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Abstract Background The need for coronavirus 2019 (COVID-19) vaccination in different age groups and populations is a subject of great uncertainty and an ongoing global debate. Critical knowledge gaps regarding COVID-19 vaccination include the duration of protection offered by different priming and booster vaccination regimens in different populations, including homologous or heterologous schedules; how vaccination impacts key elements of the immune system; how this is modified by prior or subsequent exposure to severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) and future variants; and how immune responses correlate with protection against infection and disease, including antibodies and effector and T cell central memory. Methods The Platform Trial In COVID-19 priming and BOOsting (PICOBOO) is a multi-site, multi-arm, Bayesian, adaptive, randomised controlled platform trial. PICOBOO will expeditiously generate and translate high-quality evidence of the immunogenicity, reactogenicity and cross-protection of different COVID-19 priming and booster vaccination strategies against SARS-CoV-2 and its variants/subvariants, specific to the Australian context. While the platform is designed to be vaccine agnostic, participants will be randomised to one of three vaccines at trial commencement, including Pfizer’s Comirnaty, Moderna’s Spikevax or Novavax’s Nuvaxovid COVID-19 vaccine. The protocol structure specifying PICOBOO is modular and hierarchical. Here, we describe the Core Protocol, which outlines the trial processes applicable to all study participants included in the platform trial. Discussion PICOBOO is the first adaptive platform trial evaluating different COVID-19 priming and booster vaccination strategies in Australia, and one of the few established internationally, that is designed to generate high-quality evidence to inform immunisation practice and policy. The modular, hierarchical protocol structure is intended to standardise outcomes, endpoints, data collection and other study processes for nested substudies included in the trial platform and to minimise duplication. It is anticipated that this flexible trial structure will enable investigators to respond with agility to new research questions as they arise, such as the utility of new vaccines (such as bivalent, or SARS-CoV-2 variant-specific vaccines) as they become available for use. Trial registration Australian and New Zealand Clinical Trials Registry ACTRN12622000238774. Registered on 10 February 2022.

Abstract As COVID-19 vaccinations rolled out globally from late 2020, rules and recommendations regarding vaccine use in pregnancy shifted rapidly. Pre-registration COVID-19 vaccine trials excluded those who were pregnant. Initial Australian medical advice did not routinely recommend COVID-19 vaccines in pregnancy, due to limited safety data and little perceived risk of local transmission. Advice from local medical authorities changed throughout 2021, however, with recommendations and priority access during pregnancy. In Western Australia (WA), recommendations became requirements as the State government mandated vaccines for some workers, with brief availability of pregnancy exemptions. Through an examination of 10 in-depth interviews with WA pregnant women, we explore their decision-making and complex emotions regarding COVID-19 vaccinations, and how they balanced mandates, recommendations, and shifting considerations and perceptions of risk. Changing recommendations and rules—and media and popular interpretation and communications of these—led to confusion, including for medical professionals. Expectant parents had to negotiate the risks of COVID-19 disease, potential benefits and risks of vaccination, professional and personal costs of vaccine refusal, and interpret mixed medical advice. Our findings can inform the development and communication of public health policies and medical advice, and contribute to our understanding of bodily autonomy, risk, and decision-making beyond the pandemic.

Abstract Background Australian children and adolescents were among the last local cohorts offered COVID-19 vaccines. Despite promising initial uptake, coverage subsequently plateaued, requiring further efforts to improve access and build parents’ recognition of the importance of COVID-19 vaccination. We sought to understand West Australian (WA) parents’ willingness to vaccinate their children to inform strategies for improving uptake at the time in which they were becoming eligible. Methods We undertook in-depth qualitative interviews with 30 parents of children aged 5–17 years from June – December 2021. During this period, children aged 12–15 years became eligible for vaccination; children aged 5–11 years became eligible shortly thereafter. Data were thematically analysed in NVivo. Results Most parents intended on vaccinating their children once eligible. Parents sought to protect their children, to protect the community, to resume travel, and to get back to “normal”. They reflected that vaccination against key infectious threats is a routine activity in childhood. Some were concerned about the vaccine, particularly mRNA vaccines, being new technology or impacting fertility. “Wait-awhiles” wanted to see what other parents would do or were delaying until they felt that there was a higher risk of COVID-19 in WA. Most parents of younger children wanted their child to be vaccinated at the general practice clinic due to familiarity and convenience. Parents were particularly eager for clear and consistent messaging about vaccination of children and adolescents, including safety, importance, scientific evidence, and personal stories. Conclusion For future pandemic vaccinations pertaining to children, governments and health officials need to address parents’ concerns and meet their preferences for the delivery of the vaccine program to children and adolescents.

Summary: Background: Pneumonia is the leading cause of death in young children globally and is prevalent in the Papua New Guinea highlands. We investigated clinical predictors of hypoxic pneumonia to inform local treatment guidelines in this resource-limited setting. Methods: Between 2013 and 2020, two consecutive prospective observational studies were undertaken enrolling children 0–4 years presenting with pneumonia to health-care facilities in Goroka Town, Eastern Highlands Province. Logistic regression models were developed to identify clinical predictors of hypoxic pneumonia (oxygen saturation

Introduction Children with chronic medical diseases are at an unacceptable risk of hospitalisation and death from influenza and SARS-CoV-2 infections. Over the past two decades, behavioural scientists have learnt how to design non-coercive ‘nudge’ interventions to encourage positive health behaviours. Our study aims to evaluate the impact of multicomponent nudge interventions on the uptake of COVID-19 and influenza vaccines in medically at-risk children.Methods and analyses Two separate randomised controlled trials (RCTs), each with 1038 children, will enrol a total of approximately 2076 children with chronic medical conditions who are attending tertiary hospitals in South Australia, Western Australia and Victoria. Participants will be randomly assigned (1:1) to the standard care or intervention group. The nudge intervention in each RCT will consist of three text message reminders with four behavioural nudges including (1) social norm messages, (2) different messengers through links to short educational videos from a paediatrician, medically at-risk child and parent and nurse, (3) a pledge to have their child or themselves vaccinated and (4) information salience through links to the current guidelines and vaccine safety information. The primary outcome is the proportion of medically at-risk children who receive at least one dose of vaccine within 3 months of randomisation. Logistic regression analysis will be performed to determine the effect of the intervention on the probability of vaccination uptake.Ethics and dissemination The protocol and study documents have been reviewed and approved by the Women’s and Children’s Health Network Human Research Ethics Committee (HREC/22/WCHN/2022/00082). The results will be published via peer-reviewed journals and presented at scientific meetings and public forums.Trial registration number NCT05613751.

Introduction Acute respiratory infections (ARI) are the most common cause of paediatric hospitalisation. There is an urgent need to address ongoing critical knowledge gaps in ARI management. The Pragmatic Adaptive Trial for Respiratory Infections in Children (PATRIC) Clinical Registry will evaluate current treatments and outcomes for ARI in a variety of paediatric patient groups. The registry will provide a platform and data to inform a number of PATRIC clinical trials, testing various interventions in ARI treatment and management to optimise paediatric ARI care.Methods and analysis The PATRIC Clinical Registry is a single-centre, prospective observational registry recruiting from a tertiary paediatric Emergency Department in Western Australia. Through characterising demographic, clinical, treatment and outcome data, the PATRIC Clinical Registry will improve our understanding of antibiotic utilisation and ARI outcomes in children.Ethics and dissemination The PATRIC Clinical Registry is conducted in accordance with the Declaration of Helsinki, and the International Council for Harmonisation (ICH) Guidelines for Good Clinical Practice (CPMP/ICH/13595) July 1996. Approval is provided by the Child and Adolescent Health Service Human Research Ethics Committee (HREC). Study results will be communicated by presentation and publication (HREC: RGS0000003078.)Trial registration number Australian New Zealand Clinical Trials Registry (ANZCTR): ACTRN12619000903189. UTN: U1111-1231-3365.

Introduction: To assess potential benefits and direct healthcare cost savings with expansion of an existing childhood influenza immunisation program, we developed a dynamic transmission model for the state of Western Australia, evaluating increasing coverage in children $A1.5 million dollars were observed for every 10 % increase in vaccine coverage in children

The incidence of respiratory syncytial virus (RSV) in adults is inadequately defined and the impact of SARS-CoV-2-related non-pharmaceutical interventions (NPIs) is underexplored. Using laboratory data, we described the detection rate of RSV in adults ≥16 years in Western Australia (WA) between 2017 and 2023. With the exception of 2020, RSV detections rose annually between 2017 and 2023, reaching 50.7 per 100,000 in 2023 (95% confidence interval [CI], 47.9–53.8). RSV testing expanded considerably across the study period, with the testing in 2023 more than five times the 2017 total. The detection rate was highest in adults ≥60 years between 2017 and 2019, particularly those ≥75 years. Following 2020, the detections in all age groups increased, with the highest detection rate in 2023 in those ≥75-years (199.5 per 100,000; 95% CI, 180.5–220). NPIs significantly impacted RSV seasonality; the preceding winter pattern was disrupted, resulting in an absent 2020 winter season and two major summer seasons in 2020/21 and 2021/22. The RSV season began to realign in 2022, reverting to a winter seasonal pattern in 2023 and the largest season in the study period. Ongoing surveillance will be required to understand the stability of these increases and to delineate the impact of new immunisation strategies.

Respiratory syncytial virus (RSV) reinfection in children is poorly understood. We examined the incidence, characteristics, and outcomes of hospital-attended RSV reinfections in children

Abstract Respiratory syncytial virus (RSV) is a leading cause of childhood morbidity, however there is no systematic testing in children hospitalised with respiratory symptoms. Therefore, current RSV incidence likely underestimates the true burden. We used probabilistically linked perinatal, hospital, and laboratory records of 321,825 children born in Western Australia (WA), 2000–2012. We generated a predictive model for RSV positivity in hospitalised children aged

Background: Rotavirus vaccination was introduced into the Australian National Immunisation Program in mid-2007. We aimed to assess the impact of the rotavirus vaccination program on the burden of hospitalizations associated with all-cause acute gastroenteritis (including rotavirus gastroenteritis and non-rotavirus gastroenteritis) in the Aboriginal and non-Aboriginal population in Western Australia. Methods: We identified all hospital records, between July 2004 and June 2012, with a discharge diagnosis code for all-cause gastroenteritis. Age-specific hospitalization rates for rotavirus and non-rotavirus acute gastroenteritis before and after the introduction of the rotavirus vaccination program were compared. Interrupted time-series models were used to examine differences in the annual trends of all-cause gastroenteritis hospitalization between the two periods. Results: Between July 2004 and June 2012, there were a total of 106,974 all-cause gastroenteritis-coded hospitalizations (1,381 rotavirus-coded [15% among Aboriginal] and 105,593 non-rotavirus gastroenteritis-coded [7% among Aboriginal]). Following rotavirus vaccination introduction, significant reductions in rotavirus-coded hospitalization rates were observed in all children aged

Scedosporium spp. are the second most prevalent filamentous fungi after Aspergillus spp. recovered from cystic fibrosis (CF) patients in various regions of the world. Although invasive infection is uncommon prior to lung transplantation, fungal colonization may be a risk factor for invasive disease with attendant high mortality post-transplantation. Abundant in the environment, Scedosporium aurantiacum has emerged as an important fungal pathogen in a range of clinical settings. To investigate the population genetic structure of S. aurantiacum, a MultiLocus Sequence Typing (MLST) scheme was developed, screening 24 genetic loci for polymorphisms on a tester strain set. The six most polymorphic loci were selected to form the S. aurantiacum MLST scheme: actin (ACT), calmodulin (CAL), elongation factor-1α (EF1α), RNA polymerase subunit II (RPB2), manganese superoxide dismutase (SOD2), and β-tubulin (TUB). Among 188 global clinical, veterinary, and environmental strains, 5 to 18 variable sites per locus were revealed, resulting in 8 to 23 alleles per locus. MLST analysis observed a markedly high genetic diversity, reflected by 159 unique sequence types. Network analysis revealed a separation between Australian and non-Australian strains. Phylogenetic analysis showed two major clusters, indicating correlation with geographic origin. Linkage disequilibrium analysis revealed evidence of recombination. There was no clustering according to the source of the strains: clinical, veterinary, or environmental. The high diversity, especially amongst the Australian strains, suggests that S. aurantiacum may have originated within the Australian continent and was subsequently dispersed to other regions, as shown by the close phylogenetic relationships between some of the Australian sequence types and those found in other parts of the world. The MLST data are accessible at http://mlst.mycologylab.org. This is a joined publication of the ISHAM/ECMM working groups on “Scedosporium/Pseudallescheria Infections” and “Fungal Respiratory Infections in Cystic Fibrosis”.

Altered mental status is a major criterion for a diagnosis of encephalitis to be made with alteration in behavior, a key manifestation of altered mental status. We reviewed all evaluated cases identified by the Australian Childhood Encephalitis study between May 2013 and June 2018, to review the frequency and features of altered behavior (ALB). ALB was reported in >72% of cases of childhood encephalitis in all three major etiologic groups (infectious, immune-mediated, and unknown). The duration of ALB was >7 days in a minority, but significantly more frequent in immune-mediated compared with infectious encephalitis (27 and 10%, respectively, p < 0.01). ALB was most frequently characterized as irritability/agitation (47%), which predominated in children aged 1 year and most frequent in immune-mediated encephalitis. Hallucinations, paranoia, and aggression were all infrequent; suicidality/self-harm was not observed. ALB was reported in 20 of 21 cases of anti-N-methyl-d-aspartate receptor (anti-NMDAr), 19% for >7 days, and disorientation/confusion was the most frequent feature. Only one case was reported as presenting with “psychosis” and was diagnosed with anti-NMDAr encephalitis. Clinician-reported ALB is frequent but most often non-specific in childhood encephalitis. A longer duration of ALB is associated with an immune-mediated cause. More specific psychiatric symptoms (hallucinations, paranoia) are very infrequent. ALB is a hallmark of anti-NMDAr encephalitis, but psychosis is uncommon in contrast to the disorder in adults.

Objective To present Australia-wide data on paediatric COVID-19 and multisystem inflammatory syndromes to inform health service provision and vaccination prioritisation.Design Prospective, multicentre cohort study.Setting Eight tertiary paediatric hospitals across six Australian states and territories in an established research surveillance network—Paediatric Active Enhanced Disease (PAEDS).Participants All children aged

BackgroundThere is limited empiric evidence on the coverage of pneumococcal conjugate vaccines (PCVs) required to generate substantial indirect protection. We investigate the association between population PCV coverage and indirect protection against invasive pneumococcal disease (IPD) and pneumonia hospitalisations among undervaccinated Australian children.Methods and findingsBirth and vaccination records, IPD notifications, and hospitalisations were individually linked for children aged ConclusionsIn this study, we observed substantial indirect protection at lower levels of PCV coverage than previously described-challenging assumptions that high levels of PCV coverage (i.e., greater than 90%) are required. Understanding the association between PCV coverage and indirect protection is a priority since the control of vaccine-type pneumococcal disease is a prerequisite for reducing the number of PCV doses (from 3 to 2). Reduced dose schedules have the potential to substantially reduce program costs while maintaining vaccine impact.

Non-pharmaceutical interventions (NPIs) to reduce SARS-CoV-2 transmission disrupted respiratory virus seasonality. We examined the unusual return of human metapneumovirus (hMPV) in Western Australia following a period of absence in 2020. We analysed hMPV laboratory testing data from 1 January 2017 to 31 December 2021. Whole-genome sequencing of selected hMPV-positive samples was performed using a tiled-amplicon approach. Following an absence in spring 2020, an unusual hMPV surge was observed during the wet summer season in the tropical Northern region in late 2020. Following a six-month delay, an intense winter season occurred in the subtropical/temperate Southern and Metropolitan regions. Compared to 2017–2019, hMPV incidence in 2021 increased by 3-fold, with a greater than 4-fold increase in children aged 1–4 years. There was a collapse in hMPV diversity in 2020, with the emergence of a single subtype. NPIs contributed to an absent 2020 season and a clonal hMPV resurgence. The summer surge and delayed winter season suggest that prevailing temperature and humidity are keys determinant of hMPV transmission. The increased incidence in 2021 was linked to an expanded cohort of hMPV-naïve 1–4-year-old children and waning population immunity. Further intense and unusual respiratory virus seasons are expected as COVID-19 associated NPIs are removed.

The incidence of neonatal varicella has decreased dramatically since the introduction of the varicella vaccination. Although the varicella zoster virus is often associated with a mild infection, it may cause severe morbidity and mortality, particularly in the neonatal period and immunocompromised hosts. We report a case of neonatal varicella acquired from maternal zoster in a mother on biological immunosuppressive therapy. Following the diagnosis, the baby improved on antiviral therapy without any neurological sequelae. This case highlights the limited published data on neonatal varicella following herpes zoster reactivation to inform practice. This includes the role of varicella zoster immunoglobulin in neonates exposed to maternal zoster, the degree of trans-placental immunity and optimum antiviral dosing and duration.

Social learning, where information is acquired from others, is taxonomically widespread. There is growing evidence that animals selectively employ ‘social learning strategies', which determine e.g. when to copy others instead of learning asocially and whom to copy. Furthermore, once animals have acquired new information, e.g. regarding profitable resources, it is beneficial for them to commit it to long-term memory (LTM), especially if it allows access to profitable resources in the future. Research into social learning strategies and LTM has covered a wide range of taxa. However, otters (subfamily Lutrinae), popular in zoos due to their social nature and playfulness, remained neglected until a recent study provided evidence of social learning in captive smooth-coated otters (Lutrogale perspicillata), but not in Asian short-clawed otters (Aonyx cinereus). We investigated Asian short-clawed otters' learning strategies and LTM performance in a foraging context. We presented novel extractive foraging tasks twice to captive family groups and used network-based diffusion analysis to provide evidence of a capacity for social learning and LTM in this species. A major cause of wild Asian short-clawed otter declines is prey scarcity. Furthering our understanding of how they learn about and remember novel food sources could inform key conservation strategies.

Abstract Background Staphylococcus aureus bacteraemia (SAB) causes considerable morbidity and mortality in children. Despite this, its epidemiology and risk factors are poorly understood, with minimal paediatric clinical trial data available to guide clinicians in management. We conducted a pilot study to characterise SAB and validate a severity classification for use in future clinical trials. Methods Patients with SAB were prospectively identified at Princess Margaret Hospital for Children (Perth, Western Australia) from May 2011 to December 2013. Retrospective data were collected from clinical and laboratory records. Cases were classified based on a priori defined criteria as simple (single or contiguous, peripheral site focus) or complex (multi-site, deep tissue, no focus or sepsis) and tested against risk factors and markers of severity of infection. Results There were 49 cases of SAB (median age 7.7 years), with classification as simple (n = 30, 61%) and complex (n = 19, 39%) respectively. There were no deaths or relapses in our cohort. Only 10% of isolates were methicillin resistant S. aureus (MRSA), and none of these were healthcare-associated. Age, gender, Indigenous status, MRSA and healthcare-associated infections were not predictive of complex infection. Pre-existing malignancy was a risk factor for complex infection (p = 0.02). Complex infections were associated with a higher median maximum C reactive protein (216 mg/L vs 50 mg/L, p =

Aminoglycosides are commonly prescribed to children with febrile neutropenia (FN) but their impact on clinical outcomes is uncertain and extent of guideline compliance is unknown. We aimed to review aminoglycoside prescription and additional antibiotic prescribing, guideline compliance and outcomes for children with FN. We analysed data from the Australian Predicting Infectious ComplicatioNs in Children with Cancer (PICNICC) prospective multicentre cohort study, in children

Introduction Invasive meningococcal disease (IMD) primarily causes disease in young children and adolescents and can cause long-term disability. Many countries are considering implementation of meningococcal B and/or meningococcal ACWY vaccines to control meningococcal disease. Estimating the cost-effectiveness of meningococcal vaccine programme is hampered due to a lack of good quality costing and burden of disease data. This study aims to address this evidence gap by assessing the clinical, physical, neurocognitive, economic and societal impact of IMD on adolescents and young adults.Methods and analysis A case–control study of 64 participants with confirmed IMD (15–24 years 11 months at time of disease) and 64 control participants (17–34 years 11 months) will be conducted in Australia from 2016 to 2020. All participants will undergo a neurocognitive assessment, full medical examination, pure tone audiometry assessment and complete quality of life and behavioural questionnaires. Meningococcal cases will be assessed 2–10 years posthospitalisation and a subset of cases will be interviewed to explore in depth their experiences of IMD and its impact on their life. Primary outcome measures include general intellectual functioning from the Wechsler Adult Intelligence Scale and overall quality of life from the Health Utilities Index. Secondary outcome measures include academic achievement, executive functioning, behaviour, hearing, psychological and physical functioning. Outcome measures will be compared between cases and controls using independent t-tests or ORs, or if any significant confounders are identified, adjusted analyses (analysis of covariance or adjusted ORs) will be conducted. Thematic analysis will be used to analyse transcribed interviews and a costing model will be used to project lifetime costs.Ethics and dissemination The Adolescent MENingococcal Disease (AMEND) study has been approved by the Human Research Ethics Committee of the Women’s and Children’s Health Network (HREC/14/WCHN/024). The results will be disseminated via peer-reviewed publications, conference presentations, study participants, and meningococcal and meningitis foundations.Trial registration number NCT03798574.

Objectives Acute respiratory infections (ARIs) are a global cause of childhood morbidity. We compared temporal trends and socioeconomic disparities for ARI hospitalisations in young children across Western Australia, England and Scotland.Design Retrospective population-based cohort studies using linked birth, death and hospitalisation data.Setting and participants Population birth cohorts spanning 2000–2012 (Western Australia and Scotland) and 2003–2012 (England).Outcome measures ARI hospitalisations in infants (

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IntroductionOtitis media (OM) is one of the most common infectious diseases affecting children globally and the most common reason for antibiotic prescription and paediatric surgery. Australian Aboriginal children have higher rates of OM than non-Aboriginal children; however, there are no data comparing OM hospitalization rates between them at the population level. We report temporal trends for OM hospitalizations and in-hospital tympanostomy tube insertion (TTI) in a cohort of 469,589 Western Australian children born between 1996 and 2012.Materials and methodsWe used the International Classification of Diseases codes version 10 to identify hospitalizations for OM or TTI recorded as a surgical procedure. Using age-specific population denominators, we calculated hospitalization rates per 1,000 child-years by age, year and level of socio-economic deprivation.ResultsThere were 534,674 hospitalizations among 221,588 children hospitalized at least once before age 15 years. Aboriginal children had higher hospitalization rates for OM than non-Aboriginal children (23.3/1,000 [95% Confidence Interval (CI) 22.8,24.0] vs 2.4/1,000 [95% CI 2.3,2.4] child-years) with no change in disparity over time. Conversely non-Aboriginal children had higher rates of TTI than Aboriginal children (13.5 [95% CI 13.2,13.8] vs 10.1 [95% CI 8.9,11.4]). Children from lower socio-economic backgrounds had higher OM hospitalization rates than those from higher socio-economic backgrounds, although for Aboriginal children hospitalization rates were not statistically different across all levels of socio-economic disadvantage. Hospitalizations for TTI among non-Aboriginal children were more common among those from higher socio-economic backgrounds. This was also true for Aboriginal children; however, the difference was not statistically significant. There was a decline in OM hospitalization rates between 1998 and 2005 and remained stable thereafter.ConclusionAboriginal children and children from lower socio-economic backgrounds were over-represented with OM-related hospitalizations but had fewer TTIs. Despite a decrease in OM and TTI hospitalization rates during the first half of the study for all groups, the disparity between Aboriginal and non-Aboriginal children and between those of differing socioeconomic deprivation remained.

Introduction Several countries have developed national immunisation registers, but only the Nordic countries have 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 national person identifier, but most countries, including Australia, don’t have such an identifier to enable this type of linkage. Objectives To describe the process for assembling a linked study cohort that will enable the conduct of population-based studies related to immunisation and immunisation policy. Methods National death and immunisation databases along with state health data (notifications of vaccine preventable diseases, perinatal data, hospital admissions and emergency department presentations) up until December 2013 were probabilistically linked (using demographic details) for children born between 1996 and 2012 in two states: Western Australia and New South Wales (42% of Australia’s population, combined). Results After exclusions there were 1.95 million children in the study cohort (live born children with both a birth and perinatal record which represents 97.5% of all live births in the state perinatal data collections - our source population) and 18.0 million person years of follow up (mean: 9.2 years per child). The characteristics of children in the cohort were generally similar to those only included in state perinatal databases and outcome measures were in keeping with expected figures from unlinked data sources. However, the lack of a dynamic national population register meant immigrants could not be included. Conclusions We have been able to develop a similarly comprehensive system to the Nordic countries based on probabilistic linkage methods. Our experience should provide encouragement to other countries with national immunisation registers looking to establish similar systems.

ABSTRACT Objectives Acute lower respiratory infections (ALRI) such as bronchiolitis, pneumonia and influenza are a common cause of childhood morbidity. The relative importance of individual respiratory viruses associated with these infections may fluctuate in different populations. Knowledge of the aetiology of ALRI is important so that preventive strategies, such as vaccination, may be targeted appropriately. We sought to describe the virus-specific burden of ALRI in children born in Western Australia (WA). Approach We identified a birth cohort of children born in WA from 1996 to 2012. ALRI-coded hospital admissions and routine laboratory data regarding the detection of respiratory viruses pertaining to these children were extracted and linked through the WA Data Linkage Unit. Hospitalisation and laboratory data were restricted to Jan 2000 to Jun 2013 as laboratory data were only available for this period. Repeat hospital admissions for ALRI within 14 days of each other were collapsed into the same episode of infection. Virus detection was defined as detection via culture, immunofluorescence or molecular methods from a respiratory sample 48 hours pre- or post-hospitalisation. We estimated the proportion of ALRI episodes in children aged up to 17 years with a laboratory test recorded and identified the viruses detected. Using person-time-at-risk as the denominator, we calculated the virus-specific rates of ALRI in 2000-2012 in the birth cohort. Results Of 469,589 children born 1996-2012, 7.0% were admitted to hospital at least once for ALRI between Jan 2000 and Jun 2013. Bronchiolitis and pneumonia were the most common diagnoses, collectively accounting for 73.3% (n=32,815) of all ALRI episodes. 45.4% of ALRI episodes (n=20,323) in children aged 0-17 years linked to a laboratory test record. Of those with a laboratory record, 60.0% tested positive for one or more viruses, most commonly respiratory syncytial virus (RSV; n=7671). Of those with at least 1 virus detected, 4.7% had 2 or more viruses detected, with RSV-adenovirus being the most common viral pair. Among children aged under 5 years, rates of virus-related ALRI hospitalisation were highest in children aged 1-2 months (37.2 per 1000 child-years), corresponding to the peak in RSV-related hospitalisations (30.6 per 1000 child-years). By contrast, rates of adenovirus-related hospitalisations were highest in children aged 6-11 months (1.7 per 1000 child-years). Conclusion This study demonstrates the power of using linked data to assess the virus-specific burden of ALRI in a population of children. Future work will focus on viral-viral coinfection and its impact on clinical outcomes.