Timeliness of childhood immunisation in Australia
Introduction
Immunisation coverage at certain milestone ages in children is the most widely used indicator of the performance of immunisation programs, typically reported at 12 months, 24 months, and 4–6 years of age. The most widely accepted indicator internationally is the proportion of children who have received all recommended vaccines by 24 months of age, as prescribed by the World Health Organisation [1]. Such measures do not capture delay in the acquisition of immunity through late immunisation, which is especially important for a number of potentially severe infections of young infants such as pertussis and invasive disease due to Haemophilus influenzae type b or Streptococcus pneumoniae. Immunisation at the earliest appropriate age (timeliness) is an important public health goal, especially for countries where high levels of vaccine coverage at milestone ages have been achieved. However, timeliness of vaccine administration has received close attention only in the United States (US) [2], [3], [4], [5], [6], [7], [8], [9] with one study from Sweden [10]. Australia is uniquely well placed to monitor timeliness routinely and regularly because of its universal national childhood immunisation register, the Australian Childhood Immunisation Register (ACIR). The ACIR records immunisation data on all children under the age of 7 years enrolled in the Australian universal health insurance scheme, Medicare, and constitutes a nearly complete population register, as approximately 99% of the 250,000 children born each year are registered with Medicare by 12 months of age [11]. In this study, we report the degree of childhood vaccination delay in Australia with respect to time trends, age, vaccine, area of residence and Indigenous status and review this in the context of available data internationally.
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Methods
Immunisation data were obtained from the ACIR. The ACIR records notifications from providers of vaccinations received, and dates of administration. Date of birth, postcode of residence and Indigenous status are also recorded, although the latter is incomplete [12].
The primary outcome measure, age-appropriate immunisation, was defined as receipt of a scheduled vaccine dose within 30 days of the recommended age. So, a child who received the first dose of DTP (due at 60 days of age) when more than
Results
Timeliness of the first three doses of diphtheria, tetanus and pertussis (DTP) for the study cohort is shown in Fig. 1. The timeliness of receipt of DTP vaccines decreased by dose; 94.2% of children were on time for the first dose of DTP, declining to 75.6% by the third dose. Fig. 2 compares timeliness for the third dose of DTP for the study cohort (2001) with an identical sized cohort (1998). It demonstrates that there has been almost no change in timeliness of the third dose of DTP over time,
Discussion
Whilst timeliness of immunisation has been well studied in the US, primarily through studies derived from periodic National Immunisation Surveys [15], there is a dearth of information on timeliness elsewhere in the world (Table 3). Other countries such as the United Kingdom (UK) and some northern European countries have child immunisation data collection systems in place and publish immunisation coverage estimates but timeliness has been little studied, with only one regional study in Sweden
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2020, VaccineCitation Excerpt :Defining timeliness is challenging, we have used a definition of timeliness that is similar to that used in other studies and by the Centers for Disease Control [20,24,28,32,33]. Some studies used 30 days [24,25,33,34]. There are limitations to this study.