Effectiveness of Coronavirus Disease 2019 Vaccines Against Hospitalization and Death in Canada: A Multiprovincial, Test-Negative Design Study.

BACKGROUND: A major goal of coronavirus disease 2019 (COVID-19) vaccination is to prevent severe outcomes (hospitalizations and deaths). We estimated the effectiveness of messenger RNA (mRNA) and ChAdOx1 COVID-19 vaccines against severe outcomes in 4 Canadian provinces between December 2020 and September 2021. METHODS: We conducted this multiprovincial, retrospective, test-negative study among community-dwelling adults aged ≥18 years in Ontario, Quebec, British Columbia, and Manitoba using linked provincial databases and a common study protocol. Multivariable logistic regression was used to estimate province-specific vaccine effectiveness against COVID-19 hospitalization and/or death. Estimates were pooled using random-effects models. RESULTS: We included 2 508 296 tested participants, with 31 776 COVID-19 hospitalizations and 5842 deaths. Vaccine effectiveness was 83% after a first dose and 98% after a second dose against both hospitalization and death (separately). Against severe outcomes, effectiveness was 87% (95% confidence interval [CI], 71%-94%) ≥84 days after a first dose of mRNA vaccine, increasing to 98% (95% CI, 96%-99%) ≥112 days after a second dose. Vaccine effectiveness against severe outcomes for ChAdOx1 was 88% (95% CI, 75%-94%) ≥56 days after a first dose, increasing to 97% (95% CI, 91%-99%) ≥56 days after a second dose. Lower 1-dose effectiveness was observed for adults aged ≥80 years and those with comorbidities, but effectiveness became comparable after a second dose. Two doses of vaccines provided very high protection for both homologous and heterologous schedules and against Alpha, Gamma, and Delta variants. CONCLUSIONS: Two doses of mRNA or ChAdOx1 vaccine provide excellent protection against severe outcomes.

Risk of Severe COVID-19-Related Outcomes among Patients with Cirrhosis: A Population-Based Cohort Study in Canada.

We assessed the association between cirrhosis and severe COVID-19-related outcomes among people with laboratory-diagnosed COVID-19 infection in British Columbia, Canada. We used data from the British Columbia (BC) COVID-19 Cohort, a population-based cohort that integrates data on all individuals tested for COVID-19, with data on hospitalizations, medical visits, emergency room visits, prescription drugs, chronic conditions, and deaths in the Canadian province of BC. We included all individuals aged ≥18 who tested positive for SARS-CoV-2 by real-time reverse transcription-polymerase chain reaction from 1 January 2021 to 31 December 2021. Multivariable logistic regression models were used to assess the associations of cirrhosis status with COVID-19-related hospitalization and with ICU admission. Of the 162,509 individuals who tested positive for SARS-CoV-2 and were included in the analysis, 768 (0.5%) had cirrhosis. In the multivariable models, cirrhosis was associated with increased odds of hospitalization (aOR = 1.97, 95% CI: 1.58-2.47) and ICU admission (aOR = 3.33, 95% CI: 2.56-4.35). In the analyses stratified by age, we found that the increased odds of ICU admission among people with cirrhosis were present in all the assessed age-groups. Cirrhosis is associated with increased odds of hospitalization and ICU admission among COVID-19 patients.

Risk of Major Adverse Cardiovascular Events After SARS-CoV-2 Infection in British Columbia: A Population-Based Study.

BACKGROUND: COVID-19 is associated with increased risk of post-acute cardiovascular outcomes. Population-based evidence for long periods of observation is still limited. METHODS: This population-based cohort study was conducted using data (2020-2021) from the British Columbia COVID-19 Cohort. The exposure of interest was severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection, identified through reverse transcription-polymerase chain reaction (RT-PCR) assay. Individuals who tested positive (exposed) on RT-PCR were matched to negative controls (unexposed) on sex, age, and RT-PCR collection date in a 1:4 ratio. Outcomes of interest were incident major adverse cardiovascular events and acute myocardial infarction, identified more than 30 days after RT-PCR collection date. The association between SARS-CoV-2 infection and cardiovascular risk was assessed through multivariable survival models. Population attributable fractions were computed from Cox models. RESULTS: We included 649,320 individuals: 129,864 exposed and 519,456 unexposed. The median duration of follow-up was 260 days; 1,786 events (0.34%) took place among the unexposed, and 702 (0.54%) in the exposed. The risk of major adverse cardiovascular events was higher in the exposed (adjusted hazard ratio [aHR] 1.34; 95% confidence interval [CI], 1.22-1.46), with greater risk observed in those who were hospitalized (aHR 3.81; 95% CI, 3.12-4.65) or required intensive care unit admission (aHR 6.25; 95% CI, 4.59-8.52) compared with the unexposed group. The fraction of cardiovascular events attributable to SARS-CoV-2 was 7.04% (95% CI, 4.67-9.41%). Comparable results were observed for acute myocardial infarction. CONCLUSIONS: SARS-CoV-2 infection was associated with higher cardiovascular risk, with graded increase across the acute COVID-19 severity, contributing to 7% of incident major adverse cardiovascular events. These findings suggest that long-term monitoring of cardiovascular risk is required in COVID-19 survivors.

Treatment of HCV with direct-acting antivirals on reducing mortality related to extrahepatic manifestations: a large population-based study in British Columbia, Canada.

Background: HCV infection is associated with mortality due to extrahepatic manifestations (EHM). Sustained virologic response (SVR) following direct-acting antiviral (DAA) therapy has been linked to decreased all-cause and liver-related mortality. However, evidence regarding the impact of DAA on EHM-related deaths is lacking. This study aimed to assess the impact of DAA and SVR on EHM-related mortality. Methods: The British Columbia Hepatitis Testers Cohort comprises ∼1.7 million people tested for HCV between 1990 and 2015 and is linked with administrative health data. Among individuals diagnosed with HCV by 12/31/2020, those who received at least one DAA treatment were matched to those who never received treatment by the year of their first HCV RNA positive date. We compared three groups: treated & SVR, treated & no-SVR, and untreated; and generated EHM mortality rates and incidence curves. To account for differences in baseline characteristics, we used inverse probability of treatment weights (IPTW). IPTW-weighted multivariable cause-specific Cox regression models were adjusted for competing risk and confounders. Findings: Study population included 12,815 treated (12,287 SVR, 528 no-SVR) and 12,815 untreated individuals (median follow-up 3.4 years, IQR 2.9). The untreated group had the highest EHM mortality rate (30.9 per 1000 person-years [PY], 95% CI 29.2-32.8), followed by the treated & no-SVR group (21.2 per 1000 PY, 95% CI 14.9-30.1), while the treated & SVR group had the lowest EHM mortality rate (7.9 per 1000 PY, 95% CI 7.1-8.7). In the multivariable model, EHM mortality in the treated & SVR group was significantly decreased (adjusted cause-specific hazard ratio [acsHR] 0.20, 95% CI 0.18-0.23). The treated & SVR group had significant reductions in mortality related to each of the EHMs (78-84%). Interpretation: Treatment of HCV with DAA was associated with significant reductions in EHM-related mortality. These findings emphasize the critical importance of timely diagnosis and treatment of HCV to prevent deaths associated with EHM, and have important implications for clinical practice and public health. Funding: This work was supported by the BC Centre for Disease Control and the Canadian Institutes of Health Research (CIHR) [Grant # NHC-348216, PJT-156066, and PHE-337680]. DJ has received Doctoral Research Award (#201910DF1-435705-64343) from the Canadian Institutes of Health Research (CIHR) and Doctoral fellowship from the Canadian Network on Hepatitis C (CanHepC). CanHepC is funded by a joint initiative of the Canadian Institutes of Health Research (CIHR) (NHC-142832) and the Public Health Agency of Canada (PHAC).

Cohort profile: the British Columbia COVID-19 Cohort (BCC19C)-a dynamic, linked population-based cohort.

Purpose: The British Columbia COVID-19 Cohort (BCC19C) was developed from an innovative, dynamic surveillance platform and is accessed/analyzed through a cloud-based environment. The platform integrates recently developed provincial COVID-19 datasets (refreshed daily) with existing administrative holdings and provincial registries (refreshed weekly/monthly). The platform/cohort were established to inform the COVID-19 response in near "real-time" and to answer more in-depth epidemiologic questions. Participants: The surveillance platform facilitates the creation of large, up-to-date analytic cohorts of people accessing COVID-19 related services and their linked medical histories. The program of work focused on creating/analyzing these cohorts is referred to as the BCC19C. The administrative/registry datasets integrated within the platform are not specific to COVID-19 and allow for selection of "control" individuals who have not accessed COVID-19 services. Findings to date: The platform has vastly broadened the range of COVID-19 analyses possible, and outputs from BCC19C analyses have been used to create dashboards, support routine reporting and contribute to the peer-reviewed literature. Published manuscripts (total of 15 as of July, 2023) have appeared in high-profile publications, generated significant media attention and informed policy and programming. In this paper, we conducted an analysis to identify sociodemographic and health characteristics associated with receiving SARS-CoV-2 laboratory testing, testing positive, and being fully vaccinated. Other published analyses have compared the relative clinical severity of different variants of concern; quantified the high "real-world" effectiveness of vaccines in addition to the higher risk of myocarditis among younger males following a 2nd dose of an mRNA vaccine; developed and validated an algorithm for identifying long-COVID patients in administrative data; identified a higher rate of diabetes and healthcare utilization among people with long-COVID; and measured the impact of the pandemic on mental health, among other analyses. Future plans: While the global COVID-19 health emergency has ended, our program of work remains robust. We plan to integrate additional datasets into the surveillance platform to further improve and expand covariate measurement and scope of analyses. Our analyses continue to focus on retrospective studies of various aspects of the COVID-19 pandemic, as well as prospective assessment of post-acute COVID-19 conditions and other impacts of the pandemic.

A population-based assessment of myocarditis after messenger RNA COVID-19 booster vaccination among adult recipients.

OBJECTIVES: We aimed to estimate the rate of myocarditis after the messenger RNA (mRNA) COVID-19 booster vaccination by vaccine type, age, and sex. METHODS: We used data from the British Columbia COVID-19 Cohort, a population-based cohort surveillance platform. The exposure was a booster dose of an mRNA vaccine. The outcome was diagnosis of myocarditis during hospitalization or an emergency department visit within 7-21 days of booster vaccination. RESULTS: The overall rate of myocarditis was lower for the booster dose (6.41, 95% confidence interval [CI]: 3.50-10.75) than the second dose (17.97, 95% CI: 13.78-23.04); (Rate ratiobooster vs dose-2 = 0.34, 95% CI: 0.17-0.61). This difference was more apparent for the mRNA-1273 vaccine type. After the second dose, the myocarditis rate in males was significantly lower for BNT162b2 than mRNA-1273 overall and among those aged 18-39 years. In contrast, after the booster dose, no significant differences between myocarditis and vaccine type was observed overall or within the specific age groups among males or females. CONCLUSION: Myocarditis after mRNA COVID-19 vaccines is a rare event. A lower absolute risk of myocarditis was observed after a booster dose of mRNA vaccine than the primary series second dose.

The Impact of Mask Mandates on Face Mask Use During the COVID-19 Pandemic: Longitudinal Survey Study.

BACKGROUND: Face mask use has been associated with declines in COVID-19 incidence rates worldwide. A handful of studies have examined the factors associated with face mask use in North America during the COVID-19 pandemic; however, much less is known about the patterns of face mask use and the impact of mask mandates during this time. This information could have important policy implications, now and in the event of future pandemics. OBJECTIVE: To address existing knowledge gaps, we assessed face mask usage patterns among British Columbia COVID-19 Population Mixing Patterns (BC-Mix) survey respondents and evaluated the impact of the provincial mask mandate on these usage patterns. METHODS: Between September 2020 and July 2022, adult British Columbia residents completed the web-based BC-Mix survey, answering questions on the circumstances surrounding face mask use or lack thereof, movement patterns, and COVID-19-related beliefs. Trends in face mask use over time were assessed, and associated factors were evaluated using multivariable logistic regression. A stratified analysis was done to examine effect modification by the provincial mask mandate. RESULTS: Of the 44,301 respondents, 81.9% reported wearing face masks during the 23-month period. In-store and public transit mask mandates supported monthly face mask usage rates of approximately 80%, which was further bolstered up to 92% with the introduction of the provincial mask mandate. Face mask users mostly visited retail locations (51.8%) and travelled alone by car (49.6%), whereas nonusers mostly traveled by car with others (35.2%) to their destinations-most commonly parks (45.7%). Nonusers of face masks were much more likely to be male than female, especially in retail locations and restaurants, bars, and cafés. In a multivariable logistic regression model adjusted for possible confounders, factors associated with face mask use included age, ethnicity, health region, mode of travel, destination, and time period. The odds of face mask use were 3.68 times greater when the provincial mask mandate was in effect than when it was not (adjusted odds ratio [aOR] 3.68, 95% CI 3.33-4.05). The impact of the mask mandate was greatest in restaurants, bars, or cafés (mandate: aOR 7.35, 95% CI 4.23-12.78 vs no mandate: aOR 2.81, 95% CI 1.50-5.26) and in retail locations (mandate: aOR 19.94, 95% CI 14.86-26.77 vs no mandate: aOR 7.71, 95% CI 5.68-10.46). CONCLUSIONS: Study findings provide added insight into the dynamics of face mask use during the COVID-19 pandemic. Mask mandates supported increased and sustained high face mask usage rates during the first 2 years of the pandemic, having the greatest impact in indoor public locations with limited opportunity for physical distancing targeted by these mandates. These findings highlight the utility of mask mandates in supporting high face mask usage rates during the COVID-19 pandemic.

Impact of Hepatitis B Virus Infection, Non-alcoholic Fatty Liver Disease, and Hepatitis C Virus Co-infection on Liver-Related Death among People Tested for Hepatitis B Virus in British Columbia: Results from a Large Longitudinal Population-Based Cohort Study.

Data on the contribution of hepatitis B virus (HBV) infection and related comorbidities to liver-related mortality in Canada are limited. We assessed the concurrent impact of HBV infection, non-alcoholic fatty liver disease (NAFLD), and hepatitis C virus (HCV) coinfection on liver-related deaths in British Columbia (BC), Canada. We used data from the BC Hepatitis Testers Cohort (BC-HTC). We used Fine-Gray multivariable sub-distributional hazards models to assess the effect of HBV, NAFLD, and HCV coinfection on liver-related mortality, while adjusting for confounders and competing mortality risks. The liver-related mortality rate was higher among people with HBV infection than those without (2.57 per 1000 PYs (95%CI: 2.46, 2.69) vs. 0.62 per 1000 PYs (95%CI: 0.61, 0.64), respectively). Compared with the HBV negative groups, HBV infection was associated with increased liver-related mortality risk in almost all of the subgroups: HBV mono-infection (adjusted subdistribution hazards ratio (asHR) of 3.35, 95% CI 3.16, 3.55), NAFLD with HBV infection, (asHR 12.5, 95% CI 7.08, 22.07), and HBV/HCV coinfection (asHR 8.4, 95% CI 7.62, 9.26). HBV infection is associated with a higher risk of liver-related mortality, and has a greater relative impact on people with NAFLD and those with HCV coinfection. The diagnosis and treatment of viral and fatty liver disease are required to mitigate liver-related morbidity and mortality.

Mental Health and Substance Use Associated with Hospitalization among People with COVID-19: A Population-Based Cohort Study.

This study identified factors associated with hospital admission among people with laboratory-diagnosed COVID-19 cases in British Columbia. The study used data from the BC COVID-19 Cohort, which integrates data on all COVID-19 cases with data on hospitalizations, medical visits, emergency room visits, prescription drugs, chronic conditions and deaths. The analysis included all laboratory-diagnosed COVID-19 cases in British Columbia to 15 January 2021. We evaluated factors associated with hospital admission using multivariable Poisson regression analysis with robust error variance. Of the 56,874 COVID-19 cases included in the analysis, 2298 were hospitalized. Factors associated with increased hospitalization risk were as follows: male sex (adjusted risk ratio (aRR) = 1.27; 95% CI = 1.17-1.37), older age (p-trend < 0.0001 across age groups increasing hospitalization risk with increasing age [aRR 30-39 years = 3.06; 95% CI = 2.32-4.03, to aRR 80+ years = 43.68; 95% CI = 33.41-57.10 compared to 20-29 years-old]), asthma (aRR = 1.15; 95% CI = 1.04-1.26), cancer (aRR = 1.19; 95% CI = 1.09-1.29), chronic kidney disease (aRR = 1.32; 95% CI = 1.19-1.47), diabetes (treated without insulin aRR = 1.13; 95% CI = 1.03-1.25, requiring insulin aRR = 5.05; 95% CI = 4.43-5.76), hypertension (aRR = 1.19; 95% CI = 1.08-1.31), injection drug use (aRR = 2.51; 95% CI = 2.14-2.95), intellectual and developmental disabilities (aRR = 1.67; 95% CI = 1.05-2.66), problematic alcohol use (aRR = 1.63; 95% CI = 1.43-1.85), immunosuppression (aRR = 1.29; 95% CI = 1.09-1.53), and schizophrenia and psychotic disorders (aRR = 1.49; 95% CI = 1.23-1.82). In an analysis restricted to women of reproductive age, pregnancy (aRR = 2.69; 95% CI = 1.42-5.07) was associated with increased risk of hospital admission. Older age, male sex, substance use, intellectual and developmental disability, chronic comorbidities, and pregnancy increase the risk of COVID-19-related hospitalization.

Impact of HCV infection and ethnicity on incident type 2 diabetes: findings from a large population-based cohort in British Columbia.

INTRODUCTION: Increasing evidence indicates that chronic hepatitis C virus (HCV) infection is associated with higher risk of diabetes. Previous studies showed ethnic disparities in the disease burden of diabetes, with increased risk in Asian population. We described the incidence of type 2 diabetes related to HCV infection and assessed the concurrent impact of HCV infection and ethnicity on the risk of diabetes. RESEARCH DESIGN AND METHODS: In British Columbia Hepatitis Testers Cohort, individuals were followed from HCV diagnosis to the earliest of (1) incident type 2 diabetes, (2) death or (3) end of the study (December 31, 2015). Study population included 847 021 people. Diabetes incidence rates in people with and without HCV were computed. Propensity scores (PS) analysis was used to assess the impact of HCV infection on newly acquired diabetes. PS-matched dataset included 117 184 people. We used Fine and Gray multivariable subdistributional hazards models to assess the effect of HCV and ethnicity on diabetes while adjusting for confounders and competing risks. RESULTS: Diabetes incidence rates were higher among people with HCV infection than those without. The highest diabetes incidence rate was in South Asians with HCV (14.7/1000 person-years, 95% CI 12.87 to 16.78). Compared with Others, South Asians with and without HCV and East Asians with HCV had a greater risk of diabetes. In the multivariable stratified analysis, HCV infection was associated with increased diabetes risk in all subgroups: East Asians, adjusted HR (aHR) 3.07 (95% CI 2.43 to 3.88); South Asians, aHR 2.62 (95% CI 2.10 to 3.26); and Others, aHR 2.28 (95% CI 2.15 to 2.42). CONCLUSIONS: In a large population-based linked administrative health data, HCV infection was associated with higher diabetes risk, with a greater relative impact in East Asians. South Asians had the highest risk of diabetes. These findings highlight the need for care and screening for HCV-related chronic diseases such as type 2 diabetes among people affected by HCV.