Evaluation of immunisation coverage for Aboriginal and Torres Strait Islander children using the Australian Childhood Immunisation Register

Objective: To estimate immunisation coverage for routinely administered vaccines among children using receipt of a particular Hib vaccine (PRP-OMP) as a proxy for Indigenous status. Methods: Until May 2000, PRP-OMP was provided only for Indigenous children in all jurisdictions except the Northern Territory. In three one-year ACIR-derived birth cohorts, any child recorded on the ACIR as receiving one or more doses of PRP-OMP as the only Hib vaccine was presumed to be Aboriginal and Torres Strait Islander. Using this proxy, estimated numbers of Indigenous children were compared with Australian Bureau of Statistics estimates, and immunisation status for recommended vaccines was estimated at 12 and 24 months by jurisdiction and remoteness compared with children who received other Hib vaccines (presumed non-Indigenous). Results: The numbers of Aboriginal and Torres Strait Islander children estimated using this 'proxy method' are approximately 42% of those estimated by the ABS. Immunisation coverage (among proxy Indigenous children) at 12 months (72–76%) and 24 months (64–73%) was considerably lower than others (90–94% and 81–88%, respectively). These children had significantly lower coverage when living in accessible areas than remote areas. Conclusions and Implications: These data provide the first national measure of immunisation status and are likely to be a valid measure among those identified. Aboriginal and Torres Strait Islander immunisation coverage is 17% lower with the biggest gaps in urban areas, indicating the need for better quality data informing appropriate interventions

Immunisation coverage in Australia corrected for under‐reporting to the Australian Childhood Immunisation Register

Abstract Objective: To assess the level of underreporting to the Australian Childhood Immunisation Register (ACIR) and the resulting underestimation of national immunisation coverage using ACIR data, and to correct national immunisation estimates for under‐reporting. Methods: A national population‐based telephone survey was conducted in May‐July 2001 of two random samples of children born in 1998 and 1999 who were recorded on the ACIR as incompletely immunised at either 12 months or 24 months of age. Parents were asked whether and when their child had received the vaccinations required to qualify as fully immunised. Survey data were then used to correct ACIR‐derived coverage estimates at 12 and 24 months of age. Results: Of 640 surveyed children in the 12‐month group, 258 (40%) met the study definition of ‘definitely immunised’. This adjusted the ACIR coverage estimate upwards by 2.7% to 94% (95% CI 93.6–94.1). Of 698 surveyed children in the 24‐month group, 387 (55%) met the study definition of ‘definitely immunised’ at the second birthday. Adjusted coverage for doses due by 24 months was 89.8% (95% CI 89.6–90.1), 5% higher than recorded on the ACIR. Conclusions: Immunisation coverage in Australia for all scheduled vaccines due by 12 months of age is 94% and for all vaccines due by two years of age is almost 90%. The ACIR underestimates coverage by up to 5%. As the ACIR database relies on provider notification, published estimates of immunisation coverage are unlikely to rise significantly above current levels, unless mechanisms are put in place to further improve notification to the ACIR

Measles vaccination coverage among five‐year‐old children: implications for disease elimination in Australia

Abstract Objectives:To (i) assess under‐reporting of measles‐mumps‐rubella (MMR) vaccinations to the Australian Childhood Immunisation Register (ACIR); (ii) estimate MMR coverage among five‐year‐old children and the proportion immune to measles infection; (iii) identify factors related to non‐uptake of MMR vaccination. Methods:We analysed ACIR data for a birth cohort of approximately 64,000 children aged five years. The parents of a sample of 506 children with no ACIR record for the second MMR vaccination (MMR2), due at four years of age, were interviewed by telephone to assess under‐reporting to the ACIR and reasons for non‐uptake of MMR vaccination. Results:Parents reported that 22% (n=111) of the surveyed 506 children had received MMR2 before their fifth birthday, and 42% (n=214) by ˜5.5 years of age. After correcting for this level of underreporting to the ACIR, MMR2 coverage for the entire cohort at five years of age was 52.9% (95% CI 52.3–53.4), and increased to 84.1% (95% CI 83.4–84.8) by ˜5.5 years of age. This was 4.3% and 8.2%, respectively, higher than ACIR coverage estimates at the two ages. Based on the corrected MMR coverage estimates, 93% of the cohort was immune to measles due to vaccination. The most common parent‐reported reason for incomplete vaccination was lack of knowledge about the MMR vaccination schedule. Conclusions:Measles elimination in Australia will require continued effort in vaccination coverage and timeliness among pre‐school children. School‐entry requirements are important for MMR2 uptake. Strategies are needed to improve reporting to the ACIR for more accurate measurement of coverage

Impact and effectiveness of childhood varicella vaccine program in Queensland, Australia

Background In November 2005, Australia introduced a publicly funded single dose of varicella vaccine for children aged 18-months. We describe the impact of this program on varicella hospitalisations in Queensland and provide the first assessment of single-dose varicella vaccine effectiveness in Australia since the program commenced. Methods Age-standardised varicella hospitalisation rates were calculated for 2000–2014 and pre- and post-public funding period rates compared. Case-control studies were conducted to investigate the association between vaccine receipt and both varicella hospitalisations and uncomplicated varicella emergency department presentations. Cases were matched to controls from a population-based register by date of birth and state of residence. Vaccine effectiveness was calculated as (1\ua0–\ua0odds ratio)\ua0×\ua0100%. Results Compared to the pre-funded period (2000–2003), age-standardised varicella hospitalisation rates declined by more than 70% in 2011–2014 with varicella principal diagnosis rates declining from 5.7 to 1.6 per 100,000 population per year. Varicella vaccine effectiveness at preventing hospitalisation with a principal diagnosis of varicella among children aged 19-months to 6-years was 81.9% (95% confidence interval: 61.8–91.4%), while for emergency department presentations among children aged 19-months to 8-years it was 57.9% (95% confidence interval: 48.5–65.5%). Conclusions In Australia, the single-dose varicella vaccination program has substantially reduced varicella morbidity. The single-dose varicella vaccine schedule is moderately-to-highly effective against hospitalisation, but appears less effective against emergency department presentations

Acellular pertussis vaccine effectiveness for children during the 2009-2010 pertussis epidemic in QueenslandAcellular pertussis vaccine effectiveness for children

OBJECTIVES To assess the effectiveness of three, four and five doses of acellular pertussis vaccine against pertussis notification for children aged 1 - < 4 years and 5 - < 12 years, and the effectiveness of three doses of acellular pertussis vaccine against pertussis hospitalisation for children aged 1 - < 4 years.A population-based retrospective study of children aged 1 - < 12 years residing in Queensland, Australia, during 2009 and 2010. Routinely collected notification, hospitalisation, testing and vaccination data were used to describe notification rates and testing patterns and to assess vaccine effectiveness (VE) by the screening method.VE against pertussis notification for children aged 1 - < 4 years and 5 - < 12 years, by birth year, and VE against pertussis hospitalisation for children aged 1 - < 4 years.1961 notifications and 29 hospitalisations were included in the VE calculations. VE point estimates against pertussis notification and hospitalisation in children aged 1 - < 4 years were similar in 2009 and 2010, and ranged between 83.5% and 89.4%. VE point estimates against notification among children aged 5 - < 12 years were between 71.2% and 87.7% in 2009, and between 34.7% and 70.3% in 2010. The numbers of pertussis tests performed for children, particularly polymerase chain reaction (PCR) tests, increased between 2009 and 2010.Acellular pertussis vaccine provided good protection within the first years of priming, but this waned as age increased. Changes in pertussis testing behaviour, because of increases in PCR use and awareness, may have contributed to increased pertussis notification rates and lower estimates of VE against notification owing to identification of milder disease

The Australian Measles Control Campaign, 1998

The 1998 Australian Measles Control Campaign had as its aim improved immunization coverage among children aged 1-12 years and, in the longer term, prevention of measles epidemics. The campaign included mass school-based measles-mumps-rubella vaccination of children aged 5-12 years and a catch-up programme for preschool children. More than 1.33 million children aged 5-12 years were vaccinated at school: serological monitoring showed that 94% of such children were protected after the campaign, whereas only 84% had been protected previously. Among preschool children aged 1-3.5 years the corresponding levels of protection were 89% and 82%. During the six months following the campaign there was a marked reduction in the number of measles cases among children in targeted age groups