childcare subsidies and part of the family tax benefit,1 including the accompanying media rancour,2 it is worth noting that published vaccination coverage figures based on the Australian Childhood Immunisation Register (the Register) are only an estimate of the extent of coverage. In the case of the eastern suburbs of Sydney, they significantly underestimate the true coverage.

In January 2002, we studied a cohort of children aged between 12 and less than 15 months residing in south-eastern Sydney; according to the Register, 81% had received all vaccination doses scheduled for the first year of life. Systematic follow-up — by contacting providers and/or parents — of one-third of the children recorded by the Register as being overdue for one or more do ses established that the overall proportion of children who were up-to-date with their vaccinations was, in fact, at least 91%.3

In March 2013, we undertook a similar follow-up survey, on this occasion focusing on children aged between 12 and less than 15 months who resided in the Waverley and Sydney City local government areas, where the Register-based coverage level was reported as being 87%. These areas were targeted because this figure was significantly lower than the overall south-eastern Sydney figure of 91%. Of 112 children recorded as being overdue for one or more vaccinations and whose records were checked with providers and parents, 37 (33%) were actually up-to-date, leading to an increase of 4% in the estimated total coverage, to at least 91%.

Although there is evidence of underreporting of childhood vaccinations in urban areas,4 the purportedly low childhood vaccination coverage in parts of Sydney has been cited critically on a number of occasions, including in the New South Wales parliament.5 On the basis of our follow-up surveys, which we have continued since 2013 in collaboration with Medicare Locals, we have established that published coverage rates based on Register data are significantly underestimated.

Discussions with medical practice staff and support officers suggest that in many instances where children have been incorrectly recorded in the Register as being overdue for vaccinations, it is because general practitioners do not understand the reporting process, data have been entered incorrectly, or there are technical problems in the practice software that transmits encounter data to the Register.

In some localities, including ours, the true level of coverage is higher than that reflected in the Register. It then becomes a public health priority to identify those populations where coverage is genuinely low, so that education and other appropriate efforts can be properly focused. To obtain a more accurate picture of variations in coverage, investment is required to provide ongoing support to general practice staff and to ensure that practice software interfaces seamlessly with the Register.