Canadian Medical Association Journal

IntroductionNational responses to the SARS-CoV-2 pandemic have been highly variable, which may explain some of the heterogeneity in the pandemics health and economic impacts across the world. We sought to explore the effectiveness of the Canadian pandemic response relative to responses in four peer countries with similar political, economic and health systems, and with close historical and cultural ties to Canada (the United States, United Kingdom, France, and Australia) from March 2020 to May 2022. MethodsWe used reported age-specific mortality data to generate estimates of pandemic mortality standardized to the Canadian population. Age-specific case fatality, hospitalization, and intensive care admission probabilities for the Canadian province of Ontario were applied to estimated deaths in order to calculate hospitalizations and intensive care admissions averted by the Canadian response. The monetary value of averted hospitalizations was estimated using cost estimates from the Canadian Institute for Health Information. Age-specific quality-adjusted life-years (QALY) lost due to fatality were estimated using published estimates. QALY were monetized using a net expected benefit approach. ResultsRelative to the United States, United Kingdom, and France, the Canadian pandemic response was estimated to have averted 94,492, 64,306 and 13,641 deaths respectively, with more than 480,000 hospitalizations averted, and 1 million QALY saved, relative to the United States. A United States pandemic response applied to Canada would have resulted in more than $40 billion in economic losses due to healthcare expenditures and lost QALY; losses relative to the United Kingdom and France would have been $21 billion and $5 billion respectively. By contrast, an Australian pandemic response would have averted over 28,000 additional deaths and averted nearly $9 billion in costs in Canada. ConclusionsCanada outperformed peer countries that aimed for mitigation, rather than elimination, of SARS-CoV-2 in the first two years of the pandemic, likely because of a more stringent public health response to disease transmission. This resulted in substantial numbers of lives saved and economic costs averted. However, comparison with Australia demonstrates that an elimination focus would have allowed Canada to save tens of thousands of lives, and would have saved substantial economic costs.

ObjectiveThe aim of this study was to describe differences and trends in ATV-related hospitalizations for urban and rural-dwelling youth in Canada. MethodsWe conducted a cross-sectional study using administrative hospital abstract data all patients admitted for an ATV-related injury to hospitals in 9 provinces in Canada between 2002 and 2019. The primary exposure was rural residence, defined by postal code. Rural-urban comparisons were stratified by age group: children (<16 years), adolescents (16-20 years) and adults (>21 years). The primary outcome was the incidence of any hospitalization, secondary outcomes were head injury, fractures, crush injury and spinal cord injury.. ResultsAmong 34,390 patients with complete data, 17% were children younger than 16 yrs and 14% were adolescents 16-20 yrs; 78% of children and 85% of adolescents were male, and 47% lived rurally. The incident rate ratio (IRR) for being hospitalized for an ATV-related injury was 5-fold higher for rural children (5.59; 95% CI: 5.30-5.88) and adolescents (5.16; 95% CI: 4.88, 5.47) compared to urban children and adolescents, respectively. The 5-fold higher IRR was also evident for ATV-related fractures among rural children and adolescents. Adolescents had a particularly higher risk for ATV-related crush injuries (IRR: 10.43; 95% CI: 5.74-18.96) and spinal cord injuries (IRR: 5.21; 95% CI: 3.33-8.15) while children were at higher risk of ATV-related head injuries (IRR: 6.55; 95% CI: 5.76-7.46) compared to urban dwelling youth. ConclusionsIn Canada, rural children and adolescents were at a very elevated risk of ATV injuries compared to those living in urban centres.

SARS-CoV-2 strained Ontarios health system, with social determinants of health (SDH) underexplored in cost analyses. We examined COVID-19 attributable healthcare resource use and costs from the Ontario health system perspective using health administrative data. We conducted a cohort study, matching 162,633 SARS-CoV-2-exposed individuals 1:1 to unexposed individuals. We calculated 10-day per-person mean attributable costs (2023 CAD) across care phases (pre-diagnosis, acute, post-acute, terminal), stratified by individual and area-level SDH. Among exposed individuals (mean age 40.4 years, 50.7% female), 6% were hospitalized, 1.3% admitted to critical care, and 2% died within 360 days. Mean (SD) person acute phase cost was $244 ($235-$253) and higher among males, recent immigrants, individuals living in low-income neighbourhoods and neighbourhoods with a higher proportion of crowded households. Extrapolating to the population level of 166,801 exposed individuals, the mean total survival-adjusted 360-day cost was $436 million. COVID-19 increased healthcare costs, disproportionately burdening marginalized communities.

BackgroundIn central Ontario, influenza, respiratory syncytial virus (RSV), and invasive pneumococcal disease (IPD) follow similar seasonal patterns, peaking in winter. We aimed to quantify the independent and joint impact of influenza A, influenza B, and RSV on IPD risk at the population level. MethodsWe used a 2:1 self-matched case-crossover study design to evaluate acute effects of respiratory virus activity on IPD risk. This design ensures that effects are not confounded by within-individual characteristics that remain constant over short periods of time. We included 3,892 IPD cases occurring between January 2000 and June 2009. Effects were measured using univariable and multivariable conditional logistic regression. Multivariable models included environmental covariates (e.g., temperature, absolute humidity, and UV index) and interaction terms between viruses. ResultsInfluenza A activity and influenza B activity were both independently associated with increased IPD risk; however, co-circulation of influenza A and B reduced the impact of both viruses. RSV activity was positively associated with increased IPD risk only in the presence of increased influenza A or influenza B activity. ConclusionsTo our knowledge this represents the first study to consider the impact of interactions between these viruses on IPD risk in Canada. Our findings suggest that the prevention of IPD should be considered as a potential health benefit of influenza and RSV vaccination programs.

BackgroundThe requirement for critical care in even a modest fraction of SARS-CoV-2 infected individuals made ICU resources an important societal chokepoint during the recent pandemic. We developed a simple regression-based point score in 2020 based on an objective of forecasting critical care occupancy in the Canadian province of Ontario based on mean age of cases, case numbers, and testing volume. Evolution of the pandemic (variants of concern, vaccination) led us to re-assess and re-calibrate our earlier work, with inclusion of information vaccination which became widespread in 2021. MethodsWe obtained complete provincial SARS-CoV-2 case, testing, and vaccination data for the period from March 2020 to September 2022, with data subdivided into 6 major "waves", following the approach applied by other Canadian investigators. Our initial model was fit only using the first two "wild type" SARS-CoV-2 waves; an updated model included wave 3 (N501Y+ variants). Our model was validated by comparing model projections to waves not used for model fitting; validation model fits were evaluated with Spearmans rho; counterfactuals without vaccination were modeled to impute fraction of critical care admissions prevented with vaccination. Costing was based on published economic estimates. ResultsOur initial model (fit to waves 1 and 2) was well calibrated (rho 0.85) but predictive validity was modest (rho 0.46). Predictive validity improved in models fit to the first 3 pandemic waves without vaccination (rho 0.60) or with vaccination (rho 0.68) (P for inclusion of vaccination 0.013 by Likelihood Ratio Test). Prevented fraction of ICU admissions attributable to vaccination was 144% (22017 admissions expected vs. 9020 observed); based on published estimates of ICU admission cost for SARS-CoV-2 the 12977 admissions averted $2.9 (CDN) billion in economic costs, in contrast to the $3 billion total cost of the vaccination program. ConclusionsSimple time series regression incorporating case and testing characteristics continues to be useful as a tool for forecasting critical care occupancy due to SARS-CoV-2 but early pandemic models need to be updated to capture the preventive effects of widespread vaccination. The economic benefit of vaccination for prevention of critical care resource consumption during the pandemic is substantial, achieving near cost neutrality with the provinces entire vaccination program.

ObjectiveTo estimate costs, quality-adjusted life-years, and the value of undertaking a future randomized controlled trial for different oxygenation thresholds used to initiate invasive ventilation in hypoxemic respiratory failure. DesignModel-based cost-utility estimation with individual-level simulation and value-of-information analysis. SettingCritical care units. ParticipantsAdults admitted to critical care receiving non-invasive oxygen. InterventionsWe compared four strategies: initiation of invasive ventilation at thresholds of saturation-to-inspired oxygen fraction ratio (SF) < 110, < 98, or < 88, and usual care. Main resultsAn invasive ventilation initiation threshold of SF < 110, compared to usual care, resulted in more predicted invasive ventilation (62% vs 31%), hospital survival (78.4% vs 75.5%), quality-adjusted life years (QALYs) (8.48 vs 8.34), and lifetime costs (86,700 Canadian dollars (CAD) vs 75,600 CAD). Among the four strategies, threshold SF < 110 had the highest expected net monetary benefit (761,000 CAD), but there was significant uncertainty, because all four strategies had similar probability (range: 23.5% to 27.5%) of having the best net monetary benefit. The expected value to society over the next 10 years of a 400-person randomized trial of oxygenation thresholds was 4.27 billion CAD, and remained high (2.64 billion CAD) in a scenario analysis considering a hypothetical threshold that resulted in less invasive ventilation and similar survival compared to usual care. ConclusionThe preferred threshold to initiate invasive ventilation in hypoxemic respiratory failure is uncertain. It would be highly valuable to society to identify thresholds that, in comparison to usual care, either improve survival or reduce invasive ventilation without reducing survival. Key points QuestionWhat are the costs and quality-adjusted life-years associated with different oxygenation thresholds for initiating invasive ventilation, and what is the expected value to society of a randomized controlled trial? FindingsIn this health economic evaluation comparing usual care to three different thresholds for initiating invasive ventilation in hypoxemic respiratory failure based on the saturation-to-inspired oxygen fraction ratio (SF), we found that threshold SF < 110 had the highest expected quality-adjusted life-years and net monetary benefit, despite increased predicted invasive ventilation use. However, there was significant residual uncertainty, and the expected value to society of a 400-person randomized trial to compare thresholds for initiating invasive ventilation was greater than 2.5 billion Canadian dollars. MeaningThe preferred threshold to initiate invasive ventilation in hypoxemic respiratory failure is uncertain and further study would be valuable to society. Social media summaryWhen should we intubate and start invasive ventilation for people with hypoxemic respiratory failure? Our health economic evaluation shows that the preferred threshold is uncertain, but that a clinical trial to determine such a threshold would be immensely valuable to patients and society

The pandemic caused by SARS-CoV-2 has proven challenging clinically, and at the population level, due to heterogeneity in both transmissibility and severity. Recent case incidence in Ontario, Canada (autumn 2020) has outstripped incidence in seen during the first (spring) pandemic wave; but has been associated with a lower incidence of intensive care unit (ICU) admissions and deaths. We hypothesized that differential ICU burden might be explained by increased testing volumes, as well as the shift in mean case age from older to younger. We constructed a negative binomial regression model using only three covariates, at a 2-week lag: log10(weekly cases); log10(weekly deaths); and mean weekly case age. This model reproduced observed ICU admission volumes, and demonstrated good preliminary predictive validity. Furthermore, when admissions were used in combination with ICU length of stay, our modeled estimates demonstrated excellent convergent validity with ICU occupancy data reported by the Canadian Institute for Health Information. Our approach needs external validation in other settings and at larger and smaller geographic scales, but appears to be a useful short-term forecasting tool for ICU resource demand; we also demonstrate that the virulence of SARS-CoV-2 infection has not meaningfully changed in Ontario between the first and second waves, but the demographics of those infected, and the fraction of cases identified, have.

BackgroundSARS-CoV-2 is a novel pandemic pathogen that displays great variability in virulence across cases. Due to limitations in diagnostic testing only a subset of infections are identified. Underestimation of true infections makes calculation of infection fatality ratios (IFR) challenging. Seroepidemiology allows estimation of true cumulative incidence of infection in populations, for estimation of IFR. MethodsSeroprevalence estimates were derived using retention samples stored by Canadian Blood Services in May 2020. These were compared to non-long-term care-linked case and fatality data from the same period. Estimates were combined to generate IFR and case identification fraction estimates. ResultsOverall IFR was estimated to be 0.80% (0.75 to 0.85%), consistent with estimates from other jurisdictions. IFR increased exponentially with age from 0.01% (0.002 to 0.04%) in those aged 20-29 years, to 12.71% (4.43 to 36.50%) in those aged 70 and over. We estimated that 5.88 infections (3.70 to 9.21) occurred for every case identified, with a higher fraction of cases identified in those aged 70 and older (42.0%) than those aged 20-29 (9.4%). IFR estimates in those aged 60 and older were identical to pooled estimates from other countries. ConclusionsTo our knowledge these are the first Canadian estimates SARS-CoV-2 IFR and case identification fraction. Notwithstanding biases associated with donor sera they are similar to estimates from other countries, and approximately 80-fold higher than estimates for influenza A (H1N1) during the 2009 epidemic. Ontarios first COVID-19 pandemic wave is likely to have been accurately characterized due to a high case identification fraction.

As the COVID-19 pandemic has progressed, more local data has become available, enabling a more granular modeling approach. In March 2020, we developed a COVID-19 Resource Estimator (CORE) model to estimate the acute care resource use in Ontario, Canada. In this paper, we describe the evolution of CORE2.0 to incorporate age, sex, and time-dependent acute care resource use, length of stay, and mortality to simulate hospital occupancy. Demographics (e.g., age and sex) of infected cases are informed by 4-month averages between March-June, and July-October using 10-year age groups. The probability of hospitalization, ICU admission, and requiring mechanical ventilation are all age and sex-dependent. LOS for each acute care level ranges from 5.7 to 16.15 days in the ward, 6.5 to 10.7 days in the ICU without ventilation, and 14.8 to 21.6 days on the ventilator, depending on month of infection. We calibrated some LOS components to reported ward and ICU occupancy between June 15 and October 31, 2020. Furthermore, we demonstrate the use of CORE2.0 for a regional analysis of Region of Waterloo, Ontario, Canada to simulate the ward bed, ICU bed, and ventilator occupancies for 30 days starting December 2020 for three case trajectory scenarios. Moving forward, this model has become highly flexible and customizable to data updates, and can better inform acute care planning and public measures as the pandemic progresses.

Case-based tracking of COVID-19 in children and adolescents may underestimate infection, and compared with adults there is little pediatric SARS-CoV-2 seroprevalence data. To assess evidence of previous SARS-CoV-2 infections among children and adolescents in Mississippi, serologic testing for antibodies to SARS-CoV-2 was conducted on a convenience sample of residual serum specimens collected for routine laboratory testing by an academic medical center laboratory during May 17 through September 19, 2020. Seroprevalence by calendar month was standardized to the state population by race/ethnicity; cumulative numbers of infections were estimated by extrapolating seroprevalence to all those aged <18 years in Mississippi. Serum specimens from 1,603 individuals were tested; 175 (10.9%) were positive for SARS-CoV-2 antibodies. Among 1,579 (98.5%) individuals for whom race/ethnicity was known, the number testing positive was 16 (23.2%) of 69 Hispanic individuals, 117 (13.0%) of 901 non-Hispanic Black individuals and 30 (5.3%) of 565 non-Hispanic White individuals. Population-weighted seroprevalence estimates among those aged <18 years increased from 2.6% in May to 16.9% in September 2020. Cumulative numbers of infections extrapolated from seroprevalence data, however, were estimated at 117,805 (95% confidence interval [CI] = 68,771-168,708), suggesting that cases in children and adolescents are much higher than what was reported to the Mississippi State Department of Health (9,044 cases during this period). Further data to appreciate the burden of pediatric disease to inform public health policy is urgently needed.

ObjectivesEstimates of health system costs due to COVID-19, especially for long-term disability (post COVID-19 condition [PCC]) are key to health system planning, but attributable cost data remain scarce. We characterized COVID-19-attributable costs from the health system perspective. MethodsPopulation-based matched cohort study in Ontario, Canada, using health administrative data. To assign attribution to COVID-19, individuals, defined as exposed (positive SARS-CoV-2 PCR test, 01/2020-12/2020) were matched 1:1 to an unexposed individuals (01/2016-12/2018). Historical matching was used to reduce biases due to overall reductions in healthcare during the pandemic and contamination bias. The index date was defined as the first occurrence of positive SARS-CoV-2 PCR test. We used phase-of-care costing to calculate mean attributable per-person costs (2023 CAD), standardized to 10 days, during four phases of illness: pre-index date, acute care, post-acute care (suggestive of PCC), and terminal phase (stratified by early and late deaths). Finally, we estimated total costs at 360 days by combining costs with survival estimates. ResultsOf 165,838 exposed individuals, 159,817 were matched (mean age 40{+/-}20 years, 51% female). Mean (95%CI) attributable 10-day costs per person were $1 ($-4, $6) pre-index, $240 ($231, $249) during acute care, and $18 ($14, $21) during post-acute phases. During the terminal phase, mean attributable costs were $3,928 ($3,471, $4,384) for early deaths and $1,781 ($1,182, $2,380) for late deaths. Hospitalizations accounted for 42% to 100% of total costs. Compared to males, costs among females were lower during the acute care phase, but higher during the post-acute care phase. Mean cumulative per-person cost at 360 days was $2,553 ($2,348, $2,756); females had lower costs ($2,194 [$1,945, $2,446]) than males ($2,921 [$2,602, $3,241]). ConclusionsSARS-CoV-2 infection is associated with substantial long-term healthcare costs, consistent with our understanding of the PCC. Understanding phase-specific costs can inform health sector budget planning, future economic evaluations, and pandemic planning.

BackgroundRespiratory viruses are major contributors to population mortality, but cause-of-death coding undercounts their impact. Ecological regression models linking viral circulation to mortality fluctuations can address this limitation. AimTo estimate the population attributable fraction (PAF) of mortality associated with influenza A and B, respiratory syncytial virus (RSV), and SARS-CoV-2 in Ontario, Canada (1993-2025), and to characterize temporal changes in virus-attributable mortality across the pandemic transition. MethodsWe analysed monthly all-cause mortality data with laboratory surveillance indicators for influenza A, B, RSV, and SARS-CoV-2. Negative binomial models with secular trends, Fourier seasonal terms, and population offsets were fit for pre-pandemic (January 1993-February 2020) and combined pandemic (March 2020-February 2025) periods. PAFs were derived from counterfactual predictions setting viral coefficients to zero. Sensitivity analyses examined temporal stratification of the pandemic period (Public Health Emergency of International Concern [PHEIC] period: March 2020-April 2023; post-PHEIC: May 2023-February 2025), exclusion of the early pandemic period (March-June 2020), and models without Fourier seasonal adjustment. Wald tests compared coefficients across specifications. ResultsPre-pandemic, influenza A accounted for 1.8% (95% CI 1.4-2.3%) of mortality; influenza B showed no detectable impact. RSV demonstrated inverse associations in seasonally adjusted models but positive associations (PAF 1.9%, 95% CI 1.3-2.4%) without seasonal adjustment. Over the combined pandemic period (March 2020-February 2025; n=60 months), amid elevated baseline mortality (IRR 1.050, P=0.027), SARS-CoV-2 accounted for 6.1% (95% CI 4.2-8.0%) of deaths, approximately 4-fold the pre-pandemic influenza A burden, despite widespread vaccination and antiviral availability. Model-estimated SARS-CoV-2-attributable deaths closely matched reported COVID-19 deaths from Public Health Ontario over the same period. Temporal stratification identified a significant increase in SARS-CoV-2-attributable mortality in the post-PHEIC period (PAF 9.8%, 95% CI 1.1-17.7%; p=0.027), while post-PHEIC influenza A and B attributable fractions did not differ significantly from pre-pandemic baselines. Excluding March-June 2020 yielded a conservative SARS-CoV-2 PAF of 5.7% (95% CI 3.3-8.1%), confirming robustness of primary estimates. Meta-analyses showed substantial heterogeneity for influenza A (I{superscript 2}=92.8%) and RSV (I{superscript 2}=89.1%) across modeling approaches, but minimal heterogeneity for SARS-CoV-2 (I{superscript 2}=5.5%). ConclusionSARS-CoV-2 was associated with a 3-4-fold higher population mortality burden than seasonal influenza A despite available countermeasures. Post-PHEIC data suggest that the burden of respiratory virus mortality, including for influenza, has not returned to pre-pandemic levels, highlighting the continued importance of respiratory virus prevention strategies. Estimates for influenza A and RSV were sensitive to seasonal adjustment, highlighting the importance of modelling choices when quantifying virus-attributable mortality.

BackgroundEmpirical evidence on the indirect herd benefits of COVID-19 vaccination and/or prior infection is limited. We aimed to examine how area-level immunity interacts with individual-level immunity to affect COVID-19 diagnoses and deaths. MethodsOntario residents aged [&ge;]18 years were followed from August-01-2021 to January-30-2022. Individual-level immunity was defined as received a primary series of COVID-19 vaccines or a positive SARS-CoV-2 test in the past 165 days. Area-level immunity was determined based on the proportion of immune individuals in an individuals residing area. We used logistic regression and cause-specific hazard models to examine the relationship between immunity and COVID-19 diagnosis, and between immunity and COVID-19 death, respectively. We included an interaction term between individual-level and area-level immunity in each model. ResultsOf 11,122,816 adults, 7,518,015 (67.6%) were immune at baseline. After accounting for individual-level demographics, baseline health, and area-level social determinants of health, area-level immunity (highest vs. lowest quintiles) was associated with lower odds of COVID-19 diagnosis; the association was larger among non-immune (odds ratios [95% confidence interval]: 0.72 [0.70, 0.75]) than immune individuals (0.93 [0.90, 0.96]). Higher area-level immunity (highest vs. lowest quintiles) was also associated with lower hazard of COVID-19 death among non-immune individuals (hazard ratio: 0.77 [0.60, 1.00]). ConclusionsOur study provides observational evidence supporting the herd benefits of vaccination or prior infection on SARS-CoV-2 infections and COVID-19 deaths. Findings reinforce the need for high vaccination coverage to protect vaccinated and unvaccinated populations, while providing insights for interpreting vaccine effectiveness estimates in the context of herd immunity. Main pointsUsing area-level immunity coverage as a proxy for herd immunity, our study demonstrates observational evidence of indirect herd benefits from vaccination and/or prior infection on SARS-CoV-2 infections and COVID-19 deaths. Moreover, herd benefits are greater among non-immune individuals.

Acute Kidney Injury (AKI) is among the most common complications of Coronavirus Disease 2019 (COVID-19). Throughout 2020 pandemic, the clinical approach to COVID-19 has progressively improved, but it is unknown how these changes have affected AKI incidence and severity. In this retrospective analysis, we report the trend over time of COVID-19 associated AKI and need of renal replacement therapy in a large health system in New York City, the first COVID-19 epicenter in United States.

Introduction - Worldwide, nursing home residents have experienced disproportionately high COVID-19 mortality due to the intersection of congregate living, multimorbidity, and advanced age. Among 12 OECD countries, Canada has had the highest proportion of COVID-19 deaths in nursing home residents (78%), raising concerns about a skewed pandemic response that averted much transmission and mortality in community-dwelling residents, but did not adequately protect those in nursing homes. To investigate this, we measured temporal variations in hospitalizations among community and nursing home-dwelling decedents with COVID-19 during the first and second waves of the pandemic. Methods - We conducted a population-based cohort study of residents of Ontario, Canada with COVID-19 who died between March 11, 2020 (first COVID-19 death in Ontario) and October 28, 2020. We examined hospitalization prior to death as a function of 4 factors: community (defined as all non-nursing home residents) vs. nursing home residence, age in years (<70, 70-79, 80-89, [&ge;]90), gender, and month of death (1st wave: March-April [peak], May, June-July 2020 [nadir], 2nd wave: August-October 2020). Results - A total of 3,114 people with confirmed COVID-19 died in Ontario from March to October, 2020 (Table 1), of whom 1,354 (43.5%) were hospitalized prior to death (median: 9 days before death, interquartile range: 4-19). Among nursing home decedents (N=2000), 22.4% were admitted to hospital prior to death, but this varied substantially from a low of 15.5% in March-April (peak of wave 1) to a high of 41.2% in June-July (nadir of wave 1). Among community-dwelling decedents (N=1,114), admission to acute care was higher (81.4%) and remained relatively stable throughout the first and second waves. Similar temporal trends for nursing home versus community decedents were apparent in age-stratified analyses (Figure 1). Women who died were less likely to have been hospitalized compared to men in both community (80% women vs 84% men) and nursing home (21% women vs 24% men) settings. Discussion - Only a minority of Ontario nursing home residents who died of COVID-19 were hospitalized prior to death, and that there were substantial temporal variations, with hospitalizations reaching their lowest point when overall COVID-19 incidence peaked in mid-April, 2020. While many nursing home residents had pre-pandemic advance directives precluding hospitalization, the low admission rate observed in March-April 2020 (15.5%) was inconsistent with both higher admission rates in subsequent months (>30%), and comparatively stable rates among community-dwelling adults. Our findings substantiate reports suggesting that hospitalizations for nursing home residents with COVID-19 were low during the peak of the pandemics first wave in Canada, which may have contributed to the particularly high concentration of COVID-19 mortality in Ontarios nursing homes.

BackgroundProvision of safe and effective vaccines has been a remarkable public health achievement during the SARS-CoV-2 pandemic. The effectiveness and durability of protection of the first two doses of SARS-CoV-2 vaccines is an important area for study, as are questions related to optimal dose combinations and dosing intervals. MethodsWe performed a case-cohort study to generate real-world evidence on efficacy of first and second dose of SARS-CoV-2 vaccines, using a population-based case line list and vaccination database for the province of Ontario, Canada between December 2020 and October 2021. Risk of infection after vaccination was evaluated in all laboratory-confirmed vaccinated SARS-CoV-2 cases, and a 2% sample of vaccinated controls, evaluated using survival analytic methods, including construction of Cox proportional hazards models. Vaccination status was treated as a time-varying covariate. ResultsFirst and second doses of SARS-CoV-2 vaccine markedly reduced risk of infection (first dose efficacy 68%, 95% CI 67% to 69%; second dose efficacy 88%, 95% CI 87 to 88%). In multivariable models, extended dosing intervals were associated with lowest risk of breakthrough infection (HR for redosing 0.64 (95% CI 0.61 to 0.67) at 6-8 weeks). Heterologous vaccine schedules that mixed viral vector vaccine first doses with mRNA second doses were significantly more effective than mRNA only vaccines. Risk of infection largely vanished during the time period 4-6 months after the second vaccine dose, but rose markedly thereafter. InterpretationA case-cohort design provided an efficient means to identify strong protective effects associated with SARS-CoV-2 vaccination, particularly after the second dose of vaccine. However, this effect appeared to wane once more than 6 months had elapsed since vaccination. Heterologous vaccination and extended dosing intervals improved the durability of immune response.

BackgroundThe current respiratory viral season in Ontario started early with an intensity experienced throughout the pediatric health system. We sought to examine trends in patient volumes and level of care intensity among children admitted with laboratory-confirmed respiratory viral infection over the last five years in Ottawa. MethodsThis was a retrospective cohort study of patients at CHEO, a pediatric health centre in Ottawa, who were diagnosed with a laboratory-confirmed respiratory viral infection in the first 72 hours of admission between October 22, 2017 and December 10, 2022. Their admissions were stratified by age groups and levels of care intensity and evaluated for trends over six surveillance periods that begin in Week 35 and end in Week 34 of the following calendar year. ResultsDuring this current surveillance period, there was an early, rapid, two-fold increase in admissions due to respiratory viral infections compared to previous periods, driven largely by RSV and influenza. While there were similar age distributions, there was a larger volume of Level 2 and 3 admissions, and higher proportion of patients requiring Level 2 intensity of care (20.8% versus 2.2% to 12.0% in pre-pandemic years; p<0.001). Lengths of stay were comparable to pre-pandemic surveillance years. InterpretationThe current viral season has been associated with elevated volumes and higher inpatient acuity compared to previous years and underscores the need for additional operational and human health resources to support pediatric health systems.

ObjectivesTo: 1) evaluate the effectiveness of COVID-19 vaccines among South Asians living in Ontario, Canada compared to non-South Asians, and 2) compare the odds of symptomatic COVID-19 infection and related hospitalizations and deaths among non-vaccinated South Asians and non-South Asians. DesignTest negative design study SettingOntario, Canada between Dec 14, 2020 and Nov 15, 2021 ParticipantsAll eligible individuals >18 years with symptoms of COVID-19 and subdivided by South Asian ethnicity versus other, and those who were vaccinated versus non-vaccinated. Main Outcome measuresThe primary outcome was vaccine effectiveness as defined by COVID-19 infections, hospitalizations, and deaths, and secondary outcome was the odds of COVID-19 infections, hospitalizations, and death comparing non-vaccinated South Asians to non-vaccinated non-South Asians. Results883,155 individuals were included. Among South Asians, two doses of COVID-19 vaccine prevented 93.8% (95% CI 93.2, 94.4) of COVID-19 infections and 97.5% (95% CI 95.2, 98.6) of hospitalizations and deaths. Among non-South Asians, vaccines prevented 86.6% (CI 86.3, 86.9) of COVID-19 infections and 93.1% (CI 92.2, 93.8) of hospitalizations and deaths. Non-vaccinated South Asians had higher odds of symptomatic SARS-CoV-2 infection compared to non-vaccinated non-South Asians (OR 2.35, 95% CI 2.3, 2.4), regardless of their immigration status. ConclusionsCOVID-19 vaccines are effective in preventing infections, hospitalizations and deaths among South Asians living in Canada. The observation that non-vaccinated South Asians have higher odds of symptomatic COVID-19 infection warrants further investigation. What is already known?Some ethnic communities, such as South Asians, were disproportionately impacted during the COVID-19 pandemic. However, there are limited data on COVID-19 vaccine efficacy among this high-risk ethnic group. What this study adds?- In this large population-based study including close to 900,000 individuals in Canada, we show COVID-19 vaccines are effective in preventing symptomatic SARS CoV-2 infections, hospitalizations and deaths among both South Asians and non-South Asians. - We also demonstrate that, among non-vaccinated individuals, South Asians have higher odds of COVID-19 infection, and an increased risk of COVID-19 hospitalizations and deaths compared to non-South Asians.

BackgroundUse of masks and respirators for prevention of respiratory infectious disease transmission is not new, but has proven controversial, and even politically polarizing during the SARS-CoV-2 pandemic. In the Canadian province of Ontario, mask mandates were introduced by the 34 regional health authorities in an irregular fashion from June to September 2020, creating a quasi-experiment that can be used to evaluate impact of community mask mandates. Ontario SARS-CoV-2 case counts were strongly biased by testing focussed on long-term care facilities and healthcare workers. We developed a simple regression-based test-adjustment method that allowed us to adjust cases for undertesting by age and gender. We used this test- adjusted time series to evaluate mask mandate effectiveness. MethodsWe evaluated the effect of masking using count-based regression models that allowed adjustment for age, sex, public health region and time trends with either reported (unadjusted) cases, or testing-adjusted case counts, as dependent variables. Mask mandates were assumed to take effect in the week after their introduction. Model based estimates of effectiveness were used to estimate the fraction of SARS- CoV-2 cases, severe outcomes, and costs, averted by mask mandates. ResultsModels that used unadjusted cases as dependent variable identified protective effects of masking (effectiveness 15-42%), though effectiveness was variably statistically significant, depending on model choice. Mask effectiveness in models predicting test-adjusted case counts was substantially higher, ranging from 49% (44- 53%) to 73% (48-86%) depending on model choice. Effectiveness was greater in women than men (P = 0.016), and in urban health units as compared to rural units (P < 0.001). The prevented fraction associated with mask mandates was 46% (41-51%), averting approximately 290,000 clinical cases, averting 3008 deaths and loss of 29,038 QALY. Costs averted represented $CDN 610 million in economic wealth. ConclusionsLack of adjustment for SARS-CoV-2 undertesting in younger individuals and males generated biased estimates of infection risk and obscures the impact of public health preventive measures. After adjustment for under-testing, the effectiveness of mask mandates emerges as substantial, and robust regardless of model choice. Mask mandates saved substantial numbers of lives, and prevented economic costs, during the SARS-CoV-2 pandemic in Ontario, Canada.

BackgroundThe COVID-19 pandemic placed immense strain on Canadas healthcare system and disproportionately affected individuals with poorer baseline health. Healthcare-associated infections (HAIs) increase risk for both patients and healthcare workers and are often more severe due to advanced age and comorbidities. While efforts have aimed to reduce in-hospital transmission, the individual- and community-level consequences of HAIs require further study. We aimed to assess whether healthcare-associated COVID-19 cases had higher odds of death compared to hospitalized community-acquired cases, and to evaluate the directionality of transmission between hospitals and the community. MethodsWe analyzed COVID-19 surveillance data from Ontarios Case Contact and Management System and the COVaxON vaccine registry (March 17, 2020, to September 4, 2022). Latent class analysis was used to classify hospitalized cases by likelihood of healthcare-associated infection. Mortality odds by category were estimated using binomial logistic regression. Directionality between hospital outbreaks and community cases was assessed using a modified Granger causality approach. FindingsCompared to patients with low likelihood of healthcare-associated infection, those moderately likely to have acquired COVID-19 in hospital had elevated odds of death (OR: 1.26, 95% CI: 1.14-1.40); no significant increase was seen in the high-likelihood group (OR: 1.05, 95% CI: 0.96-1.15). Community cases did not predict hospital outbreaks (p=0.5749), but hospital outbreaks predicted community case growth (p<0.0001). InterpretationHospital-acquired COVID-19 is associated with excess mortality and may drive community transmission. Preventing in-hospital transmission is critical to protecting patients and controlling broader epidemic spread. FundingSupported by a Canadian Institutes for Health Research project grant, #518192.