COVID-19 Vaccine Uptake by Infection Status in New South Wales, Australia.

Using linked public health data from Australia to measure uptake of COVID-19 vaccination by infection status, we found coverage considerably lower among infected than uninfected persons for all ages. Increasing uptake of scheduled doses, including among previously infected persons after the recommended postinfection delay, is needed to reduce COVID-19 illness rates.

Status epilepticus outcomes among vaccinated and unvaccinated children: A population-based study.

AIM: To determine the proportion of first status epilepticus (SE) cases that are vaccine-proximate (VP-) and compare clinical outcomes to non-vaccine-proximate (NVP-) cases. METHODS: Birth records for 1,440,807 Australian children born in 1998-2012, were probabilistically linked to hospitalizations, deaths, and vaccination history available to 2013. First SE coded hospitalizations were categorized as VP-SE or NVP-SE; clinical severity and post-SE vaccination coverage were compared. SE rates were calculated. RESULTS: Of 867 first SE cases (7.9 per 100,000 person-years), 31 (3.6%) were VP-SE; 16 followed dose-1 measles vaccine (1.2 SE per 100,000 doses). Compared with NVP-SE, VP-SE cases were younger (1.0 vs 2.6 years, P < 0.0001) and had longer hospitalizations (4 vs 3 days, P = 0.005). There was no difference in the proportion of VP-SE cases with a coinfection diagnosis compared to NVP-SE (25.8% vs 19.9%, P = 0.42). Controlling for age and history of hospitalization for a neurological condition, intensive care unit (ICU) admission had a stronger association with coinfection (aOR 2.52 (95%CI 1.78-3.57)) than having VP-SE (aOR 1.41 (0.66-3.01)). Groups had similar SE recurrence rates at 12-months (12.9% VP vs 16.9% NVP, P = 0.56) and reduced vaccine uptake following initial SE (from 93.5% to 56.3%). CONCLUSION: Proportionally few first SE cases were VP-SE, with higher ICU admission rates mostly explained by younger age and higher coinfection rates. Vaccination plans are needed to improve vaccine uptake following SE.

Levels of pneumococcal conjugate vaccine coverage and indirect protection against invasive pneumococcal disease and pneumonia hospitalisations in Australia: An observational study.

BACKGROUND: There 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 FINDINGS: Birth and vaccination records, IPD notifications, and hospitalisations were individually linked for children aged <5 years, born between 2001 and 2012 in 2 Australian states (New South Wales and Western Australia; 1.37 million children). Using Poisson regression models, we examined the association between PCV coverage, in small geographical units, and the incidence of (1) 7-valent PCV (PCV7)-type IPD; (2) all-cause pneumonia; and (3) pneumococcal and lobar pneumonia hospitalisation in undervaccinated children. Undervaccinated children received <2 doses of PCV at <12 months of age and no doses at ≥12 months of age. Potential confounding variables were selected for adjustment a priori with the assistance of a directed acyclic graph. There were strong inverse associations between PCV coverage and the incidence of PCV7-type IPD (adjusted incidence rate ratio [aIRR] 0.967, 95% confidence interval [CI] 0.958 to 0.975, p-value < 0.001), and pneumonia hospitalisations (all-cause pneumonia: aIRR 0.991 95% CI 0.990 to 0.994, p-value < 0.001) among undervaccinated children. Subgroup analyses for children <4 months old, urban, rural, and Indigenous populations showed similar trends, although effects were smaller for rural and Indigenous populations. Approximately 50% coverage of PCV7 among children <5 years of age was estimated to prevent up to 72.5% (95% CI 51.6 to 84.4) of PCV7-type IPD among undervaccinated children, while 90% coverage was estimated to prevent 95.2% (95% CI 89.4 to 97.8). The main limitations of this study include the potential for differential loss to follow-up, geographical misclassification of children (based on residential address at birth only), and unmeasured confounders. CONCLUSIONS: In 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.

Seroprevalence of hepatitis B antibodies among international and domestic university students.

Chronic hepatitis B prevalence is low in most Australian populations, with universal infant HBV vaccination introduced in 2000. Migrants from high prevalence countries are at risk of acquisition before arrival and non-immune adults are potentially at risk through skin penetrating procedures and sexual contact, particularly during international travel. The risk profile of young adult students, many from high prevalence countries, is inadequately understood. A cross-sectional online survey conducted among university students collected data on demographic, vaccination and travel characteristics and blood samples were tested for hepatitis B surface antibody (HBsAb) and hepatitis B core antibody (HBcAb). Analyses identified factors associated with HBsAb seroprevalence and self-reported vaccination. The serosurvey was completed by 804 students born between 1988 and 1993, with 613/804 (76.2%, 95% CI 73.2-79.1) self-reporting prior HBV vaccination. Overall, 526/804 (65.4%, 95% CI 62.0%-68.6%) students were seropositive to HBsAb, including 438/613 (71.5%, 95% CI 67.8-74.9) students self-reporting a prior HBV vaccine and 88/191 (46.1%, 95% CI 39.2-53.2) students self-reporting no prior HBV vaccine. Overall, 8/804 (1.0%, 95% CI 0.5%-2.0%) students were HBcAb positive, of whom 1/804 (0.1%, 95% CI 0.02%-0.7%) was currently infectious. The prevalence of chronic HBV infection was low. However, more than one in four students were susceptible to HBV and over-estimated their immunity. Future vaccination efforts should focus on domestic students born before the introduction of the infant program and all international students. Screening and vaccination of students, including through campus-based health services, are an opportunity to catch-up young adults prior to undertaking at-risk activities, including international travel.

Seroprevalence of SARS-CoV-2-specific antibodies in Sydney after the first epidemic wave of 2020.

OBJECTIVES: To estimate SARS-CoV-2-specific antibody seroprevalence after the first epidemic wave of coronavirus disease 2019 (COVID-19) in Sydney. SETTING, PARTICIPANTS: People of any age who had provided blood for testing at selected diagnostic pathology services (general pathology); pregnant women aged 20-39 years who had received routine antenatal screening; and Australian Red Cross Lifeblood plasmapheresis donors aged 20-69 years. DESIGN: Cross-sectional study; testing of de-identified residual blood specimens collected during 20 April - 2 June 2020. MAIN OUTCOME MEASURE: Estimated proportions of people seropositive for anti-SARS-CoV-2-specific IgG, adjusted for test sensitivity and specificity. RESULTS: Thirty-eight of 5339 specimens were IgG-positive (general pathology, 19 of 3231; antenatal screening, 7 of 560; plasmapheresis donors, 12 of 1548); there were no clear patterns by age group, sex, or location of residence. Adjusted estimated seroprevalence among people who had had general pathology blood tests (all ages) was 0.15% (95% credible interval [CrI], 0.04-0.41%), and 0.29% (95% CrI, 0.04-0.75%) for plasmapheresis donors (20-69 years). Among 20-39-year-old people, the age group common to all three collection groups, adjusted estimated seroprevalence was 0.24% (95% CrI, 0.04-0.80%) for the general pathology group, 0.79% (95% CrI, 0.04-1.88%) for the antenatal screening group, and 0.69% (95% CrI, 0.04-1.59%) for plasmapheresis donors. CONCLUSIONS: Estimated SARS-CoV-2 seroprevalence was below 1%, indicating that community transmission was low during the first COVID-19 epidemic wave in Sydney. These findings suggest that early control of the spread of COVID-19 was successful, but efforts to reduce further transmission remain important.

Childhood vaccination coverage in Australia: an equity perspective.

BACKGROUND: This study describes trends in social inequities in first dose measles-mumps-rubella (MMR1) vaccination coverage in Western Australia (WA) and New South Wales (NSW). Using probabilistically-linked administrative data for 1.2 million children born between 2002 and 2011, we compared levels and trends in MMR1 vaccination coverage measured at age 24 months by maternal country of birth, Aboriginal status, maternal age at delivery, socio-economic status, and remoteness in two states. RESULTS: Vaccination coverage was 3-4% points lower among children of mothers who gave birth before the age of 20 years, mothers born overseas, mothers with an Aboriginal background, and parents with a low socio-economic status compared to children that did not belong to these social groups. In both states, between 2007 and 2011 there was a decline of 2.1% points in MMR1 vaccination coverage for children whose mothers were born overseas. In 2011, WA had lower coverage among the Aboriginal population (89.5%) and children of young mothers (89.3%) compared to NSW (92.2 and 92.1% respectively). CONCLUSION: Despite overall high coverage of MMR1 vaccination, coverage inequalities increased especially for children of mothers born overseas. Strategic immunisation plans and policy interventions are important for equitable vaccination levels. Future policy should target children of mothers born overseas and Aboriginal children.

Trends in chronic hepatitis B prevalence in Australian women by country of birth, 2000 to 2016.

Routine antenatal screening for chronic hepatitis B (HBV) in countries with high migrant populations provides an opportunity to monitor trends in HBV prevalence and can inform estimates locally and in countries with limited seroprevalence data. We linked perinatal birth register records with HBV notifications in the largest Australian state, over the period 2000-2016. Among women aged 15-44 years, we estimated age-standardized chronic HBV prevalence overall and by country of birth and also estimated trends in age-standardized HBV prevalence over time using regression modelling. Among 903 831 women, 8001 linked to a chronic HBV infection record (overall age-standardized prevalence 0.76%, 95% CI: 0.74-0.78). Prevalence varied by country of birth with the highest estimates among women born in Sierra Leone (11.13%, 95% CI: 8.29-13.96), Taiwan (8.08%, 95% CI: 6.74%-9.43%), Cambodia (7.47%, 95% CI: 6.50%-8.45%) and Vietnam (7.36%, 95% CI: 6.97%-7.75%); more moderate estimates among women from North Korea (2.76%, 95% CI: 1.99-3.53) and Samoa (2.64%, 95% CI: 1.99%-3.29%); prevalence was 0.18% (95% CI: 0.17-0.19) in Australian-born women. Over 17 years, there were significant reductions in HBV prevalence among all women (from 0.88% in 2000 to 0.57% in 2016; P < .0001). Among women from high prevalence countries, the greatest absolute reductions were observed among those from Taiwan (10.1%, P < .001) followed by Tonga (5.4%, P < .001), whereas no reductions were observed for women born in Vietnam (P = .08), South Korea (P = .41) and Sudan (P = .06). In conclusion, routine antenatal HBV testing can be used to inform HBV prevalence estimates and vaccine programme impact in countries with limited surveillance and high migration to Australia.

Women's empowerment is associated with maternal nutrition and low birth weight: evidence from Bangladesh Demographic Health Survey.

BACKGROUND: The burden of maternal undernutrition and low birth weight (LBW) incurs enormous economic costs due to their adverse consequences. Women's empowerment is believed to be one of the key factors for attaining maternal and child health and nutritional goals. Our objective was to investigate the association of women's empowerment with maternal undernutrition and LBW. METHODS: We used nationally representative data from the Bangladesh Demographic Health Survey for 2011 and 2014. We analysed 27357 women and 9234 mother-child pairs. A women's empowerment index (WEI) was constructed using principal component analysis with five groups of indicators: a) education, b) access to socio-familial decision making, c) economic contribution and access to economic decision making, d) attitudes towards domestic violence and e) mobility. We estimated odds ratios as the measure of association between the WEI and the outcome measures using generalized estimating equations to account for the cluster level correlation. RESULTS: The overall prevalence of maternal undernutrition was 20% and LBW was 18%. The WEI was significantly associated with both maternal undernutrition and LBW with a dose-response relationship. The adjusted odds of having a LBW baby was 32% [AOR (95% CI): 0.68 (0.57, 0.82)] lower in the highest quartile of the WEI relative to the lowest quartile. Household wealth significantly modified the effect of the WEI on maternal nutrition; in the highest wealth quintile, the odds of maternal undernutrition was 54% [AOR (95% CI): 0.46 (0.33, 0.64)] lower while in the lowest wealth quintile the odds of undernutrition was only 18% [AOR (95% CI): 0.82 (0.67, 1.00)] lower comparing the highest WEI quartile with the lowest WEI quartile. However, the absolute differences in prevalence of undernutrition between the highest and lowest WEI quartiles were similar across wealth quintiles (6-8%). CONCLUSIONS: This study used a comprehensive measure of women's empowerment and provides strong evidence that low levels of women's empowerment are associated with maternal undernutrition as well as with delivering LBW babies in Bangladesh. Therefore, policies to increase empowerment of women would contribute to improved public health.

Seroprevalence of Q fever among metropolitan and non-metropolitan blood donors in New South Wales and Queensland, 2014-2015.

OBJECTIVES: To estimate the prevalence of exposure to the causative agent of Q fever (Coxiella burnetii) and of current infections among blood donors in Australia. DESIGN, SETTING: Cross-sectional study in metropolitan Sydney and Brisbane, and in non-metropolitan regions with high Q fever notification rates (Hunter New England in New South Wales; Toowoomba in Queensland). PARTICIPANTS: Blood donors attending Red Cross collection centres during October 2014 - June 2015 who provided sera and completed a questionnaire on Q fever vaccination status, diagnosis and knowledge, and exposure history. MAIN OUTCOME MEASURES: Age- and sex-standardised seroprevalence of phase II IgG antibodies to C. burnetii (indicating past exposure) and independent risk factors for seropositivity; presence of C. burnetii DNA (indicating current infection and risk of transmission by blood transfusion). RESULTS: 2740 donors (94.5% response rate) completed the questionnaire and supplied sera for analysis. Crude antibody seroprevalence was 3.6%. Standardised seroprevalence was higher in non-metropolitan than metropolitan regions (NSW, 3.7% v 2.8%; Queensland, 4.9% v 1.6%; statistically significant only in Queensland). Independent predictors of antibody seropositivity were regular contact with sheep, cattle, or goats (adjusted odds ratio [aOR], 5.3; 95% CI, 2.1-14), abattoir work (aOR, 2.2; 95% CI, 1.2-3.9), and assisting at an animal birth (aOR, 2.1; 95% CI, 1.2-3.6). Having lived in a rural area but having only rare or no contact with sheep, cattle or goats was itself a significant risk factor (v never lived rurally: aOR, 2.5; 95% CI, 1.1-5.9). 40% of people in groups recommended for vaccination were aware of the vaccine; 10% of people in these groups had been vaccinated. C. burnetii DNA was not detected in 1681 non-metropolitan samples, suggesting that transmission by blood donation is unlikely. CONCLUSIONS: Given their exposure to multiple risk factors, vaccination against Q fever should be considered for all rural residents.

Patterns of Drug Use and Drug-related Hospital Admissions in HIV-Positive and -Negative Gay and Bisexual Men.

We aimed to compare rates of illicit drug-related hospitalisations in HIV-negative (HIV-ve) (n = 1325) and HIV-positive (HIV+ve) (n = 557) gay and bisexual men (GBM) with rates seen in the general male population and to examine the association between self-reported illicit drug use and drug-related hospitalisation. Participants were asked how often they used a range of illicit drugs in the previous 6 months at annual interviews. Drug-related hospital admissions were defined as hospital admissions for mental or behavioural disorders due to illicit drug use (ICD 10: F11-16, F18, F19), drug poisoning (T40-T45, T50) or toxic effect of gases (T53, T59, T65). Drug-related hospitalisations were 4.8 times higher in the HIV-ve cohort [SIR 4.75 (95 % CI 3.30-6.91)] and 3.5 times higher in the HIV+ve cohort [SIR 3.51 (1.92-5.88)] compared with the general population. Periods of weekly drug use [IRR 1.86 (1.01-3.46)], poly-drug use [IRR 2.17 (1.07-4.38)] and cannabis use [low use-IRR 1.95 (1.01-3.77), high use-IRR 2.58 (1.29-5.16)] were associated with drug-related hospitalisation in both cohorts, as was being a consistently high meth/amphetamine user throughout follow-up [IRR 3.24 (1.07-9.83)] and being an inconsistent or consistent injecting drug user throughout follow-up [IRR 3.94 (1.61-9.66), IRR 4.43(1.04-18.76), respectively]. Other risk factors for drug-related hospitalisation indicated the likelihood of comorbid drug and mental health issues in GBM hospitalised for drug use.

Risk factors and burden of acute Q fever in older adults in New South Wales: a prospective cohort study.

OBJECTIVES: To measure the acute burden of and to identify risk factors associated with notified Q fever in older adults in New South Wales. DESIGN, SETTINGS AND PARTICIPANTS: A prospective cohort of adults aged 45 years and over (the 45 and Up Study) recruited during 2006-2009 and followed using linked Q fever notifications, hospital records and death records during 2006-2012. MAIN OUTCOME MEASURES: Incident cases of Q fever, based on a linked Q fever notification; proportion of cases with a Q fever-coded hospitalisation. RESULTS: A total of 266 906 participants were followed up for 1 254 650 person-years (mean, 4.7 ± 1.0 years per person). In our study population, the incidence of notified Q fever during follow-up was 3.6 (95% CI, 2.7-4.8) per 100 000 person-years. After adjustments, age (≥ 65 years v 45-54 years: hazard ratio [HR], 0.39; 95% CI, 0.16-0.96), sex (women v men: HR, 0.48; 95% CI, 0.26-0.88), and area and type of residence (P < 0.001 for trend) remained significantly associated with Q fever. Compared with those living in an inner regional area but not on a farm, the risk of notified Q fever was highest for those living on a farm in outer regional or remote areas (HR, 11.98; 95% CI, 5.47-26.21), followed by those living on a farm in inner regional areas (HR, 4.95; 95% CI, 1.79-13.65). Of notified Q fever cases, 15 of 39 (38%) had been hospitalised with a diagnosis consistent with Q fever. CONCLUSIONS: Adults living on a farm in outer regional and remote areas are at a substantially greater risk of contracting Q fever. This suggests that, as well as targeting specific occupational groups for vaccination, there would be benefits in increasing public awareness of Q fever and vaccination among those living on and near farms in outer regional and remote areas of Australia.

Estimating the measles effective reproduction number in Australia from routine notification data.

OBJECTIVE: To estimate the measles effective reproduction number (R) in Australia by modelling routinely collected notification data. METHODS: R was estimated for 2009-2011 by means of three methods, using data from Australia's National Notifiable Disease Surveillance System. Method 1 estimated R as 1 - P, where P equals the proportion of cases that were imported, as determined from data on place of acquisition. The other methods estimated R by fitting a subcritical branching process that modelled the spread of an infection with a given R to the observed distributions of outbreak sizes (method 2) and generations of spread (method 3). Stata version 12 was used for method 2 and Matlab version R2012 was used for method 3. For all methods, calculation of 95% confidence intervals (CIs) was performed using a normal approximation based on estimated standard errors. FINDINGS: During 2009-2011, 367 notifiable measles cases occurred in Australia (mean annual rate: 5.5 cases per million population). Data were 100% complete for importation status but 77% complete for outbreak reference number. R was estimated as < 1 for all years and data types, with values of 0.65 (95% CI: 0.60-0.70) obtained by method 1, 0.64 (95% CI: 0.56-0.72) by method 2 and 0.47 (95% CI: 0.38-0.57) by method 3. CONCLUSION: The fact that consistent estimates of R were obtained from all three methods enhances confidence in the validity of these methods for determining R.

Rapid identification of group B streptococcus carriage by PCR to assist in the management of women with prelabour rupture of membranes in term pregnancy.

BACKGROUND: Management of prelabour rupture of membranes at term (37 weeks gestation or later) (TPROM) remains complicated in the absence of a rapid assay for group B streptococcus (GBS) colonisation. AIMS: To evaluate the accuracy and clinical utility of a commercial PCR assay, compared with culture, for detection of GBS colonisation in pregnant women presenting with TPROM. METHODS: A prospective study of women presenting with TPROM conducted in a large tertiary hospital (Westmead Hospital, Australia). Five hundred and seventy-four consecutive women with TPROM were enrolled between July 2006 and November 2007. Paired low vaginal and anal swabs were collected from women presenting with TPROM for PCR and culture on GBS selective agar following broth enrichment. Primary outcomes were sensitivity and specificity of PCR compared with GBS selective enrichment culture. Secondary analyses included comparison with a historical but otherwise similar cohort regarding clinical utility, maternal and neonatal outcomes. RESULTS: PCR sensitivity and specificity were 89.0% (95% CI - 82.8-93.6%) and 97.9% (95% CI - 96.0-99.0%), respectively, compared with culture. 72.3% of women were aware of their GBS PCR status within 3 h of presentation. Compared with the historical cohort, PCR reduced the requirement for intrapartum antibiotics by 25.6% (P < 0.001). There were no significant differences in maternal outcomes or combined rates of admissions to neonatal intensive care or special care nursery. CONCLUSIONS: Group B streptococcus PCR is an accurate, rapid, safe and practical alternative to culture for detection of GBS colonisation in pregnant women at the time of TPROM. This method has the potential advantage to reduce costs associated with length of hospital stay.

Infant Whole-Cell Versus Acellular Pertussis Vaccination in 1997 to 1999 and Risk of Childhood Hospitalization for Food-Induced Anaphylaxis: Linked Administrative Databases Cohort Study.

BACKGROUND: Evidence suggests that children who had received an initial priming dose of whole-cell pertussis (wP) vaccine, rather than acellular pertussis (aP) vaccine, had a lower risk of developing IgE-mediated food allergy, the most common cause of anaphylaxis-related hospital presentations of childhood. OBJECTIVE: To assess the association between wP versus aP vaccination in infancy and subsequent hospital presentations for anaphylaxis. METHODS: This study was preregistered under PMID 34874968. Perinatal records for a cohort of New South Wales-born children (1997-1999) receiving their first dose of pertussis-containing vaccine before age 4 months were probabilistically linked to hospital and immunization records. We used adjusted Cox models to estimate hazard ratios (aHRs) and 95% CIs for anaphylaxis-coded hospitalizations. RESULTS: There were 218,093 New South Wales-born children who received a first dose of wP or aP before age 4 months. Among these children, 86 experienced at least one hospitalization for food-induced anaphylaxis at age 5-15 years (range of events per patient, one to three). The person-time of follow-up was 1,476,969 years, and 665,519 years for children vaccinated with wP as a first dose (wP-1 children) and aP as a first dose (aP-1 children), respectively. The incidence rates for first hospitalization for food anaphylaxis were 3.5 (95% CI, 2.6-4.6) and 5.1 (95% CI, 3.5-7.1) per 100,000 child-years among wP-1 children and aP-1 children, respectively (aHR for wP vs aP = 0.47; 95% CI, 0.26-0.83). For first admission for venom anaphylaxis, the incidence rate was 4.9 (95% CI, 3.9-6.2) per 100,000 child-years among wP-1 children and 5.1 (95% CI, 3.5-7.1) per 100,000 child-years among aP-1 children (aHR for wP vs aP = 0.92; 95% CI, 0.53-1.60), and for all-cause anaphylaxis, the incidence rate was 10.6 (95% CI, 9.0-12.4) per 100,000 child-years among wP-1 children and 12.8 (95% CI, 10.2-15.8) per 100,000 child-years among aP-1 children (aHR for wP vs aP = 0.92; 95% CI, 0.53-1.60). CONCLUSION: Vaccination with wP in infancy was associated with a lower risk of hospitalizations for food-induced anaphylaxis (and therefore severe IgE-mediated food allergy) occurring in childhood.

Measles, mumps, rubella and varicella antibodies among international and domestic university students.

BACKGROUND: Vaccine-preventable infections are generally well controlled in Australia. However, gaps in immunity can lead to outbreaks and are important to identify. Young adults are a highly mobile population and a potential source of imported infections. We aimed to evaluate anti- measles, mumps, rubella and varicella (MMR&V) IgG seroprevalence and explore factors relating to antibody seropositivity. METHODS: A cross-sectional online survey was conducted among students from a large Australian university to collect demographic, vaccination, infection and travel characteristics. Blood samples were collected to measure MMR&V seroprevalence. Logistic regression was used to identify factors associated with seropositivity. RESULTS: Among 804 university students, seroprevalence (positive or equivocal) for measles was 82.3% (95% CI 79.6-84.8%), mumps 79.5% (95% CI 76.7-82.3%), rubella 91.5% (95% CI 89.6-93.5%) and varicella 86.2% (95% CI 84.1-88.8%), with 452 (56.2%, 95% CI 52.8-59.6) seropositive to all four viruses. Varicella seropositivity was highest in the older birth cohort (born 1988-1991). Measles seropositivity was higher for international students compared to domestic students. Among international students, mumps seroprevalence was significantly lower than measles and rubella seroprevalence. International travel in the previous 12 months was reported by 63.1% of students, but only 18.2% of travellers reported seeking pre-travel health advice prior to most recent international travel. CONCLUSIONS: Overall, this study suggests immunity to MMR&V is sub-optimal. We found the university student population to be highly mobile and unlikely to seek pre-travel advice; thus, they are a potential source of infection importation. The implementation of university immunization policies could address the gaps identified and our findings can inform the development of targeted vaccination campaigns.

Country of birth and other factors associated with hepatitis B prevalence in a population with high levels of immigration.

BACKGROUND AND AIM: While hepatitis B virus (HBV) prevalence is known to vary greatly between countries, systematically collected population-level prevalence data from some countries is limited. Antenatal HBV screening programs in countries with substantial migrant populations provide the opportunity to systematically examine HBV prevalence in order to inform local and regional HBV estimates. METHODS: A comprehensive register of Australian mothers giving birth from January 2000 to December 2008 was linked to a register of HBV notifications. Age-standardized prevalence of chronic HBV were calculated overall and by the mother's country of birth. Multiple logistic regression was used to investigate other factors associated with HBV prevalence. RESULTS: Five hundred twenty-three thousand six hundred sixty-five women were included and linked to 3861 HBV notifications. The age-standardized HBV prevalence was low (0.75%, 95% confidence interval 0.72-0.79). The highest HBV prevalence rates were observed in women born in Cambodia (8.60%), Taiwan (8.10%), Vietnam (7.49%), China (6.80%), and Tonga (6.51%). Among Australia-born women, those who smoked during pregnancy, were from a more disadvantaged socioeconomic background, and lived in remote areas were more likely to have HBV. There was also a trend suggesting a decrease in the prevalence of HBV over time. CONCLUSIONS: Antenatal screening for HBV can provide systematic population estimates of HBV prevalence in migrants and also identify other high prevalence groups. Longer follow-up will be required to confirm the small decrease in HBV prevalence observed in this study.

Pneumococcal Conjugate Vaccines Are Protective Against Respiratory Syncytial Virus Hospitalizations in Infants: A Population-Based Observational Study.

Background: Pneumococcal conjugate vaccines (PCV) reduced the risk of respiratory syncytial virus (RSV) in a randomized clinical trial. We aimed to assess the real-world effectiveness of PCV on RSV-hospitalizations among Western Australian infants. Methods: We conducted a population-based cohort study of births during 2000-2012, using probabilistically linked individual-level immunization, hospitalization, respiratory microbiology testing, and perinatal data. We performed Cox proportional hazard models with time-varying exposure (receipt of infant PCV doses) against the first RSV-confirmed hospitalization 0-12 months adjusted for perinatal and sociodemographic factors. Results: From 360 994 children, 3-dose PCV coverage in Aboriginal infants ranged from 29% to 51% in 2001-2004 when PCV was funded for Aboriginal children only. Following universal funding in 2005, coverage increased to 85% for Aboriginal and 73% for non-Aboriginal infants. RSV-hospitalization rates were highest in young infants aged 0-5 months (22.5/1000 child-years) and >2 times higher in Aboriginal infants than in non-Aboriginal infants. Receipt of ≥3 PCV doses in the universal funded period was associated with a 30% reduction in RSV-hospitalization in Aboriginal infants (adjusted hazard ratio, aHR 0.70 [95% confidence interval, CI 0.46-1.06]) and 21% reduction in non-Aboriginal infants (aHR 0.79 [95% CI 0.63-0.99]) compared with unvaccinated infants. Conclusions: Prior to the introduction of RSV vaccines, our study suggests that universal childhood PCV vaccination may result in a reduction in severe RSV infections in children and may be important for countries that are yet to consider PCV programs.

Background incidence rates of selected adverse events of special interest (AESI) to monitor the safety of COVID-19 vaccines.

BACKGROUND: Determining background rates of medical conditions identified as adverse events of special interest (AESI) that may occur following COVID-19 vaccination is important for contextualising and investigating potential vaccine safety signals. METHODS: We conducted a retrospective population-based cohort study using linked emergency department, hospitalisation and death data for 2017 and 2018 from Australia's most populous state, New South Wales. Incident cases of select neurological conditions, arterial or venous thromboembolic conditions, secondary thrombocytopenia, myocarditis/pericarditis, and unique events of anaphylaxis and generalised convulsions were identified using internationally agreed upon diagnostic (ICD-10) codes. State-specific rates per 100,000 person-years were calculated, with further stratification by age group and sex where clinically relevant to the condition, and the number of expected cases nationally in one and 6 weeks was estimated. RESULTS: Background rates of selected neurological conditions were low with the exception of generalised convulsions for which 1,599-1,872 cases were estimated nationally in a 1-week period in the absence of vaccination. Using a narrow case definition, rates of Guillain-Barré Syndrome (3.9 per 100,000 person-years) were higher than international rates reported elsewhere. Thromboembolic and cerebral venous sinus thrombosis event rates increased with age. Myocarditis occurred more commonly in males, and was highest in males aged 18-24 years, with an estimated 1-4 cases expected nationally in a 1-week period. CONCLUSIONS: Using routinely collected linked healthcare data provides localised estimates of background rates of new onset or periodic AESI which enables rapid estimation of observed-versus-expected rates of events reported following COVID-19 vaccination. This Australian-specific analysis contributes AESI background rates which can be compared with those from other countries to enhance understanding of geographic variability in the frequency of specific AESI in the absence of vaccination, and can be utilised for signal detection during program implementation.

Non-specific benefit of seasonal influenza vaccine on respiratory syncytial virus-hospitalisations in children: An instrumental variable approach using population-based data.

BACKGROUND: Seasonal influenza vaccine is effective against influenza hospitalisations, but little is known about non-specific effects of the vaccine on other respiratory pathogens with similar seasonal patterns. We aimed to assess the causal impact of seasonal influenza vaccine on laboratory-confirmed hospitalisations for respiratory syncytial virus (RSV) in children using an instrumental variable (IV) strategy. METHODS: We used probabilistically linked population-based data on childhood immunisations, births, deaths, hospitalisations, perinatal factors, and microbiology test results (2000-2013) of all Western Australian (WA) children born 2000-2012, observed longitudinally until the earliest of 7 years of age or 31 December 2013. We exploited a unique natural experiment created from the WA's state-funded preschool influenza vaccination policy commencing in 2008 and used this as an instrument for children's seasonal influenza vaccination status. We estimated a system of two simultaneous probit equations: determinants of influenza vaccine uptake, and determinants of RSV-confirmed hospitalisation. RESULTS: Influenza vaccine coverage was low prior to 2008 but increased to 36 % in children aged 6-23 months in 2009. The majority (90 %) of RSV-hospitalisations occurred in children <2 years. Receipt of influenza vaccine reduced RSV-hospitalisations, especially in those <2 years with a rate reduction of 2.27 per 1000 (95 % CI: -3.26; -1.28), and a smaller rate reduction of 0.53 per 1000 (95 % CI: -1.04; -0.02) in those 2-7 years. Over the 5-year period (2008-2013), the state-funded preschool-influenza vaccine program resulted in 1,193 fewer RSV-hospitalisations. Of these, 793 (67 %) were in young children <2 years. CONCLUSIONS: To our knowledge, this is the first analysis utilising an IV estimation strategy on a population level to assess the causal impact of seasonal influenza vaccine on risk of RSV-hospitalisations. We estimated a small protective effect that warrants further investigation.