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Background Antimicrobial resistance is increasing globally, largely due to high rates of antibiotic use and misuse. Factors that influence frequent antibiotic use in children are poorly understood. Objectives This study describes rates of antibiotic use in Australian children and investigates parental factors including knowledge, attitudes and behaviours that influence antibiotic use. Methods An online questionnaire relating to antibiotic use was administered as part of the Royal Children’s Hospital National Child Health Poll to a randomly recruited nationwide sample of parents or guardians of children aged 0–17 years in Australia. Data on antibiotic use in children and parental knowledge of appropriate indications for antibiotics and behaviours were collected. Standard binary logistic regression was used to assess associations between parent demographics and behaviour with antibiotic administration. Results The survey was completed by 2157 parents (64% completion rate), of which 1131 (52%) reported having given oral antibiotics to one or more of their children in the preceding 12 months. Of the 3971 children represented overall, 1719 (43%) had received at least one course of antibiotics. The average number of courses per child was 0.86 overall and 1.96 courses per child among those with reported antibiotic use. Notably, 194/1131 (17%) parents reported giving antibiotics to their child without a prescription. Poor parental knowledge of antibiotic indications was associated with antibiotic use. Conclusions Reducing excessive use of antibiotics in children is necessary in the global strategy for preventing antimicrobial resistance. This study identified areas for public health interventions to educate parents and increase regulation of access to antibiotics.

Background As of mid-2021, Australia’s only nationwide coronavirus disease 2019 (COVID-19) epidemic occurred in the first 6 months of the pandemic. Subsequently, there has been limited transmission in most states and territories. Understanding community spread during the first wave was hampered by initial limitations on testing and surveillance. To characterize the prevalence of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2)-specific antibody seroprevalence generated during this time, we undertook Australia’s largest national SARS-CoV-2 serosurvey. Methods Between June 19 and August 6, 2020, residual specimens were sampled from people undergoing general pathology testing (all ages), women attending antenatal screening (20–39 years), and blood donors (20–69 years) based on the Australian population’s age and geographic distributions. Specimens were tested by Wantai total SARS-CoV-2-antibody assay. Seroprevalence estimates adjusted for test performance were produced. The SARS-CoV-2 antibody-positive specimens were characterized with microneutralization assays. Results Of 11 317 specimens (5132 general pathology; 2972 antenatal; 3213 blood-donors), 71 were positive for SARS-CoV-2-specific antibodies. Seroprevalence estimates were 0.47% (95% credible interval [CrI], 0.04%–0.89%), 0.25% (CrI, 0.03%–0.54%), and 0.23% (CrI, 0.04%–0.54%), respectively. No seropositive specimens had neutralizing antibodies. Conclusions Australia’s seroprevalence was extremely low (

Focus of Presentation Utilising data from multiple cohorts to address causal questions in health research has become increasingly widespread due to a number of advantages. These include improved precision of estimates, in particular to investigate effect heterogeneity as well as rare events and exposures, and the ability to examine the replicability of findings. However, undertaking causal inference in multi-cohort studies also faces several challenges, which makes clear causal thinking even more important than in single-cohort studies. We propose the use of the “target trial” framework for the conduct of causal inference in multi-cohort studies. Findings Using two case studies, the first considering the effect of maternal mental health on emotional reactivity and the second examining the influence of exposure to adversity on inflammatory outcomes in childhood, we describe and demonstrate how the target trial approach enables clear definition of the target estimand and systematic consideration of sources of bias. Considering the target trial as the reference point allows the identification of potential biases within each study, so that analysis can be planned to reduce them. Furthermore, the interpretation of findings is assisted by an understanding of the unavoidable biases that may be compounded when pooling data from multiple cohorts, or that may explain discrepant findings across cohorts. Conclusions/Implications Use of the target trial framework in multi-cohort studies helps strengthen causal inferences through improved analysis design and clarity in the interpretation of findings. Key messages The target trial framework, already well-established for casual inference in single-cohort studies, is recommended for the conduct of causal inference in multi-cohort studies.

Background Inflammation is one of key mechanisms linking childhood experiences to later chronic disease risk. Childhood adversity is associated with inflammation, but little is known about positive experiences. We examine how adverse and positive experiences are associated with inflammatory markers in late childhood, and whether they have an interaction effect. Methods Data sources: Longitudinal Study of Australian Children (LSAC; N = 1237) and Avon Longitudinal Study of Parents and Children (ALSPAC; N = 3488). Exposures: Adverse and positive experiences assessed from 0 to 11 (LSAC) and 0-14 years (ALSPAC). Adversity indicators included parent legal problems, family violence, mental illness, substance abuse, harsh parenting, parental divorce, neighbourhood violence, family member death, and bullying victimization. Positive experiences included positive parenting practice, trusting and supportive relationships, supportive neighbourhood and home learning environments, social engagement and enjoyment. Outcomes: Inflammation quantified by high-sensitivity C-reactive protein (hsCRP) and glycoprotein acetyls (GlycA). Analyses: Linear regression was used to estimate relative change in inflammatory markers, adjusted for sociodemographics. Outcomes were log-transformed. Results Exposure to adversity was associated with higher levels of inflammation (e.g., CRP: β = 8.8%, 95% CI= -16.5% to 34.2% in LSAC), whereas exposure to positive experiences was associated with lower levels (e.g., CRP: β=-18.9%, 95% CI= -45.8% to 7.9% in LSAC), after adjusting for sociodemographics. There was no interaction effect of adverse and positive experiences on inflammation. Conclusions Adverse and positive experiences have independent and small effects on children’s inflammation across two cohorts. Key messages Positive experiences are critical to inform interventions to improve inflammatory outcomes for children who face adversity.