Impact of Meningococcal ACWY Vaccination Program during 2017-18 Epidemic, Western Australia, Australia.

The rising incidence of invasive meningococcal disease (IMD) caused by Neisseria meningitidis serogroup W in Western Australia, Australia, presents challenges for prevention. We assessed the effects of a quadrivalent meningococcal vaccination program using 2012-2020 IMD notification data. Notification rates peaked at 1.8/100,000 population in 2017; rates among Aboriginal and Torres Strait Islander populations were 7 times higher than for other populations. Serogroup W disease exhibited atypical manifestations and increased severity. Of 216 cases, 20 IMD-related deaths occurred; most (19/20) were in unvaccinated persons. After the 2017-2018 targeted vaccination program, notification rates decreased from 1.6/100,000 population in 2018 to 0.9/100,000 population in 2019 and continued to decline in 2020. Vaccine effectiveness (in the 1-4 years age group) using the screening method was 93.6% (95% CI 50.1%-99.2%) in 2018 and 92.5% (95% CI 28.2%-99.2%) in 2019. Strategic planning and prompt implementation of targeted vaccination programs effectively reduce IMD.

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.

Influenza vaccination in Western Australian children: Exploring the health benefits and cost savings of increased vaccine coverage in children.

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 < 5 years and routinely immunising school-aged children. Methods: A deterministic compartmental Susceptible-Exposed-Infectious-Recovered age-stratified transmission model was developed and calibrated using laboratory-notification and hospitalisation data. Base case vaccine coverage estimates were derived from 2019 data and tested under moderate, low and high vaccine effectiveness settings. The impact of increased coverage on the burden of influenza, influenza-associated presentations and net costs were assessed using the transmission model and estimated health utilisation costs. Results: Under base case vaccine coverage and moderate vaccine effectiveness settings, 225,460 influenza cases are expected annually across all ages. Direct healthcare costs of influenza were estimated to be A$27,608,286 per annum, dominated by hospital costs. Net cost savings of >$A1.5 million dollars were observed for every 10 % increase in vaccine coverage in children < 5 years. Additional benefits were observed by including primary school age children (5-11 years) in the funded influenza vaccination program - a reduction in cases, presentations, hospitalisations and approximately $A4 million net costs savings were observed for every 10 % increase in coverage. The further addition of older children (12-17 years) resulted in only moderate additional net cost savings figures, compared with a 5-11year-old program alone. Net costs savings were predominantly derived by a reduction in influenza-associated hospitalisation in adults. Conclusions: Any increase in influenza vaccine coverage in children < 5 years, above a base case of 50 % coverage resulted in a substantive reduction in influenza cases, presentations, hospitalisations and net costs when applied to the West Australian population. However, the most impactful pediatric program, from both a disease prevention and costs perspective, would be one that increased vaccination coverage among primary-school aged children.

Association between pertussis vaccination in infancy and childhood asthma: A population-based record linkage cohort study.

BACKGROUND: Asthma is among the commonest noncommunicable diseases of childhood and often occurs with other atopic comorbidities. A previous case-control study found evidence that compared to children who received acellular pertussis (aP) vaccines in early infancy, children who received one or more doses of whole-cell pertussis (wP) vaccine had lower risk of developing IgE-mediated food allergy. We hypothesized that wP vaccination in early infancy might protect against atopic asthma in childhood. METHODS: Retrospective record-linkage cohort study of children between 5 and < 15 years old and born between January 1997, and December 1999, in the Australian states of Western Australia (WA) and New South Wales (NSW), receiving wP versus aP vaccine as the first pertussis vaccine dose. The main outcome and measures were first and recurrent hospitalizations for asthma; hazard ratios (HRs) and 95% confidence intervals (CIs) were computed by means of Cox and Andersen and Gill models. RESULTS: 274,405 children aged between 5 and < 15 years old (78.4% NSW-born) received a first dose of either wP (67.8%) or aP vaccine before 4 months old. During the follow-up period, there were 5,905 hospitalizations for asthma among 3,955 children. The incidence rate for first hospitalization was 1.5 (95% CI 1.4-1.5) per 1,000 child-years among children receiving wP vaccine as a first dose, and 1.5 (95% CI 1.4-1.6) among those vaccinated with aP vaccine as a first dose. The adjusted HRs for those who received wP vaccine versus aP vaccine as the first dose were 1.02 (95% CI 0.94-1.12) for first hospitalizations and 1.07 (95% CI 0.95-1.2) for recurrent hospitalizations for asthma. CONCLUSIONS: We found no convincing evidence of a clinically relevant association between receipt of wP versus aP vaccines in early infancy and hospital presentations for asthma in childhood.

Finite element analysis to assess stress and deformation in bone with glass fiber-reinforced-poly-ether-ether-ketone, zirconia, and titanium implants.

Objectives: Recently, zirconia ceramic and glass or carbon fiber-reinforced poly-ether-ether-ketone (PEEK) composites have been introduced as newer implant biomaterials. This study was done to evaluate stress and deformation in bone with glass fiber-reinforced (GFR)-PEEK, zirconia, and titanium implants. Materials and Methods: A geometric model of mandibular molar replaced with implant-supported crown was generated. Implant of 12 mm length and 4.5 mm diameter was used in study. Finite element analysis models of implant assemblies of three materials GFR-PEEK, zirconium, and titanium were generated. 150 N loads were applied obliquely and vertically along the long axis of implant. Von Mises stresses and deformation generated were compared using ANSYS Workbench 17.0 and finite element software. Results: All three implant assemblies, i.e., GFR-PEEK, zirconia, and titanium, demonstrated similar stresses and deformation in bone without significant difference. Conclusion: It was concluded that GFR-PEEK and zirconia implants can be used as a substitute to titanium implants.

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.

Incremental effectiveness of 23-valent pneumococcal polysaccharide vaccine against pneumonia hospitalisation among Australian Indigenous children: A record linkage study.

BACKGROUND: The impact of pneumococcal conjugate vaccines (PCVs) on pneumonia in children is well-documented but data on 23-valent pneumococcal polysaccharide vaccine (PPV23) are lacking. Between 2001 and 2011, Indigenous children in Western Australia (WA) were recommended to receive PPV23 at 18-24 months of age following 3 doses of 7-valent PCV. We evaluated the incremental effectiveness of PPV23 against pneumonia hospitalisation. METHODS: Indigenous children born in WA between 2001 and 2012 who received PCV dose 3 by 12 months of age were followed from 18 to 60 months of age for the first episode of pneumonia hospitalisation (all-cause and 3 subgroups: presumptive pneumococcal, other specified causes, and unspecified). We used Cox regression modelling to estimate hazard ratios (HRs) for pneumonia hospitalisation among children who had, versus had not, received PPV23 between 18 and 30 months of age after adjustment for confounders. RESULTS: 11,120 children had 327 first episodes of all-cause pneumonia hospitalisation, with 15 (4.6%) coded as presumptive pneumococcal, 46 (14.1%) as other specified causes and 266 (81.3%) unspecified. No statistically significant reduction in all-cause pneumonia was seen with PPV23 (HR 1.11; 95% CI: 0.87-1.43), but the direction of the association differed for presumptive pneumococcal (HR 0.47; 95% CI: 0.16-1.35) and specified (HR 0.89; 95% CI: 0.49-1.62) from unspecified causes (HR 1.13; 95% CI: 0.86-1.49). During the baseline period before PPV23 vaccination (12-18 months), all-cause pneumonia risk was higher among PPV23-vaccinated than unvaccinated children (RR: 1.73; 95% CI: 1.30-2.28). CONCLUSION: In this high-risk population, no statistically significant incremental effect of a PPV23 booster at 18-30 months was observed against hospitalised all-cause pneumonia or the more specific outcome of presumptive pneumococcal pneumonia. Confounding by indication may explain the slight trend towards an increased risk against all-cause pneumonia. Larger studies with better control of confounding are needed to further inform PPV23 vaccination.

Predicting the causative pathogen among children with pneumonia using a causal Bayesian network.

BACKGROUND: Pneumonia remains a leading cause of hospitalization and death among young children worldwide, and the diagnostic challenge of differentiating bacterial from non-bacterial pneumonia is the main driver of antibiotic use for treating pneumonia in children. Causal Bayesian networks (BNs) serve as powerful tools for this problem as they provide clear maps of probabilistic relationships between variables and produce results in an explainable way by incorporating both domain expert knowledge and numerical data. METHODS: We used domain expert knowledge and data in combination and iteratively, to construct, parameterise and validate a causal BN to predict causative pathogens for childhood pneumonia. Expert knowledge elicitation occurred through a series of group workshops, surveys and one-on-one meetings involving 6-8 experts from diverse domain areas. The model performance was evaluated based on both quantitative metrics and qualitative expert validation. Sensitivity analyses were conducted to investigate how the target output is influenced by varying key assumptions of a particularly high degree of uncertainty around data or domain expert knowledge. RESULTS: Designed to apply to a cohort of children with X-ray confirmed pneumonia who presented to a tertiary paediatric hospital in Australia, the resulting BN offers explainable and quantitative predictions on a range of variables of interest, including the diagnosis of bacterial pneumonia, detection of respiratory pathogens in the nasopharynx, and the clinical phenotype of a pneumonia episode. Satisfactory numeric performance has been achieved including an area under the receiver operating characteristic curve of 0.8 in predicting clinically-confirmed bacterial pneumonia with sensitivity 88% and specificity 66% given certain input scenarios (i.e., information that is available and entered into the model) and trade-off preferences (i.e., relative weightings of the consequences of false positive versus false negative predictions). We specifically highlight that a desirable model output threshold for practical use is very dependent upon different input scenarios and trade-off preferences. Three commonly encountered scenarios were presented to demonstrate the potential usefulness of the BN outputs in various clinical pictures. CONCLUSIONS: To our knowledge, this is the first causal model developed to help determine the causative pathogen for paediatric pneumonia. We have shown how the method works and how it would help decision making on the use of antibiotics, providing insight into how computational model predictions may be translated to actionable decisions in practice. We discussed key next steps including external validation, adaptation and implementation. Our model framework and the methodological approach can be adapted beyond our context to broad respiratory infections and geographical and healthcare settings.

Review of the health impact of the oral rotavirus vaccine program in children under 5 years in Australia: 2006 - 2021.

Oral rotavirus vaccines were incorporated into the National Immunisation Program (NIP) for all Australian infants in July 2007. Initially each of the eight jurisdictions implemented Rotarix or RotaTeq rotavirus vaccine, however from July 2017 all states and territories have administered Rotarix only. This review evaluates the health impact of the oral rotavirus vaccine program for Australian children less than 5 years old over the first 15 years of the rotavirus vaccine program, observing long-term changes in rotavirus-related health care attendances, public health notifications, and vaccine effectiveness and safety data for both Rotarix and RotaTeq rotavirus vaccines. We searched Medline for studies published between January 2006 and May 2022 using the search terms 'rotavirus', 'rotavirus vaccine' and 'Australia'. Of 491 items identified, 76 items - 36 peer-reviewed articles and 40 reports - were included in the review. We found evidence that the introduction of the oral rotavirus vaccine program in Australia was associated with a prompt reduction in rotavirus-coded and all-cause gastroenteritis hospitalisations of vaccine-eligible children. In the context of less complete coverage, reduced vaccine timeliness and lower vaccine effectiveness, a less substantial and inconsistent reduction in severe rotavirus disease was observed among Aboriginal and Torres Strait Islander children, particularly those living in rural and remote northern Australia. Additional studies report no evidence for the emergence of non-vaccine serotypes and/ or replacement serotypes in Australia during the vaccine era. While the health impact for young children and consequent cost-savings of the oral rotavirus vaccine program have been high, it is important to find strategies to improve rotavirus vaccine impact for Aboriginal and Torres Strait Islander populations to ensure health benefits for all Australian children.

Systematic review of the effect of additional doses of oral rotavirus vaccine on immunogenicity and reduction in diarrhoeal disease among young children.

Background: Oral rotavirus vaccines have lower effectiveness in high child mortality settings. We evaluated the impact of additional dose(s) schedules of rotavirus vaccine on vaccine immunogenicity and reduction in episodes of gastroenteritis. Methods: We searched Medline (via PubMed), Cochrane databases and ClinicalTrials.gov for randomised controlled trials from 1973 to February 2022, evaluating the immunological and clinical impact of additional dose vs standard dose oral rotavirus vaccine schedules. We extracted immunogenicity - proportion of children with evidence of anti-rotavirus IgA seroresponse, and clinical - proportion of children with at least one episode of severe rotavirus gastroenteritis, outcome data and used random effects meta-analysis where appropriate. We assessed the methodological quality of the studies using the Cochrane risk of bias tool. The study protocol was registered in PROSPERO (CRD42021261058). Findings: We screened 536 items and included 7 clinical trials. Our results suggest moderate to high level evidence that an additional dose rotavirus vaccine schedule improves IgA vaccine immune response, including additional doses administered as a booster dose schedule >6 months old; IgA vaccine seroresponse 74·3% additional dose schedule vs 56·1% standard dose schedule RR 1·3 (95%CI, 1·15 - 1·48), and when administered to children who were seronegative at baseline; IgA vaccine seroresponse 48.2% additional dose schedule vs 29.6% standard dose schedule RR 1.86 (95%CI 1.27 to 2.72). Only one study evaluated reduction in gastroenteritis episodes and found little benefit in first year of life, 1·8% vs 2·0% RR 0·88 (95% CI, 0·52 to 1·48), or second year of life, 1·7% vs 2·9% RR 0·62 (95%CI, 0·31 - 1·23). Interpretation: Administering an additional dose of oral rotavirus vaccines is likely to result in an improved vaccine immune response, including when administered as a booster dose to older children. Evidence of an impact on diarrhoeal disease is needed before additional dose rotavirus vaccine schedules can be recommended as vaccine policy. Funding: BM was funded by the National Health and Medical Research Council, the Royal Australasian College of Physicians Paediatrics and Child Health Division, and the Australian Academy of Science.

Effectiveness of 7-Valent Pneumococcal Conjugate Vaccine Against Invasive Pneumococcal Disease in Medically At-Risk Children in Australia: A Record Linkage Study.

BACKGROUND: Children with chronic medical conditions are at higher risk of invasive pneumococcal disease (IPD), but little is known about the effectiveness of the primary course of pneumococcal conjugate vaccine (PCV) in these children. METHODS: A cohort born in 2001-2004 from two Australian states and identified as medically at-risk (MAR) of IPD either using ICD-coded hospitalizations (with conditions of interest identified by 6 months of age) or linked perinatal data (for prematurity) were followed to age 5 years for notified IPD by serotype. We categorized fully vaccinated children as either receiving PCV dose 3 by <12 months of age or ≥1 PCV dose at ≥12 months of age. Cox proportional hazard modeling was used to estimate hazard ratios (HRs), adjusted for confounders, and vaccine effectiveness (VE) was estimated as (1-HR) × 100. RESULTS: A total of 9220 children with MAR conditions had 53 episodes of IPD (43 vaccine-type); 4457 (48.3%) were unvaccinated and 4246 (46.1%) were fully vaccinated, with 1371 (32.3%) receiving dose 3 by 12 months and 2875 (67.7%) having ≥1 dose at ≥12 months. Estimated VE in fully vaccinated children was 85.9% (95% CI: 33.9-97.0) against vaccine-type IPD and 71.5% (95% CI: 26.6-88.9) against all-cause IPD. CONCLUSION: This is the first population-based study evaluating the effectiveness of PCV in children with MAR conditions using record linkage. Our study provides evidence that the VE for vaccine-type and all-cause IPD in MAR children in Australia is high and not statistically different from previously reported estimates for the general population. This method can be replicated in other countries to evaluate VE in MAR children.

Pertussis burden and acellular pertussis vaccine effectiveness in high risk children.

BACKGROUND: Pertussis hospitalisation is more common among infants born prematurely, who have significant comorbidities, or are Indigenous, but acellular pertussis (aP) vaccine effectiveness (VE) estimates in these sub-groups are lacking. We measured aP VE by Indigenous status, and policy-relevant categories of prematurity and comorbidity, in a population-based Australian cohort. METHODS: Perinatal, disease notification, hospitalisation, mortality, and vaccination data were linked to birth records in two Australian states (Western Australia and New South Wales) 2001-2012, with follow-up to the end of 2013. Children followed to 18 months of age were stratified by Aboriginality, prematurity (<32 vs 32-<37 weeks gestation) and comorbidities identified from hospital discharge coding. Rates, rate ratios and VE were calculated for first episode of hospitalised and non-hospitalised pertussis notifications using adjusted Cox proportional hazards models. RESULTS: Among >1,300,000 children, 63,867 (4·9%) were Aboriginal, 47,721 (3·6%) had at least one comorbidity and 3,771 first episodes of notified pertussis occurred <18 months of age; of these, 1,207 (32.0%) had an associated pertussis-coded hospitalisation. For hospitalised pertussis in Aboriginal and non-Aboriginal children, there was significant protection post dose 1 (VE 51% v 25%), 2 (VE 69% v 74%) and 3 (VE 76% v 80%). For children with co-morbidities, VE for hospitalised pertussis was low and non-significant post dose 1 (0%) and 2 (30%). Post dose 3, VE was significant for hospitalised pertussis (70%; 95% CI 29-87) but not for non-hospitalised pertussis (24%; 95% CI -49 to 61). CONCLUSIONS: For most Aboriginal and non-Aboriginal children, improved timeliness of current infant doses and higher antenatal coverage should further improve protection against pertussis of any severity. For children at highest risk of severe pertussis (born <32 weeks gestation or with significant medical comorbidities), our data suggest that additional measures-such as extra doses of pertussis-containing vaccines and/or vaccines with improved immunogenicity-are needed for protection.

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.

Pertussis immunisation in infancy and atopic outcomes: A protocol for a population-based cohort study using linked administrative data.

INTRODUCTION: The burden of IgE-mediated food allergy in Australian born children is reported to be among the highest globally. This illness shares risk factors and frequently coexists with asthma, one of the most common noncommunicable diseases of childhood. Findings from a case-control study suggest that compared to immunisation with acellular pertussis vaccine, early priming of infants with whole-cell pertussis vaccine may be associated with a lower risk of subsequent IgE-mediated food allergy. If whole-cell vaccination is protective of food allergy and other atopic diseases, especially if protective against childhood asthma, the population-level effects could justify its preferential recommendation. However, the potential beneficial effects of whole-cell pertussis vaccination for the prevention of atopic diseases at a population-scale are yet to be investigated. METHODS AND ANALYSIS: Analyses of population-based record linkage data will be undertaken to compare the rates of admissions to hospital for asthma in children aged between 5 and 15 years old, who were born in Western Australia (WA) or New South Wales (NSW) between 1997 and 1999 (329,831) when pertussis immunisation in Australia transitioned from whole-cell to acellular only schedules. In the primary analysis we will estimate hazard ratios and 95% confidence intervals for the time-to-first-event (hospital admissions as above) using Cox proportional hazard models in recipients of a first dose of whole-cell versus acellular pertussis-containing vaccine before 112 days old (~4 months of age). Similarly, we will also fit time-to-recurrent events analyses using Andersen-Gill models, and robust variance estimates to account for potential within-child dependence. Hospitalisations for all-cause anaphylaxis, food anaphylaxis, venom, all-cause urticaria and atopic dermatitis will also be examined in children who received at least one dose of pertussis-containing vaccine by the time of the cohort entry, using analogous statistical methods. Presentations to the emergency departments will be assessed separately using the same statistical approach.

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.

Safety of live attenuated herpes zoster vaccine in Australian adults 70-79 years of age: an observational study using active surveillance.

OBJECTIVES: To assess the safety of live attenuated herpes zoster vaccine live (ZVL) through cumulative analysis of near real-time, participant-based active surveillance from Australia's AusVaxSafety system. DESIGN AND SETTING: ZVL was funded in Australia for adults aged 70 years from November 2016, with a time-limited catch up programme for those up to 79 years. This cohort study monitored safety in the first two programme years through active surveillance at 246 sentinel surveillance immunisation sites. PARTICIPANTS: Adults aged 70-79 years vaccinated with ZVL who responded to an opt-out survey sent via automated short message service (SMS) 3 days following vaccination (n=17 458) or contributed supplementary data through a separate, opt-in online survey at 16 and 24 days following vaccination (n=346). PRIMARY AND SECONDARY OUTCOME MEASURES: Rates of overall and prespecified adverse events following immunisation (AEFI) by sex, concomitant vaccination and underlying medical condition. Signal detection methods (fast initial response cumulative summation and Bayesian updating analyses) were applied to reports of medical attendance. RESULTS: The median age of participants was 72 years; 53% were female. The response rate following automated SMS was high (73% within 7 days of vaccination). Females were more likely than males to report any adverse event within 7 days of vaccination (RR 2.07, 95% CI 1.86 to 2.31); injection site reaction was the most commonly reported (2.3%, n=377). Concomitant vaccination was not associated with higher adverse event rates (RR 1.05, 95% CI 0.93 to 1.18). Rates of medical attendance were low (0.3%) with no safety signals identified. Supplementary opt-in survey data on later onset adverse events did not identify any difference in AEFI rates between those with and without underlying medical conditions. CONCLUSIONS: ZVL has a very good safety profile in the first week after vaccination in older adults. Active, participant-based surveillance in this primary care cohort is an effective method to monitor vaccine safety among older adults and will be used as a key component of COVID-19 vaccine safety surveillance in Australia.

Estimating pneumococcal vaccine coverage among Australian Indigenous children and children with medically at-risk conditions using record linkage.

BACKGROUND: Risk-based recommendations are common for pneumococcal vaccines but little is known about their uptake. In Australia, pneumococcal conjugate vaccine (PCV) was funded only for Aboriginal or Torres Strait Islander (Indigenous) children and those with underlying medical conditions in 2001, and then there were different booster dose recommendations depending on risk after the introduction of universal PCV vaccination in 2005. METHODS: We measured coverage of PCV dose 3 and additional PCV and 23-valent pneumococcal polysaccharide vaccine (PPV23) doses by risk group among children born in July 2001-December 2012 in two Australian states using linked immunisation and hospitalisation data (available until December 2013). We ascertained medical risk conditions using hospitalisation diagnosis codes and Indigenous status using an established algorithm, comparing coverage for children born pre (2001-2004) and post (2005-2012) universal PCV funding. RESULTS: Among 1.3 million children, 63,897 (4.9%) were Indigenous and 32,934 (2.5%) had at least one medically at-risk condition identified by age 6 months. For births in 2001-2004, coverage for PCV dose 3 by 1 year of age was 37% for Indigenous, 15% for medically at-risk and 11% in other children, increasing to 83%, 91% and 92%, respectively for births in 2005-2012. In children with medically at-risk conditions, PCV dose 4 coverage by 2 years was 1% for 2001-2004 births, increasing to 9% for 2005-2012 births, with PPV23 coverage by 6 years 3% in both cohorts. Among eligible Indigenous children, PPV23 coverage by 3 years was 45% for 2001-2004 births and 51% for 2005-2012 births. CONCLUSIONS: Coverage with additional recommended booster doses was very low among children with medical conditions, and only modest among Indigenous children. If additional PCV doses are recommended for some risk groups, especially in the context of routine schedules with reduced doses (e.g. 2 + 1 and 1 + 1), measures to improve implementation will be required.

Impact of Rotavirus Vaccines on Gastroenteritis Hospitalizations in Western Australia: A Time-series Analysis.

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 <5 years (up to 79% among non-Aboriginal and up to 66% among Aboriginal). Among adults aged ≥65 years, rotavirus-coded hospitalizations were 89% (95% confidence interval, 16-187%) higher in the rotavirus vaccination program period. The time-series analysis suggested reductions in all-cause gastroenteritis hospitalizations in the post-vaccination period among both vaccinated and unvaccinated (age-ineligible) children, with increases observed in adults aged ≥45 years. CONCLUSIONS: Rotavirus vaccination has been associated with a significant decline in gastroenteritis hospitalizations among children. The increase in the elderly requires further evaluation, including assessment of the cost-benefits of rotavirus vaccination in this population.

Mode of birth and risk of infection-related hospitalisation in childhood: A population cohort study of 7.17 million births from 4 high-income countries.

BACKGROUND: The proportion of births via cesarean section (CS) varies worldwide and in many countries exceeds WHO-recommended rates. Long-term health outcomes for children born by CS are poorly understood, but limited data suggest that CS is associated with increased infection-related hospitalisation. We investigated the relationship between mode of birth and childhood infection-related hospitalisation in high-income countries with varying CS rates. METHODS AND FINDINGS: We conducted a multicountry population-based cohort study of all recorded singleton live births from January 1, 1996 to December 31, 2015 using record-linked birth and hospitalisation data from Denmark, Scotland, England, and Australia (New South Wales and Western Australia). Birth years within the date range varied by site, but data were available from at least 2001 to 2010 for each site. Mode of birth was categorised as vaginal or CS (emergency/elective). Infection-related hospitalisations (overall and by clinical type) occurring after the birth-related discharge date were identified in children until 5 years of age by primary/secondary International Classification of Diseases, 10th Revision (ICD-10) diagnosis codes. Analysis used Cox regression models, adjusting for maternal factors, birth parameters, and socioeconomic status, with results pooled using meta-analysis. In total, 7,174,787 live recorded births were included. Of these, 1,681,966 (23%, range by jurisdiction 17%-29%) were by CS, of which 727,755 (43%, range 38%-57%) were elective. A total of 1,502,537 offspring (21%) had at least 1 infection-related hospitalisation. Compared to vaginally born children, risk of infection was greater among CS-born children (hazard ratio (HR) from random effects model, HR 1.10, 95% confidence interval (CI) 1.09-1.12, p < 0.001). The risk was higher following both elective (HR 1.13, 95% CI 1.12-1.13, p < 0.001) and emergency CS (HR 1.09, 95% CI 1.06-1.12, p < 0.001). Increased risks persisted to 5 years and were highest for respiratory, gastrointestinal, and viral infections. Findings were comparable in prespecified subanalyses of children born to mothers at low obstetric risk and unchanged in sensitivity analyses. Limitations include site-specific and longitudinal variations in clinical practice and in the definition and availability of some data. Data on postnatal factors were not available. CONCLUSIONS: In this study, we observed a consistent association between birth by CS and infection-related hospitalisation in early childhood. Notwithstanding the limitations of observational data, the associations may reflect differences in early microbial exposure by mode of birth, which should be investigated by mechanistic studies. If our findings are confirmed, they could inform efforts to reduce elective CS rates that are not clinically indicated.

RSV prophylaxis use in high-risk infants in Western Australia, 2002-2013: a record linkage cohort study.

BACKGROUND: The monoclonal antibody, palivizumab is licensed for use in high-risk infants to prevent severe illness caused by respiratory syncytial virus (RSV). The level of its use and compliance with current jurisdictional guidelines which were amended in 2010, is unknown. We determined the level of palivizumab use in a cohort of high-risk infants in Western Australia. METHODS: Using probabilistically linked administrative data, we conducted a birth cohort study within tertiary neonatal intensive care units (NICUs) born between 2002 and 2013. We described palivizumab use by patient characteristics, eligibility criteria according to guidelines over the period of study and identified predictors of its use. RESULTS: Of 24,329 infants admitted to tertiary NICUs, 271 (1.1%) were dispensed 744 palivizumab doses with 62.5% being dispensed to infants born 2010-2013. The median number of doses received was 2. A total of 2679 infants met at least one of three criteria for palivizumab (criteria 1: gestational age at birth < 28 weeks and chronic lung disease; criteria 2: gestational age < 28 weeks and Aboriginal; criteria 3: congenital heart disease not otherwise in criteria 1 or 2). The extent of palivizumab use differed across the 3 groups. Of 803 infants meeting criteria 1, 21.8% received at least 1 dose of palivizumab; 52.8% from 2010 onwards. From 174 infants meeting criteria 2, 14.4% received at least 1 dose; 43.1% from 2010 onwards and from 1804 births meeting criteria 3, only 3.7% received at least 1 dose; 5.4% from year of birth 2010 onwards). In adjusted analyses, being born after 2010, being extreme preterm, chronic lung disease, congenital lung disease and being born in autumn or winter were independent predictors of palivizumab use. CONCLUSION: In this high-risk setting and notwithstanding the limitations of our data sources, the level of compliance of palivizumab use against current guidelines was low. Most doses were dispensed to infants meeting at least one high-risk criterion. Evidence of incomplete dosing is an important finding in light of recent developments of single dose monoclonal antibodies offering longer protection.