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We conducted probabilistic data linkage of three population datasets for the Northern Territory (NT), Australia, to describe the incidence of preterm births, stillbirths, low birthweight and small for gestational age (SGA) per 1000 NT births; and influenza and pertussis hospitalisations per 1 00 000 NT births in infants <7 months of age, in a pre-maternal vaccination era. The Perinatal Trends dataset (1994-2014) formed the cohort of 78 382 births. Aboriginal mother-infant pairs (37%) had disproportionately higher average annual rates (AR) for all adverse birth outcomes compared to their non-Aboriginal counterparts; rate ratios: preterm births 2.2 (AR 142.4 vs. 64.7); stillbirths 2.3 (AR 10.8 vs. 4.6); low birthweight 2.9 (AR 54 vs. 19); and SGA 1.7 (AR 187 vs. 111). Hospitalisation (2000-2015) and Immunisation Register datasets (1994-2015), showed that influenza hospitalisations (n = 53) and rates were 42.3 times higher in Aboriginal infants (AR 254 vs. 6); and that pertussis hospitalisations (n = 37) were 7.1 times higher in Aboriginal infants (AR 142.5 vs. 20.2) compared to non-Aboriginal infants. These baseline data are essential to assess the safety and effectiveness of influenza and pertussis vaccinations in pregnant women from the NT. Remote living Aboriginal women and infants stand to benefit the most from these vaccines.

Prevalence of skin sores and scabies in remote Australian Aboriginal communities remains unacceptably high, with Group A Streptococcus (GAS) the dominant pathogen. We aim to better understand the drivers of GAS transmission using mathematical models. To estimate the force of infection, we quantified the age of first skin sores and scabies infection by pooling historical data from three studies conducted across five remote Aboriginal communities for children born between 2001 and 2005. We estimated the age of the first infection using the Kaplan-Meier estimator; parametric exponential mixture model; and Cox proportional hazards. For skin sores, the mean age of the first infection was approximately 10 months and the median was 7 months, with some heterogeneity in median observed by the community. For scabies, the mean age of the first infection was approximately 9 months and the median was 8 months, with significant heterogeneity by the community and an enhanced risk for children born between October and December. The young age of the first infection with skin sores and scabies reflects the high disease burden in these communities.

Pertussis morbidity is highest in infants too young to be fully protected by routine vaccination schedules. Alternate vaccine strategies are required to maximise protection in this age-group. To understand baseline pertussis epidemiology prior to the introduction of the maternal pertussis vaccination program in 2014, we conducted a retrospective case series analyses of 53 901 notifications and temporal trends from 1997 to 2014. Notifications were highest in infants younger than 4 months of age and highest annual notification rates in infants younger than 1 month of age (308/100 000 per year). Amongst Aboriginal and Torres Strait Islander infants aged younger than 1 month, this rate was 576/100 000 per year. Notification rates were 40% higher amongst women 15-44 years, 62·4/100 000 population compared with men (44·5/100 000) and 90% higher in Aboriginal and Torres Strait Islander women of the same age (38·2/100 000) compared with men (19·7/100 000). Six infant deaths were identified, all younger than 2 months of age. Monitoring epidemiology in at-risk groups - infants too young to be vaccinated, women of childbearing age and Aboriginal and Torres Strait Islander peoples - following implementation of the maternal pertussis vaccination program will be important to assess its impact and safety.

This study describes the epidemiology of community-acquired pneumonia (CAP) in elderly Australians for the first time. Using a case-cohort design, cases with CAP were in-patients aged > or = 65 years with ICD-10-AM codes J10-J18 admitted over 2 years to two tertiary hospitals. The cohort sample was randomly selected from all hospital discharges, frequency-matched to cases by month. Logistic regression was used to estimate risk ratios for factors predicting CAP or associated mortality. A total of 4772 in-patients were studied. There were 1952 cases with CAP that represented 4% of all elderly admissions: mean length of stay was 9.0 days and 30-day mortality was 18%. Excluding chest radiograph, 520/1864 (28%) cases had no investigations performed. The strongest predictors of CAP were previous pneumonia, history of other respiratory disease, and aspiration. Intensive-care-unit admission, renal disease and increasing age were the strongest predictors of mortality, while influenza vaccination conferred protection. Hospitalization with CAP in the elderly is common, frequently fatal and a considerable burden to the Australian community. Investigation is ad hoc and management empirical. Influenza vaccination is associated with reduced mortality. Patient characteristics can predict risk of CAP and subsequent mortality.

Invasive pneumococcal disease (IPD) notifications are used to monitor IPD vaccination programmes. We conducted sequential deterministic data-linkage between IPD notifications and hospitalization data in Victoria, Australia, in order to determine whether all diagnosed cases were being reported. The proportion of each relevant hospital admission ICD-10-AM code that could be linked to notified cases was calculated. Total and age-specific annual rates were calculated and compared for notified and non-notified cases. Total incidence was estimated using data-linkage results and application of a two-source capture-recapture method. The first 2 years of IPD surveillance in Victoria missed at least one-sixth of laboratory-confirmed IPD cases. Estimated annual IPD rate increased from 9.0 to 10.7/100,000 and rose even higher, to 11.5/100,000, with age-specific rates possibly reaching 90.0/100,000 children aged <2 years, when using capture-recapture. Strategies to improve notification and coding of hospitalized cases of IPD are required.

This study examines the validity of using ICD-10 codes to identify hospitalized pneumonia cases. Using a case-cohort design, subjects were randomly selected from monthly cohorts of patients aged > or = 65 years discharged from April 2000 to March 2002 from two large tertiary Australian hospitals. Cases had ICD-10-AM codes J10-J18 (pneumonia); the cohort sample was randomly selected from all discharges, frequency matched to cases by month. Codes were validated against three comparators: medical record notation of pneumonia, chest radiograph (CXR) report and both. Notation of pneumonia was determined for 5098/5101 eligible patients, and CXR reports reviewed for 3349/3464 (97%) patients with a CXR. Coding performed best against notation of pneumonia: kappa 0.95, sensitivity 97.8% (95% CI 97.1-98.3), specificity 96.9% (95% CI 96.2-97.5), positive predictive value (PPV) 96.2% (95% CI 95.4-97.0) and negative predictive value (NPV) 98.2% (95% CI 97.6-98.6). When medical record notation of pneumonia is used as the standard, ICD-10 codes are a valid method for retrospective ascertainment of hospitalized pneumonia cases and appear superior to use of complexes of symptoms and signs, or radiology reports.

For jurisdictions implementing measles elimination strategies, a minimum surveillance benchmark of 1/100 000 population per year measles-like illness (MLI) cases initially notified, but then rejected based on laboratory testing was proposed. We used this standard to assess the quality of the Victorian enhanced measles surveillance between 1998 and 2003. Victorian enhanced measles surveillance includes interviews with notified cases and confirmatory laboratory testing for notifications. We found 72% (918/1281) of measles notifications were discarded after testing. The median annual rate of discard was 2.9/100 000. The annual discard rate was inversely associated with the age of the notifications, and measles negative with no other diagnosis made was the most common laboratory outcome. The annual rates of discarded notifications in Victoria were consistently above the minimum recommended standard. The rate of discarded MLIs as a surveillance threshold should be useful in measles endemic regions, but may require modification where disease elimination has occurred.

In Victoria (Australia) surveillance for mumps and rubella has historically been passive, with most notified cases clinically diagnosed. In July 2001, the Victorian Department of Human Services implemented an enhanced surveillance system focusing on improved laboratory testing. We tested 85% of notifications and only 9% of all mumps and 27% of rubella notifications were laboratory confirmed. While most notified cases were children who had been clinically diagnosed, we found most laboratory-confirmed cases were in adults. The positive predictive value of the clinical case definition was low: mumps (10%); rubella (22%). These results highlight the value of laboratory confirmation of the diagnosis when mumps and rubella are rare, failure to do so is likely to overestimate disease incidence.