Ontario Research Articles

Nd isotope mapping in the Go Home region of Georgian Bay: a misunderstood key to the geology of the Central Gneiss Belt, Grenville Province of Ontario

The Georgian Bay transect forms an important geological section across the deeply exhumed Central Gneiss Belt of the Ontario Grenville Province. Its geological mapping was one of Nick Culshaw’s major research contributions, but the tectonic structure of the southern part of this transect in the Go Home region was never properly established. New Nd isotope data show that the classically recognized Go Home domain should be divided into three structural “decks” with distinct TDM (depleted mantle) Nd model ages. The upper deck consists of the Pine Island and Honey Harbour domains, with TDM ages averaging 1.56 and 1.57 Ga, respectively, which form two isolated units of the Grenvillian allochthonous belt. These are underlain by the newly-recognized Six Mile Lake domain, whose average TDM age of 1.71 Ga is representative of the tectonic duplex entrained elsewhere onto the base of the allochthon. Finally, the lowermost deck yields an average TDM age of 1.87 Ga, which identifies it as part of the Grenvillian parautochthon, exposed here in a tectonic window. The presence of a large retrogressed eclogite body within the allochthonous Honey Harbour domain confirms the exhumation of this unit from the deep crust on a major structural ramp. The coherent boundaries of these domains are consistent with the ramp–flat thrusting model of the Ottawan (Grenvillian) orogeny and limit the action of later extensional tectonics in the southwest Grenville Province.

Insights into Boreal Forest Disturbance from Canopy Stability Index

The world’s forests are being increasingly disturbed from exposure to the compounding impacts of land use and climate change, in addition to natural disturbance regimes. Boreal forests have a lower level of deforestation compared to tropical forests, and while they have higher levels of natural disturbances, the accumulated impact of forest management for commodity production coupled with worsening fire weather conditions and other climate-related stressors is resulting in ecosystem degradation and loss of biodiversity. We used satellite-based time-series analysis of two canopy indices—canopy photosynthesis and canopy water stress—to calculate an index that maps the relative stability of forest canopies in the Canadian provinces of Ontario and Quebec. By drawing upon available spatial time-series data on logging, wildfire, and insect infestation impacts, we were able to attribute the causal determinants of areas identified as having unstable forest canopy. The slope of the two indices that comprise the stability index also provided information as to where the forest is recovering from prior disturbances. The stability analyses and associated spatial datasets are available in an interactive web-based mapping app. that can be used to map disturbed forest canopies and the attribution of disturbances to human or natural causes. This information can assist decision-makers in identifying areas that are potentially ecologically degraded and in need of restoration and those stable areas that are a priority for protection.

A new patient navigation model of care to support older adults in transitions of care: Key considerations for implementation for policy-makers and health system leaders.

A Patient Navigation (PN) model of care was introduced in a large metropolitan hospital in Ontario (Canada) to support transitions in care for older adults in 2019. The patient navigator is a community social worker or "community transitional lead" embedded in the hospital's in care teams to assist with discharge planning and provide follow-up care to older adults, their families, and/or care partners for up to 90 days. Initially, the PN program supported acute care patients and has since expanded in the Emergency Department and Reactivation Care Centre. In this cohort retrospective observational study, we described the new PN model of care by analyzing the clinical notes collected by the patient navigator. This article provides preliminary insights for health leaders who are interested in implementing this novel PN model to improve transitions of care in a hospital setting. Funding was provided by the SLAIGHT Family Foundation.

Effects of aerial liming on soil chemical and biological properties in metal contaminated and inaccessible lands in Ontario (Canada).

The manual addition of lime to soil, in addition to tree planting and fertilization have been the dominant strategy described in restoration protocols for ecosystems damaged by acid rain and metal contamination. Investigations on aerial-limed soils in inaccessible lands are limited. The objective of this study was to assess the effects of aerial liming on soil pH, organic matter, microbial biomass, and enzymatic activities, and aboveground plant population quality in metal-contaminated lands in northern Ontario, Canada. Soil samples were collected from three sites around the City of Greater Sudbury with each pair being composed of a reclaimed (areal-limed) site and an adjacent undisturbed (unlimed) area. Soil physico-chemistry, microbial biomass (assessed by Phospholipid fatty acid analysis) and enzymatic activities were analyzed. Soil pH was higher in limed sites compared to unlimed at recently restored sites (Baby Lake and Wahnapitae) but not at the oldest reclaimed site (HWY 80 N). Organic matter was higher in limed areas compared to the unlimed reference site only at most recently reclaimed site at Baby Lake. Aboveground plant population health was visibly improved in limed sites compared to unlimed areas. Metal concentrations of iron (Fe) and arsenic (As), total microbial biomasses, gram-negative bacterial, fungal, and eukaryotic biomasses were all significantly increased in the limed soils compared to the unlimed samples. The same trend was observed for the activities of three of the enzymes tested, β-N-acetylglucosaminidase (BG), aryl sulfatase (AS), and glycine aminopeptidase (GAP). Interestingly, strong positive correlations between the levels of soil organic matter, microbial biomasses, and NAGase and ALP activities were observed. Although expensive, aerial liming is effective in restoring inaccessible sites impacted by smelting operations where other methods cannot easily be used.

COVID-19 in Perspective: A Witness Seminar1.

In June 2023, we brought together leaders who responded to the emergency phase COVID-19 pandemic in Ontario as part of a "Witness Seminar." This approach to studying history was developed by the Institute of Contemporary British History. It has been extensively used in the history of science and medicine by the Wellcome Trust History of Twentieth Century Medicine. A witness seminar provides a collective oral history, in which participants can express diverse perspectives, build on each other's thoughts, and create a documentary record for policy makers and future historians. The published transcript provides an intimate look at how the pandemic played out in the eyes of some of key responders and raises many questions about the history of public health funding and administration in the province of Ontario, the failures in long-term care, and the need to improve pandemic communication. This article documents the success of the pandemic response.

A multi-dimensional evaluation of upgrading fenestration systems in single-family dwellings and implications for rebate structures

This paper presents a novel methodology of four interdependent stages to evaluate the economic, environmental, and health benefits of replacing low-energy performing residential windows with higher-performing ones in single-family dwellings. A modeling-based approach is developed to compute and monetize reduction in heating and cooling energy transmittance, greenhouse gas emissions, and premature mortality associated with the decrease in the outdoor fine particulate matter. Linear regression models of energy prices, carbon pricing, and a value per statistical life approach quantify these benefits monetarily. Factors like upgrade type, dwelling window-to-wall ratio, deterioration in energy performance, geographic location, and window placement by orientation are analyzed for their impact on benefits. A case study examining two locations in the province of Ontario, Canada, is carried out. Results show that energy bill saving is sufficient to justify investing in windows with energy-efficient recognition across all dwelling categories in Southern Ontario, though government rebates are necessary for some dwelling types opting to upgrade to the most energy-efficient models. In contrast, rebates are unnecessary in Northern Ontario for any upgraded models due to substantial energy bill savings. The study proposes a per-window rebate policy based on realized benefits, considering various upgrade models, distinct single-detached dwellings, and geographic location eligibility.

Using newly linked hospital and population data to identify opportunities to reduce harms from sedative-hypnotic prescribing at population scale

Objective and ApproachSedative-hypnotic medications are associated with harms such as delirium and falls, and may be overprescribed in hospitals. Measuring potentially inappropriate in-hospital sedative-hypnotic prescriptions requires distinguishing new initiations from pre-hospital prescriptions, but pre-hospital medications may not be captured in hospital data. To quantify physician- and hospital-level variation in sedative-hypnotic prescribing, we use linked data between GEMINI (which includes EMR data from >1.8 million admissions across 30 hospitals, approximately 60% of medical inpatient beds in Ontario) and ICES (which houses administrative healthcare databases, including outpatient prescriptions for adults ≥65 years). We will validate whether data in hospital clinical notes or pharmacy records can reliably identify pre-hospital prescriptions. ResultsUsing provincial health insurance number, 98.1% of GEMINI records could successfully be linked deterministically to ICES. Our exploratory sedative-hypnotic cohort included 90,806 general medicine patients treated by 437 physicians from 17 hospitals across Ontario from 2021-2022. Median age was 72 years and 48.7% were female. The proportion of patients receiving a new sedative-hypnotic prescription varied markedly across hospitals (median 0.21, range 0.04-0.41) and across physicians within hospitals (median within-hospital difference between lowest and highest prescriber: 0.18, range of within-hospital differences 0.07-0.67). Validation of new rather than continued prescriptions is underway. Full results will be ready for presentation at the conference. ConclusionSedative-hypnotic prescribing is common and highly variable in hospitals across Ontario, indicating an opportunity to improve patient safety. Implications Based on these analyses, the province of Ontario has made reducing in-hospital sedative-hypnotic prescribing a provincial priority for 2023-2024.

Green Belt Legislation Regulation: Comparative Legal Research

Recently, legislative acts on the protection of the green belt have been increasingly adopted in various states. Using the legislation examples of the United Kingdom, the Canadian province of Ontario, and Russia, we have identified public relations that can be the subject of regulation of such legislation. Based on the analysis of typical legal conflicts, the problem areas which need the most attention of the legislator have been identified. The methods of differentiation of the legal regime for various areas within the green belt are investigated, taking into account their geographical features and specific management goals. The most promising areas for legal regulation that require the increased attention of legislators speak to the establishment of the procedures and criteria for excluding land plots from the green belt, the regulation of village development processes within the green belt, the establishment of a comprehensive list of agricultural types of permitted use, and the establishment of the procedure for the development of specialized plans or strategies for the use and protection of the green belt. The article offers solutions to these issues. The methodology of comparative law, including the functional method, was used in the study.

An Exploration of Sexual Consent Beliefs, Attitudes, and Behaviors among Middle School Students in Canada

An essential component of healthy sexual exploration is the understanding of sexual consent. Unfortunately, sexual consent is not consistently taught in sex education programs developed for adolescents. Furthermore, although early adolescence is a critical developmental period for the formation of sexual identity, norms, attitudes, and relationships, this population is underrepresented in the sexual consent literature. To fill this important gap, this study examined the sexual consent beliefs, attitudes, and behaviors of 254 middle school students from a large, urban city in the province of Ontario. Correlates and predictors of sexual consent endorsement were tested via bivariate and multiple regression analyses. Greater perceived negative sanctions of dating violence and higher endorsement of gender stereotypes emerged as variables significantly related to and predictive of sexual consent attitudes, perceived behavioral control, and affirmative consent norms. Gender was also a significant correlate, as girls were more likely than boys to endorse affirmative sexual consent beliefs, attitudes, and behaviors. The findings highlight important group differences and provide guidance for the design and implementation of sexual education and prevention programs.

Hysterectomy Rate Following Endometrial Ablation in Ontario: A Cohort Analysis of 76,446 Patients

Background: Endometrial Ablation (EA) is an alternative to hysterectomy for the management of abnormal uterine bleeding (AUB); however, it does not eliminate the need for future surgical re-intervention. Objectives: The primary objective of this study was to establish long-term clinical outcomes including the risk of hysterectomy in women who had undergone a primary EA. Materials and Methods: This is a retrospective population-based cohort study utilising administrative data from the Canadian province of Ontario. This study assesses patients undergoing surgery in a publicly funded health care system. Main Outcome Measures: We assessed women in Ontario undergoing a primary EA over a 15-year period. The primary outcome was hysterectomy within 5 years of primary EA. Secondary outcomes included myomectomy and repeat EA. All outcomes were also reported for 1, 3, 5, 10 and 15 years of follow-up. Logistic regression was used to establish predictors of hysterectomy within 5 years of primary EA. Results: A total of 76,446 primary EAs were evaluated from 2002-2017, with 16,480 (21.56%) undergoing a subsequent surgical intervention. The average age of primary EA was 43.8 (+/- 6.3) years. Within 5 years, the evaluable cohort was 52,464, with 8,635 (16.46%) of women having proceeded to hysterectomy, 664 (1.27%) to myomectomy, and 2,468 (2.8%) to repeat ablation. By 15-years follow-up, the evaluable cohort was 1,788, with 28.75% had undergone a hysterectomy, 2.01% a myomectomy, and 5.20% a repeat EA. On logistic regression analysis, advancing age at time of EA was associated with significantly decreased odds of hysterectomy (OR=0.94, 95% CI 0.935-0.944, p<.0001) as was increasing surgical experience (OR=0.997, 95% CI 0.994-1.000, p=.022). Conversely, complex diagnosis (OR=1.102, 95% CI 1.042-1.164, p<.0001) and previous abdominal surgery (OR=1.288, 95% CI 1.222-1.357, p<0.0001) were associated with increased risk of subsequent hysterectomy. Conclusion: Primary EA is associated with a high risk of progression to subsequent hysterectomy or other surgical intervention, without evidence of plateau of risk with long term follow-up. What is new? This study has the longest follow-up assessing hysterectomy outcomes in women undergoing a primary EA, with 28.75% of women having undergone a hysterectomy within 15 years of their EA.

Hysterectomy Rate Following Endometrial Ablation in Ontario: A Cohort Analysis of 76,446 Patients

Background: Endometrial Ablation (EA) is an alternative to hysterectomy for the management of abnormal uterine bleeding (AUB); however, it does not eliminate the need for future surgical re-intervention. Objectives: The primary objective of this study was to establish long-term clinical outcomes including the risk of hysterectomy in women who had undergone a primary EA. Materials and Methods: This is a retrospective population-based cohort study utilising administrative data from the Canadian province of Ontario. This study assesses patients undergoing surgery in a publicly funded health care system. Main Outcome Measures: We assessed women in Ontario undergoing a primary EA over a 15-year period. The primary outcome was hysterectomy within 5 years of primary EA. Secondary outcomes included myomectomy and repeat EA. All outcomes were also reported for 1, 3, 5, 10 and 15 years of follow-up. Logistic regression was used to establish predictors of hysterectomy within 5 years of primary EA. Results: A total of 76,446 primary EAs were evaluated from 2002-2017, with 16,480 (21.56%) undergoing a subsequent surgical intervention. The average age of primary EA was 43.8 (+/- 6.3) years. Within 5 years, the evaluable cohort was 52,464, with 8,635 (16.46%) of women having proceeded to hysterectomy, 664 (1.27%) to myomectomy, and 2,468 (2.8%) to repeat ablation. By 15-years follow-up, the evaluable cohort was 1,788, with 28.75% had undergone a hysterectomy, 2.01% a myomectomy, and 5.20% a repeat EA. On logistic regression analysis, advancing age at time of EA was associated with significantly decreased odds of hysterectomy (OR=0.94, 95% CI 0.935-0.944, p<.0001) as was increasing surgical experience (OR=0.997, 95% CI 0.994-1.000, p=.022). Conversely, complex diagnosis (OR=1.102, 95% CI 1.042-1.164, p<.0001) and previous abdominal surgery (OR=1.288, 95% CI 1.222-1.357, p<0.0001) were associated with increased risk of subsequent hysterectomy. Conclusion: Primary EA is associated with a high risk of progression to subsequent hysterectomy or other surgical intervention, without evidence of plateau of risk with long term follow-up. What is new? This study has the longest follow-up assessing hysterectomy outcomes in women undergoing a primary EA, with 28.75% of women having undergone a hysterectomy within 15 years of their EA.

Platform-mediated territorial stigmatization and destigmatization: Unpacking Reddit discussions on moving to “the other” London

This paper interrogates the role of digital platforms in advancing territorial stigma. Drawing from research that has discerned the channels with which territorial stigma has been produced and mediated through — commonly referred to as ‘modes’ — I argue digital platforms are a mode in their own right. Digital platforms are on par with, and may have already surpassed, pre-platform media modes (e.g., newspapers, television) in terms of their use for forming preconceptions of cities in lieu of lived experience. Accordingly, this study investigates discussions on the social networking platform Reddit, about moving to the mid-sized city of London, Ontario in Canada. I use a hybrid thematic analysis to identify (de)stigmatizing content within a topic-based forum (a subreddit). The results show that the platform mediated its users’ reproduction of territorial stigmas stemming from pre-platform modes, rather than having generated entirely novel stigmas. Moreover, many users enacted or reworked established territorial destigmatization strategies to contest, counter, or cope with London’s territorial stigma. This paper contributes to territorial stigma research by examining a lesser-known mid-sized city, which in turn expands the current understanding of stigmatization in Canada hitherto limited to its materialization in large cities. By demonstrating Reddit’s modal potentiality, the paper provides the necessary empirical basis for future studies interested in examining other digital platforms through the theoretical framework of territorial stigma. Furthermore, it encourages future conceptualizations of the media mode of territorial stigma production to include digital platforms alongside traditional and mass media.

Longer-term impacts of the COVID-19 pandemic on obstructive sleep apnoea (OSA)-related healthcare: a province-based study

RationaleFollowing marked reductions in sleep medicine care early in the COVID-19 pandemic, there is limited information about the recovery of these services. We explored long-term trends in obstructive sleep apnoea...

Length of Postpartum Hospital Stays During COVID-19: Findings From a Convergent Parallel Mixed-Methods Study

ObjectivesWe examined the length of postpartum hospitalization for live births during the COVID-19 pandemic and explored how pandemic circumstances influenced postpartum hospital experiences. MethodsWe conducted a cross-provincial, convergent parallel mixed-methods study in Ontario (ON) and British Columbia (BC), Canada. We included birthing persons (BPs) with an in-hospital birth in ON from 1 January to 31 March 2019, 2021, and 2022 (quantitative), and BPs (≥18 years) in ON or BC from 1 May 2020 to 1 December 2021 (qualitative). We linked multiple health administrative datasets at ICES and developed multivariable linear regression models to examine the length of hospital stay (quantitative). We conducted semi-structured interviews using qualitative descriptive to understand experiences of postpartum hospitalization (qualitative). Data integration occurred during design and interpretation. ResultsRelative to 2019, postpartum hospital stays decreased significantly by 3.29 hours (95% CI –3.58 to –2.99; 9.2% reduction) in 2021 and 3.89 hours (95% CI –4.17 to –3.60; 9.0% reduction) in 2022. After adjustment, factors associated with shortened stays included: giving birth during COVID-19, social deprivation (more ethnocultural diversity), midwifery care, multiparity, and lower newborn birth weight. Postpartum hospital experiences were impacted by risk perception of COVID-19 infection, clinical care and hospital services/amenities, visitor policies, and duration of stay. ConclusionsLength of postpartum hospital stays decreased during COVID-19, and qualitative findings described unmet needs for postpartum services. The integration of large administrative and interview data expanded our understanding of observed differences. Future research should investigate the impacts of shortened stays on health service outcomes and personal experiences.

Comparing birth experiences and satisfaction with midwifery care before and after the implementation of Canada's first Alongside Midwifery Unit (AMU).

Globally, midwifery-led birthing units are associated with favourable clinical outcomes and positive birth experiences. As part of our evaluation of Canada's first Alongside Midwifery Unit (AMU) at Markham Stouffville Hospital, we sought to explore and compare birth experiences and satisfaction among midwifery clients who gave birth on the AMU with midwifery clients who gave birth on the traditional obstetric unit prior to AMU implementation. We conducted a structured, online, cross-sectional survey of midwifery clients in the six months before, and up to 18 months after, opening of the AMU at Markham Stouffville Hospital, Ontario Canada. The survey contained validated measures of satisfaction including personal capacity and participation; perceived safety, control, and security; professional support; and satisfaction. Descriptive statistics and tests of significance were completed in SPSS. A total of 193 responses were included in our analyses (pre-AMU n = 47, post-AMU n = 146). All participants had positive experiences in the four domains assessed. Compared to those who gave birth with midwives on the Labour unit, those who gave birth on the AMU indicated more positive experiences for some measures. Perceptions pertaining to being an active participant in care, to security and sense of control were more positive among those who gave birth on the AMU. The AMU in Ontario is associated with high levels of satisfaction during birth, particularly the perception of being actively engaged in decision making, having a sense of control and safety, and having confidence in the care provider team. Care received on the AMU does not compromise birth experiences or satisfaction and may be associated with greater autonomy and agency for the person giving birth.

Comparative Safety Analysis of Nabilone Versus Opioids: A Population-Based Cohort Study.

Some have advocated that nabilone be used rather than opioids to manage chronic, noncancer pain, since the former drug may have a better safety profile. We compared the safety of incident nabilone use relative to incident opioid use with respect to multiple clinically important outcomes. A population-based, retrospective cohort study. Province of Ontario, Canada. Persons aged 12 years and older, diagnosed with a musculoskeletal condition within the past 3 years prior to the index date. Incident nabilone use, with incident opioid use serving as the reference group. Within 3 months following the index date, we separately evaluated for pneumonia, motor vehicle accidents, falls or fractures, mental and behavioral disorder due to psychoactive substance use, and all-cause mortality. A total of 18,863 incident nabilone users were propensity score matched to an equal number of opioid users. In the overall matched analysis, incident nabilone users vs. incident opioid users had significantly lower rates of pneumonia (hazard ratio [HR] 0.78, 95% CI 0.63-0.96), falls or fractures (HR 0.56, 95% CI 0.50-0.64), and all-cause mortality (HR 0.79, 95% CI 0.65-0.95), but significantly higher rate of mental or behavioral disorder (HR 2.23, 95% CI 1.45-3.43). There was no significant difference between groups with respect to rate of motor vehicle accidents. Unmeasured confounding may have influenced results. While usage of nabilone relative to opioids was associated with reduced rates of pneumonia, falls or fractures, and all-cause mortality, it was simultaneously associated with an increased rate of adverse mental health outcomes. This picture of mixed safety results raises concerns with the policy approach of broadly substituting use of opioids with nabilone. Ontario Ministry of Health.

The associations of supervised consumption services with the rates of opioid-related mortality and morbidity outcomes at the public health unit level in Ontario (Canada): A controlled interrupted time-series analysis.

This study aimed to assess the impact of the implementation of legally sanctioned supervised consumption sites (SCS) in the Canadian province of Ontario on opioid-related deaths, emergency department (ED) visits and hospitalisations at the public health unit (PHU) level. Monthly rates per 100,000 population of opioid-related deaths, ED visits and hospitalisations for PHUs in Ontario between December 2013 and March 2022 were collected. Aggregated and individual analyses of PHUs with one or more SCS were conducted, with PHUs that instituted an SCS being matched to control units that did not. Autoregressive integrated moving average models were used to estimate the impact of SCS implementation on opioid-related deaths, ED visits and hospitalisations. Twenty-one legally sanctioned SCS were implemented across nine PHUs in Ontario during the study period. Interrupted time series analyses showed no statistically significant changes in opioid-related death rates in aggregated analyses of intervention PHUs (increase of 0.02 deaths/100,000 population/month; p = 0.27). Control PHUs saw a significant increase of 0.38 deaths/100,000 population/month; p < 0.001. No statistically significant changes were observed in the rates of opioid-related ED visits in intervention PHUs (decrease of 0.61 visits/100,000 population/month; p = 0.39) or controls (increase of 0.403 visits; p = 0.76). No statistically significant changes to the rates of opioid-related hospitalisations were observed in intervention PHUs (0 hospitalisations/100,000 population/month; p = 0.98) or controls (decrease of 0.05 hospitalisations; p = 0.95). This study did not find significant mortality or morbidity effects associated with SCS availability at the population level in Ontario. In the context of a highly toxic drug supply, additional interventions will be required to reduce opioid-related harms.

The Coronavirus Pandemic and Mental Health Presentations of Young Children.

Children under the age of four are emotionally vulnerable to global disasters, such as the COVID-19 pandemic given the lack of socialization opportunities and coping mechanisms, and susceptibility to heightened caregiver stress. Currently, the extent to which the pandemic impacted the mental health of clinically referred young children is unknown. To evaluate how children's mental health outcomes were impacted during the pandemic, interRAI Early Years assessments (N = 1343) were obtained from 11 agencies across the Province of Ontario, during pre-pandemic and pandemic timepoints. Findings demonstrated that the number of completed assessments declined during the pandemic. Further, children's emotional concerns differed before and during the pandemic, whereby children exhibited greater emotional dysregulation during the pandemic. However, there were no significant differences when examining caregiver distress, parenting strengths, child distractibility/inattention or behavioural issues. Implications for young children and their families, clinicians, and policy makers are discussed.

Biologically Effective Dose of Diflufenican for the Control of Multiple Herbicide-Resistant Waterhemp in Soybean

Waterhemp biotypes have evolved resistance to Weed Science Society of America (WSSA) Herbicide Groups 2, 5, 9, 14, and 27 in Ontario Canada, are present in 15 counties, spanning a distance of 800 km across southern Ontario, and cause an average soybean yield loss of 42%. Five field experiments were established in growers&amp;rsquo; fields in southwestern Ontario to determine the biologically effective doses of diflufenican (Group 12) applied preemergence (PRE) to control multiple herbicide-resistant waterhemp in soybean. The calculated diflufenican doses to elicit 50, 80, and 95% control of MHR waterhemp were 71, 164, and 304 g ai ha-1 at 2 weeks after herbicide application (WAA); 50, 115, and 214 g ai ha-1 at 4 WAA; and 69, 158, and 294 g ai ha-1 at 8 WAA, respectively. The calculated diflufenican doses that caused a 50, 80, and 95% reduction in MHR waterhemp density were 28, 70, and Non-est. g ai ha-1 and the doses that caused a 50, 80, and 95% reduction in MHR waterhemp biomass were 44, 109, and Non-est. g ai ha-1, respectively. The calculated diflufenican doses that resulted in 50, 80, and 95% of the soybean yield of the industry standard herbicide (flumioxazin/pyroxasulfone) were 3, 12, and 57 g ai ha-1, respectively. Diflufenican (180 g ai ha-1) PRE controlled MHR waterhemp 89, 92, and 85%; metribuzin (300 g ai ha-1) PRE controlled MHR waterhemp 94, 84, and 69%; and flumioxazin/pyroxasulfone (105/134 g ai ha-1) PRE controlled MHR waterhemp 100, 99, and 98% at 2, 4, and 8 WAA, respectively. Diflufenican, metribuzin, and flumioxazin/pyroxasulfone applied PRE reduced MHR waterhemp density 96, 84, and 100% and biomass 93, 67, and 99%, respectively at 8 WAA. Diflufenican, metribuzin, and flumioxazin/pyroxasulfone applied PRE caused 9, 0, and 4% visible soybean injury, respectively but the injury was transient and caused no adverse effect on seed moisture content or seed yield of soybean. This study concludes that diflufenican and metribuzin applied PRE provide comparable MHR waterhemp control; however, control was lower than flumioxazin/pyroxasulfone.

Case-cohort design as an efficient approach to evaluating COVID-19 vaccine effectiveness, waning, heterologous immune effect and optimal dosing interval

Though widely applied in other epidemiological fields, the case-cohort study design has seen little application in the field of vaccinology. Case-cohort studies use probabilistic sampling and reweighting to draw inferences about effects (in this case vaccine efficacy) at the population level in an efficient manner. The SARS-CoV-2 pandemic was met with high vaccine uptake, and high rates of population testing prior to the emergence of Omicron variants of concern, in Ontario, Canada, providing an ideal environment for application of case-cohort methodology. We combined a population-based case line list and vaccination database for the province of Ontario 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. First and second doses of SARS-CoV-2 vaccine markedly reduced risk of infection (first dose efficacy 68 %, 95 % CI 67 %–69 %; second dose efficacy 88 %, 95 % CI 87–88 %). In multivariable models, extended dosing intervals were associated with lowest risk of breakthrough infection (HR for redosing 0.64 (95 % CI 0.61–0.67) 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. We conclude that a case-cohort design provided an efficient means to identify strong protective effects associated with SARS-CoV-2 vaccination in real time, and also served to quantify the timing and magnitude of infection breakthrough risk in the same cohort. Heterologous vaccination and extended dosing intervals improved the durability of immune response.