Assessing the effects of SARS-CoV-2 vaccination on the risk of household transmission during delta variant circulation: a population-based data linkage cohort study.

Background: Data on SARS-CoV-2 vaccine effectiveness to reduce transmission of infection in household settings are limited. We examined the effects of SARS-CoV-2 vaccines on Delta variant transmission within households in an infection-naïve population. Methods: This was a population-based data linkage cohort study in the Greater Sydney Metropolitan Area, New South Wales, Australia based on cases observed in June-November 2021. In households with ≥1 confirmed COVID-19 case, we calculated adjusted odds ratios (aOR) and 95% Confidence Intervals (95% CI) for the risk of SARS-CoV-2 transmission, by vaccination status (unvaccinated, partially vaccinated, fully vaccinated, or waning) and type of vaccines (mRNA or vector-based) received by both index cases and household contacts. Findings: In 20,651 households with a single index case, 18,542 of 72,768 (25%) household contacts tested PCR-positive ≤14 days after their respective index case. Household contacts with partial, full, or waning mRNA vaccination had aORs of 0.46 (95% CI 0.40-0.52), 0.36 (95% CI 0.32-0.41) and 0.64 (95% CI 0.51-0.80) compared to unvaccinated contacts, while for vector vaccines the corresponding aORs were 0.77 (95% CI 0.67-0.89), 0.65 (95% CI 0.55-0.76), and 0.64 (95% CI 0.39-1.05). Full mRNA-vaccination in index cases compared to non-vaccination was associated with aORs between 0.09 and 0.21 depending on the vaccination status of household contacts. Interpretation: Full vaccination of household contacts reduced the odds to acquire infection with the SARS-CoV-2 Delta variant in household settings by two thirds for mRNA vaccines and by one third for vector vaccines. For index cases, being fully vaccinated with an mRNA vaccine reduced the odds of onwards transmission by four-fifths compared to unvaccinated index cases. Full vaccination offered stronger protection than partial vaccination, particularly for mRNA vaccines, but with reduced effects when the last vaccination preceded exposure by ≥3 months. Funding: New South Wales Ministry of Health.

Relative effectiveness of COVID-19 vaccination with 3 compared to 2 doses against SARS-CoV-2 B.1.1.529 (Omicron) among an Australian population with low prior rates of SARS-CoV-2 infection.

BACKGROUND: We estimate effectiveness of 3 versus 2 vaccine doses against SARS-CoV-2 B.1.1.529 Omicron in a mostly infection-naiive but highly vaccinated Australian population. METHODS: Cohort study of adults aged 40+ years resident in Sydney followed from 1 January 2022 for SARS-CoV-2 infection and COVID-19 hospitalisation or death using linked immunisation, disease notification and hospitalisation registers. Adjusted hazard ratios (aHR) and corresponding relative vaccine effectiveness (rVE) were estimated comparing 3 to 2 vaccine dose recipients by time since dose receipt, vaccine brand, and prior infection. Absolute risk reductions and numbers needed to boost by age groups were calculated. RESULTS: 2,053,123 infection-naiive individuals (mean age 59 years) were followed for 327,272 person-years for infection and 224,269 person-years for severe outcomes (hospitalisation/death). There were 175,849 infections and 4113 hospitalisations/deaths. Compared to individuals receiving dose 2 within the last 3 months, rVE in dose 3 recipients was 7% (95% CI 5-9%) against infection and 65% (95%CI 61-69%) against hospitalisation/death. Almost all dose 3 recipients had an mRNA vaccine; there was little difference in dose 3 rVE by primary course vaccine brand (ChAdOx1 versus BNT162b2). Over the 6-week follow-up, we estimated one hospitalisation/death was avoided for every 192 adults aged ≥70 years boosted with dose 3 in the infection-naiive cohort. The aHR for hospitalisation/death from Omicron was 0.12 (95 %CI 0.07-0.23) for 2-dose recipients with a prior Delta infection compared with 2-dose recipients with no prior infection. CONCLUSIONS: Receipt of a third COVID-19 vaccine dose in adults aged 40 years and above significantly reduced hospitalisations and deaths from SARS-CoV-2 Omicron infections in a primarily infection-naiive population.

Treatment of opioid dependence with depot buprenorphine (CAM2038) in custodial settings.

BACKGROUND AND AIMS: Opioid agonist treatment is effective but resource intensive to administer safely in custodial settings, leading to significant under-treatment of opioid dependence in these settings world-wide. This study assessed the safety of subcutaneous slow-release depot buprenorphine in custody. DESIGN: Open-label, non-randomized trial. SETTING: Correctional centres in New South Wales, Australia. PARTICIPANTS: Sixty-seven men and women, aged ≥ 18 years of various security classifications with a diagnosis of moderate to severe DSM-5 opioid use disorder currently serving a custodial sentence of ≥ 6 months were recruited between November 2018 and July 2019. Patients not in opioid agonist treatment at recruitment commenced depot buprenorphine; patients already stable on oral methadone treatment were recruited to the comparison arm. INTERVENTION AND COMPARATOR: Depot buprenorphine (CAM2038 weekly for 4 weeks then monthly) and daily oral methadone. MEASUREMENTS: Safety was assessed by adverse event (AE) monitoring and physical examinations at every visit. Participants were administered a survey assessing self-reported diversion and substance use at baseline and weeks 4 and 16. FINDINGS: Retention in depot buprenorphine treatment was 92.3%. Ninety-four per cent of patients reported at least one adverse event, typically mild and transient. No diversion was identified. The prevalence of self-reported non-prescribed opioid use among depot buprenorphine patients decreased significantly between baseline (97%) and week 16 (12%, odds ratio = 0.0035, 95% confidence interval = 0.0007-0.018, P < 0.0001). CONCLUSIONS: This first study of depot buprenorphine in custodial settings showed treatment retention and outcomes comparable to those observed in community settings and for other opioid agonist treatment used in custodial settings, without increased risk of diversion.

A quantitative analysis of MDMA seized at New South Wales music festivals over the 2019/2020 season: Form, purity, dose and adulterants.

INTRODUCTION: This research aims to understand the content and nature, and to explore the harm potential, of suspected 3,4-methylenedioxymethamphetamine (MDMA) substances circulating at music festivals in New South Wales. METHODS: Across 19 music festivals held between October 2019 and March 2020, 302 substances detected and suspected by police to contain MDMA were selected for quantitative analysis. RESULTS: Five percent of substances contained a drug other than MDMA (n = 13) or no drug (n = 2). The remaining 95.0% (n = 287) contained MDMA. Of this sub-sample, capsule was the commonest form (83.3%), followed by tablet (7.7%), crystal (6.3%) and powder (2.8%). The median MDMA base-purity of non-tablet forms ranged between 73.5% and 75.0%. The median MDMA base-dose per tablet (116 mg) was higher than per capsule (68 mg). The dose range varied substantially for capsules (14-146 mg) and tablets (24-201 mg). A higher dose (130 mg or greater) was found in 3.5% of MDMA tablets or capsules. Adulterants were identified in 14.1% of MDMA substances but only 1.6% contained a psychoactive adulterant and none presented as dangerous due to their nature or low concentration. DISCUSSION AND CONCLUSIONS: Dangerous MDMA adulterants or new psychoactive substances in tablet, capsule, powder or crystal forms (whether misrepresented as MDMA or not) were unlikely to be in circulation during the study period. Harm reduction messaging should inform that a key risk-factor for MDMA-related harm is the high and wide variation of purity and dose across forms. Market changes may have occurred since COVID-19, but continued monitoring will ensure messaging remains current.

NSW Health COVID-19 Emergency Response Priority Research program: a case study of rapid translation of research into health decision making.

OBJECTIVES: The NSW Health COVID-19 Research Program was established in April 2020 to contribute to minimising the health, social and economic impacts of the coronavirus disease 2019 (COVID-19) pandemic in New South Wales (NSW). This paper describes the establishment and implemention of one element of the Program, the Emergency Response Priority Research (Emergency Response) workstream, which is focused on the rapid creation of evidence to support urgent operational work for the public health management of COVID-19 in NSW. METHODS: Narrative description. RESULTS: As at June 2021, nine Emergency Response projects had been funded. Mechanisms used to expedite projects included: embedding academic researchers in NSW Health to work directly with routinely collected NSW Health data; adapting existing research projects to include a COVID-19 component; leveraging established research partnerships to conduct rapid pilots; and directly commissioning urgent projects with experienced and trusted local researchers. LESSONS LEARNT: Evidence from Emergency Response projects has contributed directly to informing the NSW public health response. For example, findings from a study of COVID-19 transmission in schools and childcare settings in the early stages of the pandemic informed decisions around the resumption of on-campus education in 2020 and helped shape policy around higher risk activities to help reduce transmission in education settings. Similarly, findings from a project to validate methods for identifying SARS-CoV-2 virus fragments in wastewater were subsequently incorporated into the NSW Sewage Surveillance Program, which continues to provide NSW Health with information to support targeted messaging and testing. The approach to establishing and implementing the Emergency Response workstream highlights the importance of continuing to ensure a well-trained public health research community and actively supporting a collaborative research sector.

Combining structured and unstructured data in EMRs to create clinically-defined EMR-derived cohorts.

BACKGROUND: There have been few studies describing how production EMR systems can be systematically queried to identify clinically-defined populations and limited studies utilising free-text in this process. The aim of this study is to provide a generalisable methodology for constructing clinically-defined EMR-derived patient cohorts using structured and unstructured data in EMRs. METHODS: Patients with possible acute coronary syndrome (ACS) were used as an exemplar. Cardiologists defined clinical criteria for patients presenting with possible ACS. These were mapped to data tables within the production EMR system creating seven inclusion criteria comprised of structured data fields (orders and investigations, procedures, scanned electrocardiogram (ECG) images, and diagnostic codes) and unstructured clinical documentation. Data were extracted from two local health districts (LHD) in Sydney, Australia. Outcome measures included examination of the relative contribution of individual inclusion criteria to the identification of eligible encounters, comparisons between inclusion criterion and evaluation of consistency of data extracts across years and LHDs. RESULTS: Among 802,742 encounters in a 5 year dataset (1/1/13-30/12/17), the presence of an ECG image (54.8% of encounters) and symptoms and keywords in clinical documentation (41.4-64.0%) were used most often to identify presentations of possible ACS. Orders and investigations (27.3%) and procedures (1.4%), were less often present for identified presentations. Relevant ICD-10/SNOMED CT codes were present for 3.7% of identified encounters. Similar trends were seen when the two LHDs were examined separately, and across years. CONCLUSIONS: Clinically-defined EMR-derived cohorts combining structured and unstructured data during cohort identification is a necessary prerequisite for critical validation work required for development of real-time clinical decision support and learning health systems.

Toxicological analysis of serious drug-related harm among electronic dance music festival attendees in New South Wales, Australia: A consecutive case series.

BACKGROUND: A substantial increase in drug-related harm was observed during the 2018-2019 music festival season in New South Wales, Australia, including the deaths of five young people. As part of a rapid public health response, the New South Wales Ministry of Health referred samples from patients with suspected severe drug-related illness for forensic toxicological testing to identify the type and concentration of substances associated with the presentations. METHODS: Cases were identified through a variety of active and passive surveillance systems, and selected consecutively based on indicators of clinical severity. Comprehensive toxicology testing of blood and urine samples was expedited for all cases. Demographic and clinical characteristics were collated, together with quantitative toxicology results. Results were analysed using descriptive statistics. RESULTS: Forty cases from eleven different music festivals were included. The majority of cases (80.0%) were aged 25 years and under. There were five fatalities, and 62.5% of cases were admitted to intensive care units. MDMA was the most frequent substance, detected in 87.5% of cases. In 82.9% of cases with MDMA, blood concentrations were above thresholds that have been associated with toxicity. Multiple substances were detected in 60.0% of cases. Novel psychoactive substances were not detected. CONCLUSIONS: Our findings strongly suggest that MDMA-related toxicity was a major factor in the severity of the clinical presentations among these cases. Other substances may have enhanced MDMA toxicity but appear unlikely to have caused severe toxicity in isolation. These findings have important implications for harm reduction strategies targeted to music festival settings.

Cardiac procedures in ST-segment-elevation myocardial infarction - the influence of age, geography and Aboriginality.

BACKGROUND: Timely restoration of bloodflow acute ST-segment elevation myocardial infarction (STEMI) reduces myocardial damage and improves prognosis. The objective of this study was describe the association of demographic factors with hospitalisation rates for STEMI and time to angiography, Percutaneous Coronary Intervention (PCI) and Coronary Artery Bypass Graft (CABG) in New South Wales (NSW) and the Australian Capital Territory (ACT), Australia. METHODS: This was an observational cohort study using linked population health data. We used linked records of NSW and the ACT hospitalisations and the Australian Government Medicare Benefits Schedule (MBS) for persons aged 35 and over hospitalised with STEMI in the period 1 July 2010 to 30 June 2014. Survival analysis was used to determine the time between STEMI admission and angiography, PCI and CABG, with a competing risk of death without cardiac procedure. RESULTS: Of 13,117 STEMI hospitalisations, 71% were among males; 55% were 65-plus years; 64% lived in major cities, and 2.6% were Aboriginal people. STEMI hospitalisation occurred at a younger age in males than females. Angiography and PCI rates decreased with age: angiography 69% vs 42% and PCI 60% vs 34% on day 0 for ages 35-44 and 75-plus respectively. Lower angiography and PCI rates and higher CABG rates were observed outside major cities. Aboriginal people with STEMI were younger and more likely to live outside a major city. Angiography, PCI and CABG rates were similar for Aboriginal and non-Aboriginal people of the same age and remoteness area. CONCLUSIONS: There is a need to improve access to definitive revascularisation for STEMI among appropriately selected older patients and in regional areas. Aboriginal people with STEMI, as a population, are disproportionately affected by access to definitive revascularisation outside major cities. Improving access to timely definitive revascularisation in regional areas may assist in closing the gap in cardiovascular outcomes between Aboriginal and non-Aboriginal people.

How can health services strengthen support for children affected by overweight and obesity, and their families?

More than a quarter of Australian children are above a healthy weight (overweight or obese) and risk significant immediate and future health harms. While childhood overweight and obesity is a complex problem requiring multifaceted solutions, identifying children at risk and preventing these health harms should be a part of good clinical care in all health services. Effective secondary and tertiary prevention is feasible. This paper argues that health services can use serial growth assessment to routinely identify and manage children who are above a healthy weight, just as we might routinely identify and manage hypertension in older patients. We highlight the evidence for the acceptability and effectiveness of family-focused clinical intervention for weight management in children. We also outline system-level changes that health services should consider to enable and support routine clinical identification and management of affected children and their families.

Alcopops, taxation and harm: a segmented time series analysis of emergency department presentations.

BACKGROUND: In Australia, a Goods and Services Tax (GST) introduced in 2000 led to a decline in the price of ready-to-drink (RTD) beverages relative to other alcohol products. The 2008 RTD ("alcopops") tax increased RTD prices. The objective of this study was to estimate the change in incidence of Emergency Department (ED) presentations for acute alcohol problems associated with each tax. METHODS: Segmented regression analyses were performed on age and sex-specific time series of monthly presentation rates for acute alcohol problems to 39 hospital emergency departments across New South Wales, Australia over 15 years, 1997 to 2011. Indicator variables represented the introduction of each tax. Retail liquor turnover controlled for large-scale economic factors such as the global financial crisis that may have influenced demand. Under-age (15-17 years) and legal age (18 years and over) drinkers were included. RESULTS: The GST was associated with a statistically significant increase in ED presentations for acute alcohol problems among 18-24 year old females (0 · 14/100,000/month, 95% CI 0 · 05-0 · 22). The subsequent alcopops tax was associated with a statistically significant decrease in males 15-50 years, and females 15-65 years, particularly in 18-24 year old females (-0 · 37/100,000/month, 95% CI -0 · 45 to -0 · 29). An increase in retail turnover of liquor was positively and statistically significantly associated with ED presentations for acute alcohol problems across all age and sex strata. CONCLUSIONS: Reduced tax on RTDs was associated with increasing ED presentations for acute alcohol problems among young women. The alcopops tax was associated with declining presentations in young to middle-aged persons of both sexes, including under-age drinkers.

The association between the density of retail tobacco outlets, individual smoking status, neighbourhood socioeconomic status and school locations in New South Wales, Australia.

AIM: We explored the association between the density of tobacco outlets and neighbourhood socioeconomic status, and between neighbourhood tobacco outlet density and individual smoking status. We also investigated the density of tobacco outlets around primary and secondary schools in New South Wales (NSW). METHODS: We calculated the mean density of retail tobacco outlets registered in NSW between 2009 and 2011, using kernel density estimation with an adaptive bandwidth. We used generalised ordered logistic regression model to explore the association between socioeconomic status and density of tobacco outlets. The association between neighbourhood tobacco outlet density and individuals' current smoking status was investigated using random-intercept generalised linear mixed models. We also calculated the median tobacco outlet density around NSW schools. RESULTS: More disadvantaged Census Collection Districts (CDs) were significantly more likely to have higher tobacco outlet densities. After adjusting for neighbourhood socioeconomic status and participants' age, sex, country of birth and Aboriginal status, neighbourhood mean tobacco outlet density was significantly and positively associated with individuals' smoking status. The median of tobacco outlet density around schools was significantly higher than the state median. CONCLUSION: Policymakers could consider exploring a range of strategies that target tobacco outlets in proximity to schools, in more disadvantaged neighbourhoods and in areas of existing high tobacco outlet density.

Testing-adjusted chlamydia notification trends in New South Wales, Australia, 2000 to 2010.

INTRODUCTION: Between 2005 and 2010, Australian notification rates for chlamydia infection increased by 64% from 203 to 333 per 100 000 population. Interpreting this trend is difficult without examining rates and local patterns of testing. We examined the effect of adjusting for local testing rates on chlamydia notification trends in New South Wales (NSW), Australia from 2000 to 2010. METHODS: We used testing data for NSW residents for Medicare Benefits Schedule items for chlamydia from 1 July 1999 to 30 June 2005 and 1 July 2007 to 30 June 2010. This data set excluded testing by public sector laboratories. We also obtained laboratory-confirmed genital chlamydia notifications in NSW residents for 1 July 1999 to 30 June 2010 and excluded notifications from public laboratories. We used negative binomial regression to assess trends in chlamydia notification rates by age and sex after adjusting for local government area (LGA)-level Medicare-funded testing rates, socioeconomic disadvantage, remoteness and Medicare provider density. RESULTS: Testing-adjusted rates of chlamydia notifications declined by 5.2% per annum (rate ratio [RR] = 0.95, 95% confidence interval (CI) = 0.93-0.96) for women overall, and 2.3% (RR = 0.98, 95% CI = 0.96-1.00) and 5.0% per annum (RR = 0.95, 95% CI = 0.93-0.98) for men in LGAs with moderate and high densities of Medicare providers, respectively. Notification rates remained stable for men in low Medicare provider density LGAs (RR = 1.01, 95% CI = 0.96-1.07). DISCUSSION: It is likely that increased testing for chlamydia has driven increases in chlamydia notification in NSW over the last decade. Notification data provide no evidence for a general increase in the prevalence of chlamydia in the NSW community for this period. Notification-based chlamydia surveillance should be routinely adjusted for local testing rates.

The health of Hunter Valley communities in proximity to coal mining and power generation, general practice data, 1998-2010.

AIM: An analysis of general practice data for rural communities in close proximity to coal mining and coal-fired power generation in the Hunter Valley region of NSW was conducted to identify unusual patterns of illness. METHODS: Bettering the Evaluation and Care of Health general practice consultation data from the Hunter Valley region for 1998-2010 were compared with data from all other rural NSW residents. RESULTS: There were no significantly higher rates of problems managed or medications prescribed for Hunter Valley region residents compared with the rest of rural NSW. Rates of respiratory problem management in the Hunter Valley region did not change significantly over time, while for all other rural NSW areas these rates significantly decreased. CONCLUSION: There was no evidence of significantly elevated health issues for residents in the Hunter Valley region of NSW. The diverging trend for respiratory problem management over time is worthy of further exploration.

Potential for the Australian and New Zealand paediatric intensive care registry to enhance acute flaccid paralysis surveillance in Australia: a data-linkage study.

BACKGROUND: Australia uses acute flaccid paralysis (AFP) surveillance to monitor its polio-free status. The World Health Organization criterion for a sensitive AFP surveillance system is the annual detection of at least one non-polio AFP case per 100,000 children aged less than 15 years, a target Australia has not consistently achieved. Children exhibiting AFP are likely to be hospitalised and may be admitted to an intensive care unit. This provides a potential opportunity for active AFP surveillance. METHODS: A data-linkage study for the period from 1 January 2005 to 31 December 2008 compared 165 non-polio AFP cases classified by the Polio Expert Panel with 880 acute neurological presentations potentially compatible with AFP documented in the Australian and New Zealand Paediatric Intensive Care (ANZPIC) Registry. RESULTS: Forty-two (25%) AFP cases classified by the Polio Expert Panel were matched to case records in the ANZPIC Registry. Of these, nineteen (45%) cases were classified as Guillain-Barré syndrome on both registries. Ten additional Guillain-Barré syndrome cases recorded in the ANZPIC Registry were not notified to the national AFP surveillance system. CONCLUSIONS: The identification of a further ten AFP cases supports inclusion of intensive care units in national AFP surveillance, particularly specialist paediatric intensive care units, to identify AFP cases that may not otherwise be reported to the national surveillance system.

Seroepidemiologic effects of influenza A(H1N1)pdm09 in Australia, New Zealand, and Singapore.

To estimate population attack rates of influenza A(H1N1)pdm2009 in the Southern Hemisphere during June-August 2009, we conducted several serologic studies. We pooled individual-level data from studies using hemagglutination inhibition assays performed in Australia, New Zealand, and Singapore. We determined seropositive proportions (titer ≥40) for each study region by age-group and sex in pre- and postpandemic phases, as defined by jurisdictional notification data. After exclusions, the pooled database consisted of, 4,414 prepandemic assays and 7,715 postpandemic assays. In the prepandemic phase, older age groups showed greater seropositive proportions, with age-standardized, community-based proportions ranging from 3.5% in Singapore to 11.9% in New Zealand. In the postpandemic phase, seropositive proportions ranged from 17.5% in Singapore to 30.8% in New Zealand, with highest proportions seen in school-aged children. Pregnancy and residential care were associated with lower postpandemic seropositivity, whereas Aboriginal and Torres Strait Islander Australians and Pacific Peoples of New Zealand had greater postpandemic seropositivity.

The impact of influenza A(H1N1)pdm09 compared with seasonal influenza on intensive care admissions in New South Wales, Australia, 2007 to 2010: a time series analysis.

BACKGROUND: In Australia, the 2009 epidemic of influenza A(H1N1)pdm09 resulted in increased admissions to intensive care. The annual contribution of influenza to use of intensive care is difficult to estimate, as many people with influenza present without a classic influenza syndrome and laboratory testing may not be performed. We used a population-based approach to estimate and compare the impact of recent epidemics of seasonal and pandemic influenza. METHODS: For 2007 to 2010, time series describing health outcomes in various population groups were prepared from a database of all intensive care unit (ICU) admissions in the state of New South Wales, Australia. The Serfling approach, a time series method, was used to estimate seasonal patterns in health outcomes in the absence of influenza epidemics. The contribution of influenza was estimated by subtracting expected seasonal use from observed use during each epidemic period. RESULTS: The estimated excess rate of influenza-associated respiratory ICU admissions per 100,000 inhabitants was more than three times higher in 2007 (2.6/100,000, 95% CI 2.0 to 3.1) than the pandemic year, 2009 (0.76/100,000, 95% CI 0.04 to 1.48). In 2009, the highest excess respiratory ICU admission rate was in 17 to 64 year olds (2.9/100,000, 95% CI 2.2 to 3.6), while in 2007, the highest excess rate was in those aged 65 years or older (9.5/100,000, 95% CI 6.2 to 12.8). In 2009, the excess rate was 17/100,000 (95% CI 14 to 20) in Aboriginal people and 14/100,000 (95% CI 13 to 16) in pregnant women. CONCLUSION: While influenza was diagnosed more frequently and peak use of intensive care was higher during the epidemic of pandemic influenza in 2009, overall excess admissions to intensive care for respiratory illness was much greater during the influenza season in 2007. Thus, the impact of seasonal influenza on intensive care use may have previously been under-recognised. In 2009, high ICU use among young to middle aged adults was offset by relatively low use among older adults, and Aboriginal people and pregnant women were substantially over-represented in ICUs. Greater emphasis on prevention of serious illness in Aboriginal people and pregnant women should be a priority in pandemic planning.

Prevalence of chronic hepatitis B in South Western Sydney: evaluation of the country of birth method using maternal seroprevalence data.

OBJECTIVE: To estimate the prevalence of hepatitis B infection and evaluate the country of birth (Census) method of describing hepatitis B distribution in an Australian health service with a large migrant population. METHODS: The prevalence of chronic hepatitis B in Sydney South West Area Health Service (SSWAHS, population 1.3 million) was estimated by applying the prevalence of hepatitis B surface antigen (HBsAg) in high or intermediate hepatitis B prevalence countries to SSWAHS residents from those countries, using 2006 Census data. The Australian hepatitis B prevalence (0.7%) was applied to the remainder. This method was validated using HBsAg seroprevalence in 42,274 women aged 15-44 years who delivered at SSWAHS public maternity hospitals during 2007 to 2009. RESULTS: The SSWAHS prevalence of HBsAg using the Census method was 2.0% for all ages and 2.3% for 15-44 year old women. The seroprevalence in 15-44 year old mothers was 1.8%. The adjusted population prevalence was 1.6%. The two methods produced broadly similar descriptions of relative hepatitis B burden by local government area and country of birth. CONCLUSION: The Census method overestimates the prevalence of hepatitis B infection by 30%, but produces similar patterns of hepatitis B burden across the area. Health services can estimate the prevalence and distribution of chronic hepatitis B using readily available data to focus delivery of prevention and treatment services.

Influenza A testing and detection in patients admitted through emergency departments in Sydney during winter 2009: implications for rational testing.

AIM: To examine factors associated with testing and detection of influenza A in patients admitted to hospital for acute care during the winter 2009 pandemic influenza outbreak. DESIGN, SETTING AND PARTICIPANTS: Retrospective observational study of patients who were tested for influenza A after being admitted to hospital through emergency departments of the Sydney South West Area Health Service from 15 June to 30 August 2009. MAIN OUTCOME MEASURES: The association of factors such as age, diagnosis at admission, hospital and week of admission with rates of testing and detection of influenza A. RESULTS: 17,681 patients were admitted through nine emergency departments; 1344 (7.6%) were tested for influenza A, of whom 356 (26.5%) tested positive for pandemic influenza. Testing rates were highest in 0-4-year-old children, in the peak period of the outbreak, and in patients presenting with a febrile or respiratory illness. Positive influenza test results were common across a range of diagnoses, but occurred most frequently in children aged 10-14 years (64.3%) and in patients with a diagnosis at admission of influenza-like illness (59.1%). Using multivariate logistic regression, patients with a diagnosis at admission of fever or a respiratory illness at admission were most likely to be tested (odds ratios [ORs], 15 [95% CI, 11-21] and 17 [95% CI, 15-19], respectively). These diagnoses were stronger predictors of influenza testing than the peak testing week (Week 4; OR, 7.0 [95% CI, 3.8-13]) or any age group. However, diagnosis at admission and age were significant but weak predictors of a positive test result, and the strongest predictor of a positive test result was the peak epidemic week (Week 3; OR, 120 [95% CI, 27-490]). CONCLUSION: The strongest predictor of a clinician's decision to test for influenza was the diagnosis at admission, but the strongest predictor of a positive test was the week of admission. A rational approach to influenza testing for patients who are admitted to hospital for acute care could include active tracking of influenza testing and detection rates, testing patients with a strong indication for antiviral treatment, and admitting only those who test negative to "clean" wards during the peak of an outbreak.

Influenza A (H1N1) 2009 antibodies in residents of New South Wales, Australia, after the first pandemic wave in the 2009 southern hemisphere winter.

BACKGROUND: The first wave of pandemic influenza A(H1N1)2009 (pH1N1) reached New South Wales (NSW), Australia in May 2009, and led to high rates of influenza-related hospital admission of infants and young to middle-aged adults, but no increase in influenza-related or all-cause mortality. METHODOLOGY/PRINCIPAL FINDINGS: To assess the population rate of pH1N1 infection in NSW residents, pH1N1-specific haemagglutination inhibition (HI) antibody prevalence was measured in specimens collected opportunistically before (2007-2008; 474 specimens) and after (August-September 2009; 1247 specimens) the 2009 winter, and before the introduction of the pH1N1 monovalent vaccine. Age- and geographically-weighted population changes in seroprevalence were calculated. HI antibodies against four recent seasonal influenza A viruses were measured to assess cross-reactions. Pre- and post-pandemic pH1N1 seroprevalences were 12.8%, and 28.4%, respectively, with an estimated overall infection rate of 15.6%. pH1N1 antibody prevalence increased significantly - 20.6% overall - in people born since 1944 (26.9% in those born between 1975 and 1997) but not in those born in or before 1944. People born before 1925 had a significantly higher pH1N1 seroprevalence than any other age-group, and against any seasonal influenza A virus. Sydney residents had a significantly greater change in prevalence of antibodies against pH1N1 than other NSW residents (19.3% vs 9.6%). CONCLUSIONS/SIGNIFICANCE: Based on increases in the pH1N1 antibody prevalence before and after the first pandemic wave, 16% of NSW residents were infected by pH1N1 in 2009; the highest infection rates (27%) were among adolescents and young adults. Past exposure to the antigenically similar influenza A/H1N1(1918) is the likely basis for a very high prevalence (49%) of prepandemic cross-reacting pH1N1 antibody and sparing from pH1N1 infection among people over 85 years. Unless pre-season vaccine uptake is high, there are likely to be at least moderate rates including some life-threatening cases of pH1N1 infection among young people during subsequent winters.