Risk of hospital admission and death from first-ever SARS-CoV-2 infection by age group during the Delta and Omicron periods in British Columbia, Canada.

BACKGROUND: Population-based cross-sectional serosurveys within the Lower Mainland, British Columbia, Canada, showed about 10%, 40% and 60% of residents were infected with SARS-CoV-2 by the sixth (September 2021), seventh (March 2022) and eighth (July 2022) serosurveys. We conducted the ninth (December 2022) and tenth (July 2023) serosurveys and sought to assess risk of severe outcomes from a first-ever SARS-CoV-2 infection during intersurvey periods. METHODS: Using increments in cumulative infection-induced seroprevalence, population census, discharge abstract and vital statistics data sets, we estimated infection hospitalization and fatality ratios (IHRs and IFRs) by age and sex for the sixth to seventh (Delta/Omicron-BA.1), seventh to eighth (Omicron-BA.2/BA.5) and eighth to ninth (Omicron-BA.5/BQ.1) intersurvey periods. As derived, IHR and IFR estimates represent the risk of severe outcome from a first-ever SARS-CoV-2 infection acquired during the specified intersurvey period. RESULTS: The cumulative infection-induced seroprevalence was 74% by December 2022 and 79% by July 2023, exceeding 80% among adults younger than 50 years but remaining less than 60% among those aged 80 years and older. Period-specific IHR and IFR estimates were consistently less than 0.3% and 0.1% overall. By age group, IHR and IFR estimates were less than 1.0% and up to 0.1%, respectively, except among adults aged 70-79 years during the sixth to seventh intersurvey period (IHR 3.3% and IFR 1.0%) and among those aged 80 years and older during all periods (IHR 4.7%, 2.2% and 3.5%; IFR 3.3%, 0.6% and 1.3% during the sixth to seventh, seventh to eighth and eighth to ninth periods, respectively). The risk of severe outcome followed a J-shaped age pattern. During the eighth to ninth period, we estimated about 1 hospital admission for COVID-19 per 300 newly infected children younger than 5 years versus about 1 per 30 newly infected adults aged 80 years and older, with no deaths from COVID-19 among children but about 1 death per 80 newly infected adults aged 80 years and older during that period. INTERPRETATION: By July 2023, we estimated about 80% of residents in the Lower Mainland, BC, had been infected with SARS-CoV-2 overall, with low risk of hospital admission or death; about 40% of the oldest adults, however, remained uninfected and at highest risk of a severe outcome. First infections among older adults may still contribute substantial burden from COVID-19, reinforcing the need to continue to prioritize this age group for vaccination and to consider them in health care system planning.

Comparative Single-Dose mRNA and ChAdOx1 Vaccine Effectiveness Against Severe Acute Respiratory Syndrome Coronavirus 2, Including Variants of Concern: Test-Negative Design, British Columbia, Canada.

BACKGROUND: In British Columbia, Canada, most adults 50-69 years old became eligible for severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) vaccine in April 2021, with chimpanzee adenoviral vectored vaccine (ChAdOx1) restricted to ≥55-year-olds and second doses deferred ≥6 weeks to optimize single-dose coverage. METHODS: Among adults 50-69 years old, single-dose messenger RNA (mRNA) and ChAdOx1 vaccine effectiveness (VE) against SARS-CoV-2 infection and hospitalization, including variant-specific, was assessed by test-negative design between 4 April and 2 October 2021. RESULTS: Single-dose VE included 11 861 cases and 99 544 controls. Median of postvaccination follow-up was 32 days (interquartile range, 15-52 days). Alpha, Gamma, and Delta variants comprised 23%, 18%, and 56%, respectively, of genetically characterized viruses. At 21-55 days postvaccination, single-dose mRNA and ChAdOx1 VE (95% confidence interval [CI]) was 74% (71%-76%) and 59% (53%-65%) against any infection and 86% (80%-90%) and 94% (85%-97%) against hospitalization, respectively. VE (95% CI) was similar against Alpha and Gamma infections for mRNA (80% [76%-84%] and 80% [75%-84%], respectively) and ChAdOx1 (69% [60%-76%] and 66% [56%-73%], respectively). mRNA VE was lower at 63% (95% CI, 56%-69%) against Delta but 85% (95% CI, 71%-92%) against Delta-associated hospitalization (nonestimable for ChAdOx1). CONCLUSIONS: A single mRNA or ChAdOx1 vaccine dose gave important protection against SARS-CoV-2, including early variants of concern. ChAdOx1 VE was lower against infection, but 1 dose of either vaccine reduced the hospitalization risk by >85% to at least 8 weeks postvaccination. Findings inform program options, including longer dosing intervals.

Single-dose mRNA Vaccine Effectiveness Against Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2), Including Alpha and Gamma Variants: A Test-negative Design in Adults 70 Years and Older in British Columbia, Canada.

BACKGROUND: Randomized-controlled trials of messenger RNA (mRNA) vaccine protection against severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) included relatively few elderly participants. We assess single-dose mRNA vaccine effectiveness (VE) in adults ≥ 70 years old in British Columbia, Canada, where second doses were deferred by up to 16 weeks and where a spring 2021 wave uniquely included codominant circulation of Alpha (B.1.1.7) and Gamma (P.1) variants of concern (VOC). METHODS: Analyses included community-dwelling adults ≥ 70 years old with specimen collection between 4 April (epidemiological week 14) and 1 May (week 17) 2021. Adjusted VE was estimated by test-negative design. Cases were reverse-transcription polymerase chain reaction (RT-PCR) test-positive for SARS-CoV-2, and controls were test-negative. Vaccine status was defined by receipt of a single-dose ≥ 21 days before specimen collection, but a range of intervals was assessed. Variant-specific VE was estimated against viruses genetically characterized as Alpha, Gamma or non-VOC lineages. RESULTS: VE analyses included 16 993 specimens: 1226 (7%) test-positive cases and 15 767 test-negative controls. Of 1131 (92%) genetically characterized viruses, 509 (45%), 314 (28%), and 276 (24%) were Alpha, Gamma, and non-VOC lineages, respectively. At 0-13 days postvaccination, VE was negligible at 14% (95% confidence interval [CI], 0-26) but increased from 43% (95% CI, 30-53) at 14-20 days to 75% (95% CI, 63-83) at 35-41 days postvaccination. VE at ≥ 21 days postvaccination was 65% (95% CI, 58-71) overall: 72% (95% CI, 58-81), 67% (95% CI, 57-75), and 61% (95% CI, 45-72) for non-VOC, Alpha, and Gamma variants, respectively. CONCLUSIONS: A single dose of mRNA vaccine reduced the risk of SARS-CoV-2 by about two-thirds in adults ≥ 70 years old, with protection only minimally reduced against Alpha and Gamma variants.

Two-Dose Severe Acute Respiratory Syndrome Coronavirus 2 Vaccine Effectiveness With Mixed Schedules and Extended Dosing Intervals: Test-Negative Design Studies From British Columbia and Quebec, Canada.

BACKGROUND: The Canadian coronavirus disease 2019 (COVID-19) immunization strategy deferred second doses and allowed mixed schedules. We compared 2-dose vaccine effectiveness (VE) by vaccine type (mRNA and/or ChAdOx1), interval between doses, and time since second dose in 2 of Canada's larger provinces. METHODS: Two-dose VE against severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection or hospitalization among adults ≥18 years, including due to Alpha, Gamma, and Delta variants of concern (VOCs), was assessed ≥14 days postvaccination by test-negative design studies separately conducted in British Columbia and Quebec, Canada, between 30 May and 27 November (epi-weeks 22-47) 2021. RESULTS: In both provinces, all homologous or heterologous mRNA and/or ChAdOx1 2-dose schedules were associated with ≥90% reduction in SARS-CoV-2 hospitalization risk for ≥7 months. With slight decline from a peak of >90%, VE against infection was ≥80% for ≥6 months following homologous mRNA vaccination, lower by ∼10% when both doses were ChAdOx1 but comparably high following heterologous ChAdOx1 + mRNA receipt. Findings were similar by age group, sex, and VOC. VE was significantly higher with longer 7-8-week versus manufacturer-specified 3-4-week intervals between mRNA doses. CONCLUSIONS: Two doses of any mRNA and/or ChAdOx1 combination gave substantial and sustained protection against SARS-CoV-2 hospitalization, spanning Delta-dominant circulation. ChAdOx1 VE against infection was improved by heterologous mRNA series completion. A 7-8-week interval between first and second doses improved mRNA VE and may be the optimal schedule outside periods of intense epidemic surge. Findings support interchangeability and extended intervals between SARS-CoV-2 vaccine doses, with potential global implications for low-coverage areas and, going forward, for children.

Serial cross-sectional estimation of vaccine-and infection-induced SARS-CoV-2 seroprevalence in British Columbia, Canada.

BACKGROUND: The evolving proportion of the population considered immunologically naive versus primed for more efficient immune memory response to SARS-CoV-2 has implications for risk assessment. We sought to chronicle vaccine- and infection-induced seroprevalence across the first 7 waves of the COVID-19 pandemic in British Columbia, Canada. METHODS: During 8 cross-sectional serosurveys conducted between March 2020 and August 2022, we obtained anonymized residual sera from children and adults who attended an outpatient laboratory network in the Lower Mainland (Greater Vancouver and Fraser Valley). We used at least 3 immunoassays per serosurvey to detect SARS-CoV-2 spike and nucleocapsid antibodies. We assessed any seroprevalence (vaccineor infection-induced, or both), defined by positivity on any 2 assays, and infection-induced seroprevalence, also defined by dual-assay positivity but requiring both antinucleocapsid and antispike detection. We used estimates of infection-induced seroprevalence to explore underascertainment of infections by surveillance case reports. RESULTS: By January 2021, we estimated that any seroprevalence remained less than 5%, increasing with vaccine rollout to 56% by May-June 2021, 83% by September-October 2021 and 95% by March 2022. Infection-induced seroprevalence remained less than 15% through September-October 2021, increasing across Omicron waves to 42% by March 2022 and 61% by July-August 2022. By August 2022, 70%-80% of children younger than 20 years and 60%-70% of adults aged 20-59 years had been infected, but fewer than half of adults aged 60 years and older had been infected. Compared with estimates of infection-induced seroprevalence, surveillance case reports underestimated infections 12-fold between September 2021 and March 2022 and 92-fold between March 2022 and August 2022. INTERPRETATION: By August 2022, most children and adults younger than 60 years had evidence of both SARS-CoV-2 vaccination and infection. As previous evidence suggests that a history of both exposures may induce stronger, more durable hybrid immunity than either exposure alone, older adults - who have the lowest infection rates but highest risk of severe outcomes - continue to warrant prioritized vaccination.

Priorities among effective clinical preventive services in British Columbia, Canada.

BACKGROUND: Despite the long-standing experience of rating the evidence for clinical preventive services, the delivery of effective clinical preventive services in Canada and elsewhere is less than optimal. We outline an approach used in British Columbia to assist in determining which effective clinical preventive services are worth doing. METHODS: We calculated the clinically preventable burden and cost-effectiveness for 28 clinical preventive services that received a 'strong or conditional (weak) recommendation for' by the Canadian Task Force on Preventive Health Care or an 'A' or 'B' rating by the United States Preventive Services Task Force. Clinically preventable burden is the total quality adjusted life years that could be gained if the clinical preventive services were delivered at recommended intervals to a British Columbia birth cohort of 40,000 individuals over the years of life that the service is recommended. Cost-effectiveness is the net cost per quality adjusted life year gained. RESULTS: Clinical preventive services with the highest population impact and best value for money include services that address tobacco use in adolescents and adults, exclusive breastfeeding, and screening for hypertension and other cardiovascular disease risk factors followed by appropriate pharmaceutical treatment. In addition, alcohol misuse screening and brief counseling, one-time screening for hepatitis C virus infection in British Columbia adults born between 1945 and 1965, and screening for type 2 diabetes approach these high-value clinical preventive services. CONCLUSIONS: These results enable policy makers to say with some confidence what preventive manoeuvres are worth doing but further work is required to determine the best way to deliver these services to all those eligible and to establish what supportive services are required. After all, if a clinical preventive service is worth doing, it is worth doing well.

Rapid Increase in SARS-CoV-2 P.1 Lineage Leading to Codominance with B.1.1.7 Lineage, British Columbia, Canada, January-April 2021.

Several severe acute respiratory syndrome coronavirus 2 variants of concern (VOCs) emerged in late 2020; lineage B.1.1.7 initially dominated globally. However, lineages B.1.351 and P.1 represent potentially greater risk for transmission and immune escape. In British Columbia, Canada, B.1.1.7 and B.1.351 were first identified in December 2020 and P.1 in February 2021. We combined quantitative PCR and whole-genome sequencing to assess relative contribution of VOCs in nearly 67,000 infections during the first 16 weeks of 2021 in British Columbia. B.1.1.7 accounted for <10% of screened or sequenced specimens early on, increasing to >50% by week 8. P.1 accounted for <10% until week 10, increased rapidly to peak at week 12, and by week 13 codominated within 10% of rates of B.1.1.7. B.1.351 was a minority throughout. This rapid expansion of P.1 but suppression of B.1.351 expands our understanding of population-level VOC patterns and might provide clues to fitness determinants for emerging VOCs.

The Impact of Treatment as Prevention on the HIV Epidemic in British Columbia, Canada.

PURPOSE OF REVIEW: This study proposes to describe the impact of a publicly funded Treatment as Prevention (TasP) strategy in British Columbia (BC), Canada, in decreasing the individual and public health impact of the HIV/AIDS Epidemic. RECENT FINDINGS: In BC, TasP has been associated with a steady decline in HIV-related morbidity and mortality. At the same time, a demographic transition was observed among people living with HIV (PLWH), with the majority of those on antiretroviral treatment (ART) now ≥ 50 years of age, living with at least one comorbidity, and dying from age-associated comorbidities. We also documented a progressive increase in the proportion of viral load suppression as a result of ART expansion. While the pre-ART CD4 T cell count has increased steadily in recent years, there is still a large proportion of PLWH being diagnosed in later stages of HIV infection. New HIV diagnoses have been rapidly declining, however to a lesser extent among men who have sex with men (MSM), and BC is currently experiencing an increase in infectious syphilis cases in this population. These facts reinforce the effectiveness of TasP in decreasing HIV transmission, but at the same time, it highlights the need for further innovation to enhance the control of HIV and syphilis among MSM. This study supports the development of new approaches that address existing gaps in the TasP strategy in BC, and the future health needs of PLWH.

Contact among healthcare workers in the hospital setting: developing the evidence base for innovative approaches to infection control.

BACKGROUND: Nosocomial, or healthcare-associated infections (HAI), exact a high medical and financial toll on patients, healthcare workers, caretakers, and the health system. Interpersonal contact patterns play a large role in infectious disease spread, but little is known about the relationship between health care workers' (HCW) movements and contact patterns within a heath care facility and HAI. Quantitatively capturing these patterns will aid in understanding the dynamics of HAI and may lead to more targeted and effective control strategies in the hospital setting. METHODS: Staff at 3 urban university-based tertiary care hospitals in Canada completed a detailed questionnaire on demographics, interpersonal contacts, in-hospital movement, and infection prevention and control practices. Staff were divided into categories of administrative/support, nurses, physicians, and "Other HCWs" - a fourth distinct category, which excludes physicians and nurses. Using quantitative network modeling tools, we constructed the resulting HCW "co-location network" to illustrate contacts among different occupations and with locations in hospital settings. RESULTS: Among 3048 respondents (response rate 38%) an average of 3.79, 3.69 and 3.88 floors were visited by each HCW each week in the 3 hospitals, with a standard deviation of 2.63, 1.74 and 2.08, respectively. Physicians reported the highest rate of direct patient contacts (> 20 patients/day) but the lowest rate of contacts with other HCWs; nurses had the most extended (> 20 min) periods of direct patient contact. "Other HCWs" had the most direct daily contact with all other HCWs. Physicians also reported significantly more locations visited per week than nurses, other HCW, or administrators; nurses visited the fewest. Public spaces such as the cafeteria had the most staff visits per week, but the least mean hours spent per visit. Inpatient settings had significantly more HCW interactions per week than outpatient settings. CONCLUSIONS: HCW contact patterns and spatial movement demonstrate significant heterogeneity by occupation. Control strategies that address this diversity among health care workers may be more effective than "one-strategy-fits-all" HAI prevention and control programs.

Public health emergency preparedness: a framework to promote resilience.

BACKGROUND: Emergencies and disasters impact population health. Despite the importance of upstream readiness, a persistent challenge for public health practitioners is defining what it means to be prepared. There is a knowledge gap in that existing frameworks lack consideration for complexity relevant to health systems and the emergency context. The objective of this study is to describe the essential elements of a resilient public health system and how the elements interact as a complex adaptive system. METHODS: This study used a qualitative design employing the Structured Interview Matrix facilitation technique in six focus groups across Canada. Focus group participants were practitioners from public health and related sectors. Data collection generated qualitative data on the essential elements, and interactions between elements, for a resilient public health system. Data analysis employed qualitative content analysis and the lens of complexity theory to account for the complex nature of public health emergency preparedness (PHEP). The unit of study was the local/regional public health agency. Ethics and values were considered in the development of the framework. RESULTS: A total of 130 participants attended the six focus groups. Urban, urban-rural and rural regions from across Canada participated and focus group size ranged from 15 to 33 across the six sites. Eleven elements emerged from the data; these included one cross-cutting element (Governance and leadership) and 10 distinct but interlinked elements. The essential elements define a conceptual framework for PHEP. The framework was refined to ensure practice and policy relevance for local/regional public health agencies; the framework has ethics and values at its core. CONCLUSIONS: This framework describes the complexity of the system yet moves beyond description to use tenets of complexity to support building resilience. This applied public health framework for local/regional public health agencies is empirically-derived and theoretically-informed and represents a complex adaptive systems approach to upstream readiness for PHEP.

Outbreak of Vibrio parahaemolyticus Associated with Consumption of Raw Oysters in Canada, 2015.

There has been a steady increase in illness incidence of Vibrio parahaemolyticus (Vp). The majority of illnesses are associated with consumption of raw oysters. In the summer of 2015, Canada experienced the largest outbreak associated with the consumption of raw oysters harvested from British Columbia (BC) coastal waters. Case investigation of laboratory-confirmed cases was conducted to collect information on exposures and to assist traceback. Investigations at processors and oyster sampling were conducted. Eighty-two laboratory-confirmed cases of Vp infection were reported between January 1 and October 26, 2015. The majority of the cases were reported in BC, associated with consumption of raw BC oysters in restaurants. Sea surface temperatures were above the historical levels in 2015. This outbreak identified the need to improve surveillance and response to increases in human cases of Vp. This is of particular importance due to the potential for increasing water temperatures and the likelihood of additional outbreaks of Vibrio.

Characterization of Clostridium difficile Strains in British Columbia, Canada: A Shift from NAP1 Majority (2008) to Novel Strain Types (2013) in One Region.

Background. Clostridium difficile is a major cause of gastrointestinal illness. Epidemic NAP1 strains contain toxins A and B, a deletion in repressor tcdC, and a binary toxin. Objectives. To determine the molecular epidemiology of C. difficile in British Columbia and compare between two time points in one region. Methods. C. difficile isolates from hospital and community laboratories (2008) and one Island Health hospital laboratory (2013) were characterized by pulsed-field gel electrophoresis, PCR-ribotyping, toxin possession, tcdC genotype, and antimicrobial susceptibility. Results. In 2008, 42.7% of isolates had NAP1 designation. Hospital-collected isolates were associated with older patients and more NAP1 types. Unlike other isolates, most NAP1 isolates possessed binary toxin and a 19 bp loss in tcdC. All isolates were susceptible to metronidazole and vancomycin. A 2013 follow-up revealed a 28.9% decrease in NAP1 isolates and 20.0% increase in isolates without NAP designation in one region. Then, community-associated cases were seen in younger patients, while NAP types were evenly distributed. Isolates without NAP designation did not cluster with a PFGE pattern or ribotype. Conclusions. Evaluation of C. difficile infections within British Columbia revealed demographic associations, epidemiological shifts, and characteristics of strain types. Continuous surveillance of C. difficile will enable detection of emerging strains.

Whole-Genome Sequencing of Measles Virus Genotypes H1 and D8 During Outbreaks of Infection Following the 2010 Olympic Winter Games Reveals Viral Transmission Routes.

We used whole-genome sequencing to investigate a dual-genotype outbreak of measles occurring after the XXI Olympic Winter Games in Vancouver, Canada. By sequencing 27 complete genomes from H1 and D8 genotype measles viruses isolated from outbreak cases, we estimated the virus mutation rate, determined that person-to-person transmission is typically associated with 0 mutations between isolates, and established that a single introduction of H1 virus led to the expansion of the outbreak beyond Vancouver. This is the largest measles genomics project to date, revealing novel aspects of measles virus genetics and providing new insights into transmission of this reemerging viral pathogen.

The evidence base of primary research in public health emergency preparedness: a scoping review and stakeholder consultation.

BACKGROUND: Effective public health emergency preparedness and response systems are important in mitigating the impact of all-hazards emergencies on population health. The evidence base for public health emergency preparedness (PHEP) is weak, however, and previous reviews have noted a substantial proportion of anecdotal event reports. To investigate the body of research excluding the anecdotal reports and better understand primary and analytical research for PHEP, a scoping review was conducted with two objectives: first, to develop a thematic map focused on primary research; and second, to use this map to inform and guide an understanding of knowledge gaps relevant to research and practice in PHEP. METHODS: A scoping review was conducted based on established methodology. Multiple databases of indexed and grey literature were searched based on concepts of public health, emergency, emergency management/preparedness and evaluation/evidence. Inclusion and exclusion criteria were applied iteratively. Primary research studies that were evidence-based or evaluative in nature were included in the final group of selected studies. Thematic analysis was conducted for this group. Stakeholder consultation was undertaken for the purpose of validating themes and identifying knowledge gaps. To accomplish this, a purposive sample of researchers and practicing professionals in PHEP or closely related fields was asked to complete an online survey and participate in an in-person meeting. Final themes and knowledge gaps were synthesized after stakeholder consultation. RESULTS: Database searching yielded 3015 citations and article selection resulted in a final group of 58 articles. A list of ten themes from this group of articles was disseminated to stakeholders with the survey questions. Survey findings resulted in four cross-cutting themes and twelve stand-alone themes. Several key knowledge gaps were identified in the following themes: attitudes and beliefs; collaboration and system integration; communication; quality improvement and performance standards; and resilience. Resilience emerged as both a gap and a cross-cutting theme. Additional cross-cutting themes included equity, gender considerations, and high risk or at-risk populations. CONCLUSIONS: In this scoping review of the literature enhanced by stakeholder consultation, key themes and knowledge gaps in the PHEP evidence base were identified which can be used to inform future practice-oriented research in PHEP.

Effectiveness of neuraminidase inhibitors in preventing hospitalization during the H1N1 influenza pandemic in British Columbia, Canada.

OBJECTIVES: In British Columbia (BC), Canada, neuraminidase inhibitors (NIs) were publicly funded during the 2009 A(H1N1)pdm09 pandemic for treatment of high-risk patients and/or anyone with moderate-to-severe illness. We assessed antiviral effectiveness (AVE) against hospitalization in that context. METHODS: A population-based cohort study was conducted using linked administrative data. The cohort included all individuals living in BC during the study period (1 September to 31 December 2009) with a diagnostic code consistent with influenza or pandemic H1N1. The main study period pertained to the second-wave A(H1N1)pdm09 circulation (1 October to 31 December 2009), with sensitivity analyses around the more specific pandemic peak (18 October to 7 November). Exposure was defined by same-day NI prescription. The main outcome was all-cause hospitalization within 14 days of the outpatient influenza diagnosis. Cox proportional hazards models assessed AVE with 1 : 1 propensity-score matching and covariate adjustment. RESULTS: After matching, there were 304/58,061 NI-exposed and 345/58,061 unexposed patients hospitalized during the main study period. The very young [<6 months (35.0; 95% CI 16.7-73.4)], the old [65-79 years (13.7; 95% CI 10.1-18.6)] and the very old [≥80 years (38.7; 95% CI 26.6-56.5)] had the highest hospitalization rate per 1000 patients overall. Fully adjusted AVE against all-cause hospitalization during the main study period was 16% (95% CI 2%-28%), similar to the pandemic peak (15%; 95% CI -4%-30%). CONCLUSIONS: The use of NIs was associated with modest protection against hospitalization during the 2009 pandemic, but appeared underutilized in affected age groups with the highest hospitalization risk.

Estimating the impacts of nonoptimal temperatures on mortality: A study in British Columbia, Canada, 2001-2021.

Background: Studies show that more than 5.1 million deaths annually are attributed to nonoptimal temperatures, including extreme cold and extreme heat. However, those studies mostly report average estimates across large geographical areas. The health risks attributed to nonoptimal temperatures in British Columbia (BC) are reported incompletely or limit the study area to urban centers. In this study, we aim to estimate the attributable deaths linked to nonoptimal temperatures in all five regional health authorities (RHAs) of BC from 2001 to 2021. Methods: We applied the widely used distributed lag nonlinear modeling approach to estimate temperature-mortality association in the RHAs of BC, using daily all-cause deaths and 1 × 1 km gridded daily mean temperature. We evaluated the model by comparing the model-estimated attributable number of deaths during the 2021 heat dome to the number of heat-related deaths confirmed by the British Columbia Coroners Service. Results: Overall, between 2001 and 2021, we estimate that 7.17% (95% empirical confidence interval = 3.15, 10.32) of deaths in BC were attributed to nonoptimal temperatures, the majority of which are attributed to cold. On average, the mortality rates attributable to moderate cold, moderate heat, extreme cold, and extreme heat were 47.04 (95% confidence interval [CI] = 45.83, 48.26), 0.94 (95% CI = 0.81, 1.08), 2.88 (95% CI = 2.05, 3.71), and 3.10 (95% CI = 1.79, 4.4) per 100,000 population per year, respectively. Conclusions: Our results show significant spatial variability in deaths attributable to nonoptimal temperatures across BC. We find that the effect of extreme temperatures is significantly less compared to milder nonoptimal temperatures between 2001 and 2021. However, the increased contribution of extreme heat cannot be ruled out in the near future.

Validation of case definition algorithms for the ascertainment of congenital anomalies.

BACKGROUND: Congenital anomalies (CA) are one of the leading causes of infant mortality and long-term disability. Many jurisdictions rely on health administrative data to monitor these conditions. Case definition algorithms can be used to monitor CA; however, validation of these algorithms is needed to understand the strengths and limitations of the data. This study aimed to validate case definition algorithms used in a CA surveillance system in British Columbia (BC), Canada. METHODS: A cohort of births between March 2000 and April 2002 in BC was linked to the Health Status Registry (HSR) and the BC Congenital Anomalies Surveillance System (BCCASS) to identify cases and non-cases of specific anomalies within each surveillance system. Measures of algorithm performance were calculated for each CA using the HSR as the reference standard. Agreement between both databases was calculated using kappa coefficient. The modified Standards for Reporting Diagnostic Accuracy guidelines were used to enhance the quality of the study. RESULTS: Measures of algorithm performance varied by condition. Positive predictive value (PPV) ranged between approximately 73%-100%. Sensitivity was lower than PPV for most conditions. Internal congenital anomalies or conditions not easily identifiable at birth had the lowest sensitivity. Specificity and negative predictive value exceeded 99% for all algorithms. CONCLUSION: Case definition algorithms may be used to monitor CA at the population level. Accuracy of algorithms is higher for conditions that are easily identified at birth. Jurisdictions with similar administrative data may benefit from using validated case definitions for CA surveillance as this facilitates cross-jurisdictional comparison.

Lyme disease: knowledge, beliefs, and practices of physicians in a low-endemic area.

OBJECTIVE: To determine physicians' level of awareness and knowledge of Lyme disease (LD) in a low-prevalence area and whether physicians' practices align with current guidelines for treatment of LD. DESIGN: A 23-item questionnaire assessing demographic characteristics, general knowledge about LD, laboratory testing for LD, and responses to 3 clinical scenarios. SETTING: British Columbia (BC). PARTICIPANTS: Pediatricians, FPs, and internal medicine specialists who were licensed to practise in BC. MAIN OUTCOME MEASURES: Knowledge of signs and symptoms of LD, beliefs about risk of LD, attitudes toward LD in patients in their practices, and application of accepted practice guidelines for the treatment of LD in clinical scenarios. RESULTS: Overall, 80.6% of respondents were FPs. Average knowledge score was 72.5% for FPs and 75.0% for other specialists. Most respondents (75.6% of FPs and 71.8% of other specialists) underestimated the occurrence of erythema migrans (EM), and only 26.1% and 28.3%, respectively, knew that EM alone was diagnostic for LD. A total of 30.5% of FPs and 12.1% of other specialists reported having treated a patient for the disease despite not believing that the patient had LD. Of all the respondents, 62.1% knew that LD was a reportable disease in BC. Respondents' reports of risk of LD in their areas were appropriately associated with actual risk based on ecological niche. CONCLUSION: Physicians are knowledgeable about the clinical signs and symptoms of LD and aware of the risk of the disease despite being in a low-endemic area. Physicians in BC are comfortable with treating patients empirically for LD. Education is needed to inform physicians that EM is diagnostic and no laboratory testing is indicated before treatment. Raising awareness among physicians that LD is reportable might improve reporting of future cases.

Prion disease risk perception in Canadian medical laboratories.

BACKGROUND: There are no national guidelines specific for handling prion-associated specimens in Canadian medical laboratories. Medical laboratory workers may perceive themselves at risk of prion transmission and, on occasion, decline to process such specimens. OBJECTIVE: To examine the knowledge, attitudes and reported behaviours of medical laboratory workers in relation to prion disease to understand their risk perception and the need for national laboratory guidelines on prion infection control. DESIGN: Survey development and cross-sectional web-based administration. METHODS: The survey was developed through key informant interviews and a modified Delphi process. Medical laboratory workers across Canada were invited by laboratory managers and national organizations to complete the web-based survey. RESULTS: Twelve key informant interviews were performed. Consensus for questionnaire content was reached through two rounds of the Delphi process. Responses were received from 426 Canadian medical laboratory workers; 37% of medical laboratory staff reported processing prion-associated specimens. Different protocols for specimen processing were followed, and 18% believed they were at risk when processing these specimens. Less than one-third of those receiving specimens believed they were adequately trained. The mean (±SD) knowledge score was 9.25±4.5/24; individuals who had received training scored significantly higher than those who were untrained (P<0.01). Eighty-one per cent of respondents would be more comfortable processing specimens if national guidelines existed and were used in their laboratory. CONCLUSION: There is a high perception of risk and few perceived benefits of processing prion-associated specimens. National guidelines for prion infection control in medical laboratories and adequate training would enable medical laboratory workers to process these specimens efficiently and confidently.

HISTORIQUE: Il n'existe pas de lignes directrices nationales propres à la manipulation d'échantillons associés aux infections à prion dans les laboratoires médicaux canadiens. Les travailleurs de ces laboratoires peuvent se percevoir comme vulnérables à la transmission d'une infection à prion et parfois refuser de traiter ces échantillons. OBJECTIF: Examiner les connaissances, les attitudes et les comportements déclarés des travailleurs de laboratoire pour comprendre leur perception du risque et la nécessité de préparer des lignes directrices nationales de laboratoire sur le contrôle des infections à prion. CONCEPTION: Élaboration de l'administration transversale d'un sondage par voie électronique. MÉTHODOLOGIE: Les chercheurs ont préparé le sondage par suite d'entrevues avec des informateurs clés et d'une méthode Delphi modifiée. Des directeurs de laboratoire et des organisations nationales ont invité les travailleurs de laboratoire du Canada à répondre au sondage par voie électronique. RÉSULTATS: Les chercheurs ont effectué 12 entrevues auprès d'informateurs clés. Ils sont parvenus à un consensus quant au contenu du questionnaire après deux rondes de la méthode Delphi. Ils ont reçu la réponse de 426 travailleurs de laboratoire canadiens, dont 37 % déclaraient traiter des échantillons liés à des infections à prion. Divers protocoles de traitement des échantillons étaient respectés, et 18 % des travailleurs se sentaient vulnérables dans le cadre de ce traitement. Moins du tiers des travailleurs qui recevaient ces échantillons se sentaient bien formés pour le faire. L'indice de connaissance moyen s'élevait à 9,25/24 (ÉT±4,5). Les personnes qui avaient reçu une formation obtenaient un indice considérablement plus élevé que celles qui n'en avaient pas reçu (P<0,01). Quatre-vingt-un pour cent des répondants seraient plus à l'aise de traiter les échantillons s'il existait des lignes directrices nationales mises en œuvre dans leur laboratoire. CONCLUSION: La perception du risque est élevée et celle des avantages du traitement des échantillons liés à des infections à prion est faible. Des lignes directrices nationales sur le contrôle des infections à prion dans les laboratoires médicaux et une formation convenable permettraient aux travailleurs de laboratoire de traiter ces échantillons avec efficacité et en toute confiance.

SARS-CoV-2 mRNA Vaccine Effectiveness in Health Care Workers by Dosing Interval and Time Since Vaccination: Test-Negative Design, British Columbia, Canada.

Background: One- and two-dose mRNA vaccine effectiveness (VE) estimates against severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection by dosing interval and time since vaccination were assessed among healthcare workers (HCWs) in publicly funded acute and community (nonresidential) healthcare facilities in British Columbia, Canada. Methods: A test-negative design was used with controls matched to cases (6:1) on epidemiological week of SARS-CoV-2 test date. mRNA vaccination was defined by receipt of the first dose ≥21 days or second dose ≥14 days before the test date. HCWs ≥18 years old tested for SARS-CoV-2 between epi-weeks 3 and 39 (January 17-October 2, 2021) were included, when varying dosing intervals and a mix of circulating variants of concern contributed, including Delta dominance provincially from epi-week 31 (August 1). Results: Single- and two-dose analyses included 1265 and 1246 cases, respectively. The median follow-up period (interquartile range) was 49 (34-69) days for single-dose and 89 (61-123) days for two-dose recipients, with 12%, 31%, and 58% of second doses given 3-5, 6, or ≥7 weeks after the first. Adjusted mRNA VE against SARS-CoV-2 was 71% (95% CI, 66%-76%) for one dose and 90% (95% CI, 88%-92%) for two doses, similar to two heterologous mRNA doses (92%; 95% CI, 86%-95%). Two-dose VE remained >80% at ≥28 weeks post-second dose. Two-dose VE was consistently 5%-7% higher with a ≥7-week vs 3-5-week interval between doses, but with overlapping confidence intervals. Conclusions: Among HCWs, we report substantial single-dose and strong and sustained two-dose mRNA vaccine protection, with the latter maintained for at least 7 months. These findings support a longer interval between doses, with global health and equity implications.