Burden of Illness Associated With Respiratory Syncytial Virus, Influenza, and Coronavirus Disease 2019 in Infants and Young Children in Ontario, Canada, 2018-2023: A Population-Based Canadian Immunization Research Network Study.

Background: As severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) transitions to endemicity and respiratory syncytial virus (RSV) and influenza reestablish their seasonal circulation patterns, understanding their comparative burden on infants and children can guide health system responses and funding priorities. Methods: This was a population-based cohort study of children aged <5 years in Ontario, Canada, from September 2018 to August 2023 using linked health administrative databases. Results: Seasonal cohorts comprised 731 838 to 763 660 children. RSV- and influenza-related hospital admission rates immediately decreased in March 2020. In 2021-2022, RSV-related admissions rebounded but remained 8%-11% lower than prepandemic seasons, whereas 2022-2023 RSV-related admissions increased 105%-113% versus prepandemic seasons and peak admissions occurred in November versus December. Influenza did not rebound until 2022-2023, when admissions were 28%-37% higher than prepandemic seasons. Coronavirus disease 2019 (COVID-19)-related admissions remained low until 2021-2022 and were lower than RSV-related admissions across all age groups during prepandemic and pandemic seasons. By contrast, 2021-2022 COVID-19-related admissions exceeded prepandemic influenza-related admissions by 30%-40% but decreased by 45% in 2022-2023 and were lower than prepandemic influenza-related admissions, except among infants aged <12 months who remained at highest risk. There was no distinct seasonal pattern for COVID-19-related admissions during the study. Conclusions: RSV remains a major cause of childhood hospitalization. Although COVID-19 appears to be receding, its disease burden as it transitions to endemicity remains to be established. The unprecedented peaks in RSV-related hospital admissions during 2022-2023, together with the return of influenza and ongoing SARS-CoV-2 transmission, underscore the need to strengthen systems for real-time surveillance and to proactively prepare for critical healthcare scenarios.

Neighborhood-Level Burden of Social Risk Factors on Respiratory Syncytial Virus Hospitalization in Ontario, Canada, 2016-2019.

Background: Beyond clinical risk factors, little is known about the impact of social determinants on respiratory syncytial virus (RSV) burden. Our study aimed to estimate RSV-related hospitalization rates across sociodemographic and housing characteristics. Methods: We conducted a population-based study of all RSV-related hospitalizations in Ontario, Canada, between September 1, 2016, and August 31, 2019, using validated hospital discharge codes and census data. Crude and age-standardized annualized RSV incidence rates and rate ratios (RRs) were estimated for a range of individual-level demographics and neighborhood-level measures of marginalization and housing characteristics. Results: Overall, the annual RSV-related hospitalization rate was 27 per 100 000, with the highest rates observed in children age <12 months (1049 per 100 000) and 12-23 months (294 per 100 000) and adults age ≥85 years (155 per 100 000). Higher RSV-related hospitalization rates were associated with increasing marginalization quintile (Q) of material resources (RR, 1.4; Q5: 33 per 100 000 vs Q1: 24 per 100 000) and household instability (RR, 1.5; Q5: 31 per 100 000 vs Q1: 22 per 100 000). Conclusions: The burden of RSV-related hospitalization was greatest in young children and older adults, with variation by sociodemographic and housing factors. Understanding the role of these social factors is crucial for informing equitable preventive program delivery.

Live Rotavirus Vaccination Appears Low-risk in Infants Born to Mothers With Inflammatory Bowel Disease on Biologics.

BACKGROUND & AIMS: Biologic therapies in the context of inflammatory bowel disease and pregnancy lead to improved maternal and fetal outcomes. Placental transfer results in detectable drug concentrations in infants. Rotavirus infection results in diarrheal related hospitalizations; however, the live oral vaccine is not currently recommended in biologic exposed infants. The aim of this study was to assess the effect of maternal biologic therapies on the infant immune system and safety of live rotavirus vaccination in biologic-exposed infants. METHODS: Biologic-exposed infants underwent standardized clinical assessments, drug concentration, and immune function testing (complete blood count, differential, immunoglobulin levels, extended B-cell and T-cell subset enumeration, Recent Thymic Emigrants, regulatory T-cell numbers, mitogen stimulation assays, and review of T-cell Receptor Excision Circles in the newborn screen). Rotavirus vaccine-specific adverse effects following immunizations up to 42 days post the last dose of the vaccine series were recorded. RESULTS: There were 57 infants born to 52 mothers with inflammatory bowel disease exposed to infliximab (n = 21), adalimumab (n = 19), vedolizumab (n = 10), and ustekinumab (n = 7) in the third trimester for a median of 39 weeks (interquartile range, 38-39 weeks) at delivery. Immunologic assessments validated for age were normal in all infants despite median infliximab concentrations of 6.1 ug/mL (range, 0.4-28.8 ug/mL), adalimumab concentrations of 1.7 ug/mL (range, 0.7-7.9 ug/mL), ustekinumab concentrations of 0.6 ug/mL (range, 0-1.1), and undetectable for vedolizumab at 10.7 weeks (interquartile range, 9.4-12.4) of age. The live oral rotavirus vaccine series was provided to 50 infants with the first dose given at a median of 13 weeks of age. No adverse effects following immunization were reported. CONCLUSION: Immune function testing was normal, and administration of live rotavirus vaccination appeared low-risk in biologic-exposed infants irrespective of circulating drug levels.

Canada's approach to SARS-CoV-2 sero-surveillance: Lessons learned for routine surveillance and future pandemics.

SETTING: In Canada's federated healthcare system, 13 provincial and territorial jurisdictions have independent responsibility to collect data to inform health policies. During the COVID-19 pandemic (2020-2023), national and regional sero-surveys mostly drew upon existing infrastructure to quickly test specimens and collect data but required cross-jurisdiction coordination and communication. INTERVENTION: There were 4 national and 7 regional general population SARS-CoV-2 sero-surveys. Survey methodologies varied by participant selection approaches, assay choices, and reporting structures. We analyzed Canadian pandemic sero-surveillance initiatives to identify key learnings to inform future pandemic planning. OUTCOMES: Over a million samples were tested for SARS-CoV-2 antibodies from 2020 to 2023 but siloed in 11 distinct datasets. Most national sero-surveys had insufficient sample size to estimate regional prevalence; differences in methodology hampered cross-regional comparisons of regional sero-surveys. Only four sero-surveys included questionnaires. Sero-surveys were not directly comparable due to different assays, sampling methodologies, and time-frames. Linkage to health records occurred in three provinces only. Dried blood spots permitted sample collection in remote populations and during stay-at-home orders. IMPLICATIONS: To provide timely, high-quality information for public health decision-making, routine sero-surveillance systems must be adaptable, flexible, and scalable. National capability planning should include consortiums for assay design and validation, defined mechanisms to improve test capacity, base documents for data linkage and material transfer across jurisdictions, and mechanisms for real-time communication of data. Lessons learned will inform incorporation of a robust sero-survey program into routine surveillance with strategic sampling and capacity to adapt and scale rapidly as a part of a comprehensive national pandemic response plan.

RéSUMé: CONTEXTE: Au Canada, où le système de santé est fédéré, les 13 juridictions provinciales et territoriales ont la responsabilité individuelle de recueillir les données qui leur permettent d'élaborer leurs politiques de santé. Lors de la pandémie de COVID-19 (2020­2023), pour réaliser les enquêtes de séroprévalence à l'échelle régionale et nationale, les autorités ont principalement utilisé l'infrastructure existante pour pouvoir analyser les échantillons et recueillir des données rapidement, mais cela a également nécessité de la communication et de la coordination entre les différentes juridictions. INTERVENTION: Au Canada, il y a eu quatre enquêtes nationales et sept enquêtes régionales sur la séroprévalence du SARS-CoV-2 dans la population générale. Les méthodologies utilisées différaient selon la méthode de sélection des participants, le choix des tests d'analyses et les structures de rapports. Nous avons analysé la façon dont ces enquêtes avaient été réalisées afin d'en dégager des éléments essentiels qui permettront de planifier pour les futures pandémies. RéSULTATS: Entre 2020 et 2023, plus d'un million d'échantillons, répartis en 11 ensembles de données distincts, ont été analysés afin de rechercher la présence d'anticorps au SARS-CoV-2. Dans la plupart des enquêtes nationales, la taille de l'échantillon était insuffisante pour pouvoir estimer la prévalence à l'échelle régionale. La disparité des méthodologies utilisées a entravé la comparaison des enquêtes régionales. Seules quatre enquêtes fournissaient les données recueillies à partir des questionnaires. Il a été impossible de comparer les enquêtes entre elles en raison de la diversité des tests d'analyse utilisés, des méthodes d'échantillonnage et de la durée des enquêtes. Seules trois provinces avaient couplé leurs données avec les archives médicales. Pour réaliser les enquêtes dans les populations éloignées et lors des périodes de confinement, la méthode d'analyse sur gouttes de sang séché a été utilisée. CONCLUSION: Afin de pouvoir fournir, en temps et en heure, des données de haute qualité pour la prise de décisions en matière de santé publique, un système de sérosurveillance continuelle doit être adaptable, modulable et évolutif. En cas de pandémie, un plan national doit prévoir des consortiums pour la conception et la validation des tests d'analyse, des moyens d'amélioration de la capacité de dépistage, des documents de base pour le couplage des données, un mode de transfert du matériel entre les différentes juridictions et des moyens pour une communication en temps réel des données. Les leçons tirées de cette analyse permettront de mettre en place un solide programme d'enquêtes de séroprévalence au sein des systèmes de sérosurveillance continuelle, et que ce programme sera accompagné d'une stratégie d'échantillonnage et d'un plan d'intervention national, rapide et complet en cas de pandémie.

Revaccination outcomes among adolescents and adults with suspected hypersensitivity reactions following COVID-19 vaccination: A Canadian immunization research network study.

BACKGROUND: COVID-19 vaccination has been associated with anaphylaxis and hypersensitivity reactions. Infectious disease physicians and allergists in the Canadian Special Immunization Clinic (SIC) Network developed guidance for evaluating patients with adverse events following immunization (AEFI) including suspected hypersensitivity. This study evaluated management and adverse event recurrence following subsequent COVID-19 vaccinations. METHODS: Individuals aged 12 years and older enrolled at participating SICs before February 28, 2023 who were referred for suspected or diagnosed hypersensitivity reaction following COVID-19 vaccination, or for prevaccination assessment of suspected allergy to a COVID-19 vaccine component were included. De-identified clinical assessments and revaccination data, captured in a centralized database, were analyzed. The Brighton Collaboration case definition (BCCD) for anaphylaxis (2023 version) was applied. RESULTS: The analysis included 206 participants from 13 sites: 26 participants referred for pre-vaccination assessment and 180 participants referred for adverse events following COVID-19 vaccination (15/180 [8.3%] with BCCD confirmed anaphylaxis, 84 [46.7%] with immediate hypersensitivity symptoms not meeting BCCD, 33 [18.3%] with other diagnosed hypersensitivity reactions, and 48 [26.7%] participants with a final diagnosis of non-hypersensitivity AEFI). Among participants referred for AEFIs following COVID-19 vaccination, 166/180 (92.2%) were recommended for COVID-19 revaccination after risk assessment, of whom 158/166 (95.2%) were revaccinated (all with a COVID-19 mRNA vaccine). After revaccination, 1/15 (6.7%) participants with prior anaphylaxis, 1/77 (1.3%) with immediate hypersensitivity not meeting criteria for anaphylaxis and 1/24 (4.2%) with other physician diagnosed hypersensitivity developed recurrent AEFI symptoms that met the BCCD for anaphylaxis. All 26 participants referred pre-vaccination, including 9 (34.6%) with history of polyethylene glycol-asparaginase reactions, were vaccinated without occurrence of immediate hypersensitivity symptoms. CONCLUSIONS: Most individuals in this national cohort who experienced a hypersensitivity event following COVID-19 vaccination and were referred for specialist review were revaccinated without AEFI recurrence, suggesting that specialist evaluation can facilitate safe revaccination.

Pediatric Respiratory Syncytial Virus Hospitalizations, 2017-2023.

Importance: Respiratory syncytial virus (RSV) transmission was disrupted worldwide following the COVID-19 pandemic, and further study is required to better understand these changes. Objective: To compare observed and expected RSV hospital and intensive care unit (ICU) admission rates and characteristics of admitted children during the 2021-2022 and 2022-2023 seasons. Design, Setting, and Participants: A population-based cohort study of all children aged younger than 5 years in Ontario, Canada, July 1, 2017, through March 31, 2023, was conducted. Exposures: Individual and neighborhood-level sociodemographic and clinical characteristics were identified from administrative data, including age, palivizumab eligibility, complex medical conditions, rurality, and living in a marginalized neighborhood. Main Outcomes and Measures: The main outcome was RSV-associated hospitalization. Secondary outcomes included ICU admissions, mechanical ventilation, extracorporeal membrane oxygenation, and in-hospital death. Poisson generalized estimating equations were used to model weekly age- and sex-specific hospitalization rates and estimate expected rates in the postpandemic era; adjusted rate ratios (RRs) and 95% CIs are reported. Results: This cohort study included approximately 700 000 children per study year. Compared with prepandemic years (2017-2018, 2018-2019, and 2019-2020), the 2021-2022 RSV season peaked slightly earlier, but overall admission rates were comparable (289.1 vs 281.4-334.6 per 100 000, or approximately 2000 admissions). The 2022-2023 season peaked a month earlier and resulted in more than twice as many hospitalizations (770.0 per 100 000; n = 4977 admissions). The proportion of children admitted to an ICU in 2022-2023 (13.9%) was slightly higher than prepandemic (9.6%-11.4%); however, the population-based rate was triple the prepandemic levels (106.9 vs 27.6-36.6 per 100 000 children in Ontario). With the exception of palivizumab-eligible children, all sociodemographic and health status characteristics were associated with lower-than-expected RSV hospitalization rates in 2021-2022. In contrast, older age of patients was associated with higher-than-expected rates in 2022-2023 (ie, 24-59 months: RR, 1.90; 95% CI, 1.35-2.66). Conclusions and Relevance: There were notable differences in RSV epidemiologic characteristics in Ontario following the COVID-19 pandemic. It is not yet clear whether and how long atypical RSV epidemics may persist. Clinicians and program planners should consider the potential for ongoing impacts to health care capacity and RSV immunization programs.

The Impact Of Provincial Proof- Of-Vaccination Policies On Age-Specific First-Dose Uptake Of COVID-19 Vaccines In Canada.

Requirements of proof of COVID-19 vaccination were mandated for nonessential businesses and venues by Canada's ten provinces throughout the fall of 2021. Leveraging variations in the timing of these measures across the provinces, we applied event study regression to estimate the impact the announcement of these measures had nationally on age-specific first-dose uptake in the subsequent seven-week period. Proof-of-vaccination mandate announcements were associated with a rapid, significant increase in first-dose uptake, particularly in people younger than age fifty. However, these behavioral changes were short-lived, with uptake returning to preannouncement levels-or lower-in all age groups within six weeks, despite mandates remaining in place for at least four months; this decline occurred earlier and was more apparent among adolescents ages 12-17. We estimated that nationally, 290,168 additional people received their first dose in the seven weeks after provinces announced proof-of-vaccination policies, for a 17.5 percent increase over the number of vaccinations estimated in the absence of these policies. This study provides novel age-specific evidence showing that proof-of-vaccination mandates led to an immediate, significant increase in national first-dose uptake and were particularly effective for increasing vaccination uptake in younger to middle-aged adults. Proof-of-vaccination mandates may be effective short-term policy measures for increasing population vaccination uptake, but their impact may differ across age groups.

Immunological effects and safety of live rotavirus vaccination after antenatal exposure to immunomodulatory biologic agents: a prospective cohort study from the Canadian Immunization Research Network.

BACKGROUND: People with inflammatory or autoimmune diseases are recommended to continue immunomodulatory biologic agents throughout pregnancy. However, concerns regarding potential immunosuppression in infants exposed to biologic agents have led to recommendations to avoid live vaccines in the first 6-12 months of life. We aimed to examine whether live rotavirus vaccine could be administered safely to infants exposed to biologic agents, assessed in the Canadian Special Immunization Clinic (SIC) Network. METHODS: In this prospective cohort study, infants exposed to biologic agents in utero were referred to one of six SIC sites in Canada for rotavirus vaccination recommendations. Children with other contraindications to rotavirus vaccination or older than 15 weeks were excluded. Clinical and laboratory evaluations were conducted according to a standard clinical pathway. Data were collected for relevant medical history, pregnancy outcomes, biologic agent exposure history, physical examination, laboratory results of the child, SIC recommendations for rotavirus vaccination, rotavirus vaccine series completion, and adverse events after immunisation. After parental consent, deidentified data were transferred to a central database for analysis. Children recommended for rotavirus vaccination were followed up for 8 months after series initiation to ascertain severe and serious adverse events, including severe diarrhoea, vomiting, and intussusception. FINDINGS: Between May 1, 2017, and Dec 31, 2021, 202 infants were assessed and 191 eligible infants were enrolled (97 [51%] were female and 94 [49%] were male). When including those exposed to multiple agents, the most common biologic agents to which infants were exposed were infliximab (67 [35%] of 191), adalimumab (49 [26%]), ustekinumab (18 [9%]), and vedolizumab (17 [9%]). Biologic agent exposure continued into the third trimester for 178 (93%) infants. No clinically significant abnormalities in lymphocyte subsets, quantitative immunoglobulins, or mitogen responses were detected. After SIC assessment, rotavirus vaccination was recommended for 187 (98%) of 191 infants, all of whom were followed up. By end of follow-up on Aug 19, 2022, 168 (90%) infants had initiated rotavirus vaccination; 150 (80%) completed the series. No serious adverse events after immunisation were reported, but three (2%) infants required medical attention, one for vomiting and change in stools who was subsequently diagnosed with gastroesophageal reflux disease, one for rash on labia unrelated to vaccination, and one for vomiting and diarrhoea associated with a milk allergy. INTERPRETATION: Findings from this study suggest that lymphocyte subsets and the safety of live rotavirus vaccination are generally not affected by in-utero exposure to biologic agents. Rotavirus vaccination can be offered to infants exposed to anti-TNF agents in utero. FUNDING: Public Health Agency of Canada and Canadian Institutes of Health Research through the Canadian Immunization Research Network.

Respiratory syncytial virus prevention within reach: the vaccine and monoclonal antibody landscape.

Respiratory syncytial virus is the second most common cause of infant mortality and a major cause of morbidity and mortality in older adults (aged >60 years). Efforts to develop a respiratory syncytial virus vaccine or immunoprophylaxis remain highly active. 33 respiratory syncytial virus prevention candidates are in clinical development using six different approaches: recombinant vector, subunit, particle-based, live attenuated, chimeric, and nucleic acid vaccines; and monoclonal antibodies. Nine candidates are in phase 3 clinical trials. Understanding the epitopes targeted by highly neutralising antibodies has resulted in a shift from empirical to rational and structure-based vaccine and monoclonal antibody design. An extended half-life monoclonal antibody for all infants is likely to be within 1 year of regulatory approval (from August, 2022) for high-income countries. Live-attenuated vaccines are in development for older infants (aged >6 months). Subunit vaccines are in late-stage trials for pregnant women to protect infants, whereas vector, subunit, and nucleic acid approaches are being developed for older adults. Urgent next steps include ensuring access and affordability of a respiratory syncytial virus vaccine globally. This review gives an overview of respiratory syncytial virus vaccines and monoclonal antibodies in clinical development highlighting different target populations, antigens, and trial results.

School Reopening And COVID-19 In The Community: Evidence From A Natural Experiment In Ontario, Canada.

In December 2020, Ontario, Canada, entered a provincewide shutdown to mitigate COVID-19 transmission. A regionalized approach was taken to reopen schools throughout early 2021 without any other opening of the economy, offering a unique natural experiment to estimate the impact of school reopening on community transmission. Estimated increases of 0.07, 0.08, 0.07, and 0.13 percentage points in community COVID-19 case growth rates occurred 11-15, 16-20, 21-25, and 26-30 days, respectively, after schools reopened. Although small, these changes were particularly evident among children younger than age fourteen, increased over time, and were greater when lag periods were considered, which points to a likely causal effect between in-person classes and a small increase in transmission. These findings suggest that although additional COVID-19 cases are to be expected after the reopening of schools, these risks may be manageable with sufficient, layered mitigation policies.

The federal government and Canada's COVID-19 responses: from 'we're ready, we're prepared' to 'fires are burning'.

Canada's experience with the coronavirus disease-2019 (COVID-19) pandemic has been characterized by considerable regional variation, as would be expected in a highly decentralized federation. Yet, the country has been beset by challenges, similar to many of those documented in the severe acute respiratory syndrome outbreak of 2003. Despite a high degree of pandemic preparedness, the relative success with flattening the curve during the first wave of the pandemic was not matched in much of Canada during the second wave. This paper critically reviews Canada's response to the COVID-19 pandemic with a focus on the role of the federal government in this public health emergency, considering areas within its jurisdiction (international borders), areas where an increased federal role may be warranted (long-term care), as well as its technical role in terms of generating evidence and supporting public health surveillance, and its convening role to support collaboration across the country. This accounting of the first 12 months of the pandemic highlights opportunities for a strengthened federal role in the short term, and some important lessons to be applied in preparing for future pandemics.

Challenges of using asthma admission rates as a measure of primary care quality in children: An international comparison.

OBJECTIVES: To demonstrate the challenges of interpreting cross-country comparisons of paediatric asthma hospital admission rates as an indicator of primary care quality. METHODS: We used hospital administrative data from >10 million children aged 6-15 years, resident in Austria, England, Finland, Iceland, Ontario (Canada), Sweden or Victoria (Australia) between 2008 and 2015. Asthma hospital admission and emergency department (ED) attendance rates were compared between countries using Poisson regression models, adjusted for age and sex. RESULTS: Hospital admission rates for asthma per 1000 child-years varied eight-fold across jurisdictions. Admission rates were 3.5 times higher when admissions with asthma recorded as any diagnosis were considered, compared with admissions with asthma as the primary diagnosis. Iceland had the lowest asthma admission rates; however, when ED attendance rates were considered, Sweden had the lowest rate of asthma hospital contacts. CONCLUSIONS: The large variations in childhood hospital admission rates for asthma based on the whole child population reflect differing definitions, admission thresholds and underlying disease prevalence rather than primary care quality. Asthma hospital admissions among children diagnosed with asthma is a more meaningful indicator for inter-country comparisons of primary care quality.

Family and Child Risk Factors for Early-Life RSV Illness.

BACKGROUND AND OBJECTIVES: Most infants hospitalized with respiratory syncytial virus (RSV) do not meet common "high-risk" criteria and are otherwise healthy. The objective of this study was to quantify the risks and relative importance of socioeconomic factors for severe, early-life RSV-related illness. We hypothesized several of these factors, particularly those indicating severe social vulnerability, would have statistically significant associations with increased RSV hospitalization rates and may offer impactful targets for population-based RSV prevention strategies, such as prophylaxis programs. METHODS: We used linked health, laboratory, and sociodemographic administrative data for all children born in Ontario (2012-2018) to identify all RSV-related hospitalizations occurring before the third birthday or end of follow-up (March 31, 2019). We estimated rate ratios and population attributable fractions using a fully adjusted model. RESULTS: A total of 11 782 RSV-related hospitalizations were identified among 789 484 children. Multiple socioeconomic factors were independently associated with increased RSV-related admissions, including young maternal age, maternal criminal involvement, and maternal history of serious mental health and/or addiction concerns. For example, an estimated 4.1% (95% confidence interval: 2.2 to 5.9) of RSV-related admissions could be prevented by eliminating the increased admissions risks among children whose mothers used welfare-based drug insurance. Notably, 41.6% (95% confidence interval: 39.6 to 43.5) of admissions may be prevented by targeting older siblings (eg, through vaccination). CONCLUSIONS: Many social factors were independently associated with early-life RSV-related hospitalization. Existing RSV prophylaxis and emerging vaccination programs should consider the importance of both clinical and social risk factors when determining eligibility and promoting compliance.

Community-Based Antibiotic Prescribing Attributable to Respiratory Syncytial Virus and Other Common Respiratory Viruses in Young Children: A Population-Based Time-series Study of Scottish Children.

BACKGROUND: Inappropriate antibiotic prescribing, such as for viral illness, remains common in primary care. The objective of this study was to estimate the proportion of community-prescribed antibiotics to children aged less than 5 years attributable to common respiratory viruses. METHODS: We fitted time-series negative binomial models to predict weekly antibiotic prescribing rates from positive viral pathogen tests for the period 1 April 2009 through 27 December 2017 using comprehensive, population-based administrative data for all children (<5 years) living in Scotland. Multiple respiratory viral pathogens were considered, including respiratory syncytial virus (RSV), influenza, human metapneumovirus (HMPV), rhinovirus, and human parainfluenza (HPIV) types 1-4. We estimated the proportion of antibiotic prescriptions explained by virus circulation according to type of virus, by age group, presence of high-risk chronic conditions, and antibiotic class. RESULTS: We included data on 6 066 492 antibiotic prescriptions among 452 877 children. The antibiotic-prescribing rate among all Scottish children (<5 years) was 609.7 per 1000 child-years. Our final model included RSV, influenza, HMPV, HPIV-1, and HPIV-3. An estimated 6.9% (95% confidence interval, 5.6-8.3%), 2.4% (1.7-3.1%), and 2.3% (.8-3.9%) of antibiotics were attributable to RSV, influenza, and HMPV, respectively. RSV was consistently associated with the highest proportion of prescribed antibiotics, particularly among children without chronic conditions and for amoxicillin and macrolide prescriptions. CONCLUSIONS: Nearly 14% of antibiotics prescribed to children in this study were estimated to be attributable to common viruses for which antibiotics are not recommended. A future RSV vaccine could substantially reduce unnecessary antibiotic prescribing among children.

Palivizumab's real-world effectiveness: a population-based study in Ontario, Canada, 1993-2017.

OBJECTIVE: To evaluate the effectiveness of two palivizumab programmes targeting high-risk infants, defined by prematurity, diagnosis of comorbidities and geography, and assess potential disparities by neighbourhood income. DESIGN: Controlled, interrupted time series. SETTING: Ontario, Canada. PATIENTS: We used linked health and demographic administrative databases to identify all children born in hospitals 1 January 1993 through 31 December 2016. Follow-up ended at the earliest of second birthday or 30 June 2017. INTERVENTION: Palivizumab-eligibility: child was born very preterm and ≤6 months old during respiratory syncytial virus (RSV) season; <24 months old with significant chronic lung or congenital heart disease; or ≤6 months, born preterm or residents of remote regions. MAIN OUTCOME: Severe RSV-related illness, defined as hospitalisation or death with a diagnosis of bronchiolitis, RSV pneumonia or RSV. RESULTS: 3 million births and 87 000 RSV-related events were identified. Over the study period, rates of severe RSV-related illness declined 65.4% among the highest risk group, eligible infants <6 months (230.6 to 79.8 admissions per 1000 child-years). Relative to changes among ineligible infants <6 months, rates dropped 10.4% (95% CI -18.6% to 39.4%) among eligible infants immediately following introduction of a national palivizumab programme in 1998. Initially, rates were considerably higher among infants from low-income neighbourhoods, but income-specific rates converged over time among eligible infants <6 months; such convergence was not seen among other children. CONCLUSIONS: Incidence of severe RSV-related illness declined over the study period. While we cannot attribute causality, the timing and magnitude of these declines suggest impact of palivizumab in reducing RSV burden and diminishing social inequities among palivizumab-eligible infants.

Development and validation of a simple algorithm to estimate common gestational age categories using standard administrative birth record data in Ontario, Canada.

Gestational age is often incompletely recorded in administrative records, despite being critical to paediatric and maternal health research. Several algorithms exist to estimate gestational age using administrative databases; however, many have not been validated or use complicated methods that are not readily adaptable. We developed a simple algorithm to estimate common gestational age categories from routine administrative data. We leveraged a population-based registry of all hospital births occurring in Ontario, Canada over 2002-2016 including 1.8 million birth records. In this sample, this simple algorithm had excellent performance compared to a verified measure of gestational age; 87.61% agreement (95% CI: 87.49, 87.74). The accuracy of the algorithm exceeded 98% for all of the gestational age categories. Agreement notably increased over time and was greatest among singleton births and infants born at 2500-2999 g. This study provides a straight-forward algorithm for accurately estimating common gestational age categories that is easily adaptable for use in other countries.Impact StatementWhat is already known on this subject? Gestational age is often incompletely or inaccurately recorded in administrative health databases, despite being critical to the study of many paediatric and maternal health outcomes. Consequently, researchers must rely on various methods to estimate gestational age, many of these methods are either overly simple (i.e. assuming a uniform duration) or analytically complicated and difficult to adapt for new populations (e.g. regression-based approaches).What the results of this study add? This study, based on a population-based registry of all 1.8 million births occurring in Ontario, Canada 2003-2016, found that a simple, sex-specific algorithm using three commonly recorded birth record characteristics performs almost perfectly compared to a clinical estimate recorded near birth.What the implications are of these findings for clinical practice and/or further research? This study suggests that a straight-forward, sex-specific algorithm based on routinely collected birth record data is able to accurately estimate common gestational age categories (i.e. extreme preterm, <28 weeks; very preterm, 28-32 weeks; moderate-to-late preterm, 33-26 weeks; and term, 37 weeks of completed gestational age). This work will be of greatest interest to perinatal researchers using routinely collected health administrative data.

Deprivation and mortality related to pediatric respiratory tract infection: a cohort study in 3 high-income jurisdictions.

BACKGROUND: Deaths from respiratory tract infections (RTIs) in children are preventable through timely access to public health and medical interventions. We aimed to assess whether socioeconomic disparities in mortality related to pediatric RTI persisted after accounting for health status at birth. METHODS: We compared the prevalence of and risk factors for RTI-related death in singletons aged 28 days to 4 years across Ontario (Canada), Scotland and England (jurisdictions with universal health care) using linked administrative data for 2003-2013. We estimated rates of RTI-related mortality for children living in deprived areas and those born to teenage girls; we estimated both crude rates and those adjusted for health status at birth. RESULTS: A total of 1 299 240 (Ontario), 547 556 (Scotland) and 3 910 401 (England) children were included in the study. Across all jurisdictions, children born in the most deprived areas experienced the highest rates of RTI-related mortality. After adjustment for high-risk chronic conditions and prematurity, we observed differences in mortality according to area-level deprivation in Ontario and England but not in Scotland. In Ontario, teenage motherhood was also an independent risk factor for RTI-related mortality. INTERPRETATION: Socioeconomic disparities played a substantial role in child mortality related to RTI in all 3 jurisdictions. Context-specific investigations around the mechanisms of this increased risk and development of programs to address socioeconomic disparities are needed.

Vancomycin-resistant enterococci (VRE) screening and isolation in the general medicine ward: a cost-effectiveness analysis.

Background: Vancomycin-resistant enterococci (VRE) are a serious antimicrobial resistant threat in the healthcare setting. We assessed the cost-effectiveness of VRE screening and isolation for patients at high-risk for colonisation on a general medicine ward compared to no VRE screening and isolation from the healthcare payer perspective. Methods: We developed a microsimulation model using local data and VRE literature, to simulate a 20-bed general medicine ward at a tertiary-care hospital with up to 1000 admissions, approximating 1 year. Primary outcomes were accrued over the patient's lifetime, discounted at 1.5%, and included expected health outcomes (VRE colonisations, VRE infections, VRE-related bacteremia, and deaths subsequent to VRE infection), quality-adjusted life years (QALYs), healthcare costs, and incremental cost-effectiveness ratio (ICER). Probabilistic sensitivity analysis (PSA) and scenario analyses were conducted to assess parameter uncertainty. Results: In our base-case analysis, VRE screening and isolation prevented six healthcare-associated VRE colonisations per 1000 admissions (6/1000), 0.6/1000 VRE-related infections, 0.2/1000 VRE-related bacteremia, and 0.1/1000 deaths subsequent to VRE infection. VRE screening and isolation accrued 0.0142 incremental QALYs at an incremental cost of $112, affording an ICER of $7850 per QALY. VRE screening and isolation practice was more likely to be cost-effective (> 50%) at a cost-effectiveness threshold of $50,000/QALY. Stochasticity (randomness) had a significant impact on the cost-effectiveness. Conclusion: VRE screening and isolation can be cost-effective in majority of model simulations at commonly used cost-effectiveness thresholds, and is likely economically attractive in general medicine settings. Our findings strengthen the understanding of VRE prevention strategies and are of importance to hospital program planners and infection prevention and control.

Assessment of Long-term Follow-up of Randomized Trial Participants by Linkage to Routinely Collected Data: A Scoping Review and Analysis.

Importance: Follow-up of participants in randomized trials may be limited by logistic and financial factors. Some important randomized trials have been extended well beyond their original follow-up period by linkage of individual participant information to routinely collected data held in administrative records and registries. Objective: To perform a scoping review of randomized clinical trials extended by record linkage to characterize this literature and explore any additional insights into treatment effectiveness provided by long-term follow-up using record linkage. Data Sources: A literature search in Embase, CINAHL, MEDLINE, and the Cochrane Register of Controlled Trials was performed for the period January 1, 1945, through November 25, 2016. Study Selection: Various combinations of search terms were used, as there is no accepted terminology. Determination of study eligibility and extraction of information about trial characteristics and outcomes, for both original and extended trial reports, were performed in duplicate. Data Extraction and Synthesis: Assessment of study eligibility and data extraction were performed independently by 2 reviewers. All analyses were descriptive. Main Outcomes and Measures: Outcomes in the pairs of original and extended trials were categorized according to whether any benefits or harms from interventions were sustained, were lost, or emerged during long-term follow-up. Results: A total of 113 extended trials were included in the study. Linkage to administrative and registry data extended follow-up by between 1 and 55 years. The most common interventions were pharmaceuticals (47 [41.6%]), surgery (19 [16.8%]), and disease screening (19 [16.8%]). End points most frequently studied through record linkage included mortality (88 [77.9%]), cancer (41 [36.3%]), and cardiovascular events (37 [32.7%]). One hundred four trial extensions (92.0%) were analyzed according to the original trial randomization. The reports provided details of 155 analyses of study outcomes. Seventy-four analyses (47.7%) identified statistically significant benefits in the trial extension phase. In 21 of these (28.4%), benefits were significant only in this period. Null results in both the original and extended trials were seen in 34 of the analyses (21.9%). Loss of significant benefits of an intervention were seen in 12 analyses (7.7%). Statistically significant harms were seen in 16 trial extension analyses (10.3%), and in 14 of these (87.5%), the harms were significant only in the trial extension phase. Conclusions and Relevance: Trial extension by linkage to routinely collected data is a versatile underused approach that may add critical insights beyond those of the original trial. Some beneficial and harmful outcomes of interventions are captured only in the extension phase of randomized trials.