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The tremendous global health burden related to COVID-19 means that identifying determinants of COVID-19 severity is important for prevention and intervention. We aimed to explore long-term exposure to ambient air pollution as a potential contributor to COVID-19 severity, given its known impact on the respiratory system. We used a cohort of all people with confirmed SARS-CoV-2 infection, aged 20 years and older and not residing in a long-term care facility in Ontario, Canada, during 2020. We evaluated the association between long-term exposure to fine particulate matter (PM2.5), nitrogen dioxide (NO2) and ground-level ozone (O3), and risk of COVID-19-related hospital admission, intensive care unit (ICU) admission and death. We ascertained individuals’ long-term exposures to each air pollutant based on their residence from 2015 to 2019. We used logistic regression and adjusted for confounders and selection bias using various individual and contextual covariates obtained through data linkage. Among the 151 105 people with confirmed SARS-CoV-2 infection in Ontario in 2020, we observed 8630 hospital admissions, 1912 ICU admissions and 2137 deaths related to COVID-19. For each interquartile range increase in exposure to PM2.5 (1.70 μg/m3), we estimated odds ratios of 1.06 (95% confidence interval [CI] 1.01–1.12), 1.09 (95% CI 0.98–1.21) and 1.00 (95% CI 0.90–1.11) for hospital admission, ICU admission and death, respectively. Estimates were smaller for NO2. We also estimated odds ratios of 1.15 (95% CI 1.06–1.23), 1.30 (95% CI 1.12–1.50) and 1.18 (95% CI 1.02–1.36) per interquartile range increase of 5.14 ppb in O3 for hospital admission, ICU admission and death, respectively. Chronic exposure to air pollution may contribute to severe outcomes after SARS-CoV-2 infection, particularly exposure to O3.

Background Almost 1% of Canadians are hepatitis C (HCV)-infected. The liver-specific complications of HCV are established but the extra-hepatic comorbidity, multimorbidity, and its relationship with HCV treatment, is less well known. We describe the morbidity burden for people with HCV and the relationship between multimorbidity and HCV treatment uptake and cure in the pre- and post-direct acting antiviral (DAA) era. Methods We linked adults with HCV at The Ottawa Hospital Viral Hepatitis Program as of April 1, 2017 to provincial health administrative data and matched on age and sex to 5 Ottawa-area residents for comparison. We used validated algorithms to identify the prevalence of mental and physical health comorbidities, as well as multimorbidity (2+ comorbidities). We calculated direct age- and sex-standardized rates of comorbidity and comparisons were made by interferon-based and interferon-free, DAA HCV treatments. Results The mean age of the study population was 54.5 years (SD 11.4), 65% were male. Among those with HCV, 4% were HIV co-infected, 26% had liver cirrhosis, 47% received DAA treatment, and 57% were cured of HCV. After accounting for age and sex differences, the HCV group had greater multimorbidity (prevalence ratio (PR) 1.38, 95% confidence interval (CI) 1.20 to 1.58) and physical-mental health multimorbidity (PR 2.71, 95% CI 2.29–3.20) compared to the general population. Specifically, prevalence ratios for people with HCV were significantly higher for diabetes, renal failure, cancer, asthma, chronic obstructive pulmonary disease, substance use disorder, mood and anxiety disorders and liver failure. HCV treatment and cure were not associated with multimorbidity, but treatment prevalence was significantly lower among middle-aged individuals with substance use disorders despite no differences in prevalence of cure among those treated. Conclusion People with HCV have a higher prevalence of comorbidity and multimorbidity compared to the general population. While HCV treatment was not associated with multimorbidity, people with substance use disorder were less likely to be treated. Our results point to the need for integrated, comprehensive models of care delivery for people with HCV.

We describe our experiences with identifying and recruiting Ontario parents through the Internet, primarily, as well as other modes, for participation in focus groups about adding the influenza vaccine to school-based immunization programs. Our objectives were to assess participation rates with and without incentives and software restrictions. We also plan to examine study response patterns of unique and multiple submissions and assess efficiency of each online advertising mode. We used social media, deal forum websites, online classified ads, conventional mass media, and email lists to invite parents of school-aged children from Ontario, Canada to complete an online questionnaire to determine eligibility for focus groups. We compared responses and paradata when an incentive was provided and there were no software restrictions to the questionnaire (Period 1) to a period when only a single submission per Internet protocol (IP) address (ie, software restrictions invoked) was permitted and no incentive was provided (Period 2). We also compared the median time to complete a questionnaire, response patterns, and percentage of missing data between questionnaires classified as multiple submissions from the same Internet protocol (IP) address or email versus unique submissions. Efficiency was calculated as the total number of hours study personnel devoted to an advertising mode divided by the resultant number of unique eligible completed questionnaires . Of 1346 submitted questionnaires, 223 (16.6%) were incomplete and 34 (2.52%) did not meet the initial eligibility criteria. Of the remaining 1089 questionnaires, 246 (22.6%) were not from Ontario based on IP address and postal code, and 469 (43.1%) were submitted from the same IP address or email address (multiple submissions). In Period 2 vs Period 1, a larger proportion of questionnaires were submitted from Ontario (92.8%, 141/152 vs 75.1%, 702/937, P<.001), and a smaller proportion of same IP addresses (7.9%, 12/152 vs 47.1%, 441/937, P<.001) were received. Compared to those who made unique submissions, those who made multiple submissions spent less time per questionnaire (166 vs 215 seconds, P<.001), and had a higher percentage of missing data among their responses (15.0% vs 7.6%, P=.004). Advertisements posted on RedFlagDeals were the most efficient for recruitment (0.03 hours of staff time per questionnaire), whereas those placed on Twitter were the least efficient (3.64 hours of staff time per questionnaire). Using multiple online advertising strategies was effective for recruiting a large sample of participants in a relatively short period time with minimal resources. However, risks such as multiple submissions and potentially fraudulent information need to be considered. In our study, these problems were associated with providing an incentive for responding, and could have been partially avoided by activating restrictive software features for online questionnaires.

Objectives. We compared seasonal influenza hospital use among older adults in long-term care (LTC) and community settings. Methods. We used provincial administrative data from Ontario to identify all emergency department (ED) visits and hospital admissions for pneumonia and influenza among adults older than 65 years between 2002 and 2008. We used sentinel laboratory reports to define influenza and summer seasons and estimated mean annual event rates and influenza-associated rates. Results. Mean annual pneumonia and influenza ED visit rates were higher in LTC than the community (rate ratio [RR] for influenza season = 3.9; 95% confidence interval [CI] = 3.8, 4.0; for summer = 4.9; 95% CI = 4.8, 5.1) but this was attenuated in influenza-associated rates (RR = 2.4; 95% CI = 2.1, 2.8). The proportion of pneumonia and influenza ED visits attributable to seasonal influenza was 17% (15%–20%) in LTC and 28% (27%–29%) in the community. Results for hospital admissions were comparable. Conclusions. We found high rates of hospital use from LTC but evidence of lower impact of circulating influenza in the community. This differential impact of circulating influenza between the 2 environments may result from different influenza control policies.

This article reports recent trends in influenza vaccination rates in Canada, provides data on predictors of vaccination in Canada for 2005, and examines longer-term effects of Ontario's universal influenza immunization program on vaccine uptake. Data are from the 1996/1997 National Population Health Survey (NPHS) and the 2000/2001, 2003, and 2005 Canadian Community Health Survey (CCHS). NPHS and CCHS data were used to estimate influenza vaccination rates of the population aged 12 or older. The Z test was used to assess differences between surveys, and the chi-squared test for trend was used to examine trends over time. Logistic regression was used to identify predictors of vaccination and to compare the odds of being vaccinated in Ontario versus other provinces. Nationally, influenza vaccination rates rose from 15% in 1996/1997 to 27% in 2000/2001, stabilized between 2000/2001 and 2003, and increased further to 34% by 2005. Vaccination rates for most high-risk groups still fall short of national targets. Ontarians continue to be more likely to be vaccinated than are residents of any other province, while residents of two of the territories--Nunavut and the Northwest Territories--are even more likely to be vaccinated than are Ontarians.

The demographic and socioeconomic profile of medical school classes has implications for where people choose to practise and whether they choose to treat certain disadvantaged groups. We aimed to describe the demographic and socioeconomic characteristics of first-year Canadian medical students and compare them with those of the Canadian population to determine whether there are groups that are over- or underrepresented. Furthermore, we wished to test the hypothesis that medical students often come from privileged socioeconomic backgrounds. As part of a larger Internet survey of all students at Canadian medical schools outside Quebec, conducted in January and February 2001, first-year students were asked to give their age, sex, self-described ethnic background using Statistics Canada census descriptions and educational background. Postal code at the time of high school graduation served as a proxy for socioeconomic status. Respondents were also asked for estimates of parental income and education. Responses were compared when possible with Canadian age-group-matched data from the 1996 census. Responses were obtained from 981 (80.2%) of 1223 first-year medical students. There were similar numbers of male and female students (51.1% female), with 65% aged 20 to 24 years. Although there were more people from visible minorities in medical school than in the Canadian population (32.4% v. 20.0%) (p < 0.001), certain minority groups (black and Aboriginal) were underrepresented, and others (Chinese, South Asian) were overrepresented. Medical students were less likely than the Canadian population to come from rural areas (10.8% v. 22.4%) (p< 0.001) and were more likely to have higher socioeconomic status, as measured by parents' education (39.0% of fathers and 19.4% of mothers had a master's or doctoral degree, as compared with 6.6% and 3.0% respectively of the Canadian population aged 45 to 64), parents' occupation (69.3% of fathers and 48.7% of mothers were professionals or high-level managers, as compared with 12.0% of Canadians) and household income (15.4% of parents had annual household incomes less than $40,000, as compared with 39.7% of Canadian households; 17.0% of parents had household incomes greater than $160,000, as compared with 2.7% of Canadian households with an income greater than $150,000). Almost half (43.5%) of the medical students came from neighbourhoods with median family incomes in the top quintile (p < 0.001). A total of 57.7% of the respondents had completed 4 years or less of postsecondary studies before medical school, and 29.3% had completed 6 or more years. The parents of the medical students tended to have occupations with higher social standing than did working adult Canadians; a total of 15.6% of the respondents had a physician parent. Canadian medical students differ significantly from the general population, particularly with regard to ethnic background and socioeconomic status.

The Global COVID Vaccine Safety (GCoVS) project was established in 2021 under the multinational Global Vaccine Data Network (GVDN) consortium to facilitate the rapid assessment of the safety of newly introduced vaccines. This study analyzed data from GVDN member sites on the background incidence rates of conditions designated as adverse events of special interest (AESI) for COVID-19 vaccine safety monitoring. Eleven GVDN global sites obtained data from national or regional healthcare databases using standardized methods. Incident events of 13 pre-defined AESI were included for a pre-pandemic period (2015–19) and the first pandemic year (2020). Background incidence rates (IR) and 95% confidence intervals (CI) were calculated for inpatient and emergency department encounters, stratified by age and sex, and compared between pre-pandemic and pandemic periods using incidence rate ratios. An estimated 197 million people contributed 1,189,652,926 person-years of follow-up time. Among inpatients in the pre-pandemic period (2015–19), generalized seizures were the most common neurological AESI (IR ranged from 22.15 [95% CI 19.01–25.65] to 278.82 [278.20–279.44] per 100,000 person-years); acute disseminated encephalomyelitis was the least common (<0.5 per 100,000 person-years at most sites). Pulmonary embolism was the most common thrombotic event (IR 45.34 [95% CI 44.85–45.84] to 93.77 [95% CI 93.46–94.08] per 100,000 person-years). The IR of myocarditis ranged from 1.60 [(95% CI 1.45–1.76) to 7.76 (95% CI 7.46–8.08) per 100,000 person-years. The IR of several AESI varied by site, healthcare setting, age and sex. The IR of some AESI were notably different in 2020 compared to 2015–19. Background incidence of AESIs exhibited some variability across study sites and between pre-pandemic and pandemic periods. These findings will contribute to global vaccine safety surveillance and research.

Hepatitis C virus (HCV) has high global prevalence and can lead to liver complications and death. Access to direct-acting antivirals (DAAs) in Canada increased following several policy changes, however the real-world impact of expanded DAA access and increased use of these drugs is unknown. We aimed to determine the early change in rates of HCV-related hospitalizations overall and HCV-related hospitalizations with hepatocellular carcinoma (HCC) after expanded DAA access. We conducted a population-based time series analysis using national administrative health databases in Canada. Rates of HCV-related hospitalizations and HCV-related hospitalizations with HCC were enumerated monthly between April 2006 and March 2020. We used Autoregressive Integrated Moving Average (ARIMA) models with ramp functions in October 2014 and January 2017 to evaluate the impact of policies to expand DAA access on hospitalization outcomes. Rates of HCV-related hospitalizations in Canada increased between 2006 and 2014, and gradually declined thereafter. The decrease after October 2014, or the first policy change, was significant (p = 0.0355), but no further change was found after the second policy change in 2017 (p = 0.2567). HCV-related hospitalizations with HCC increased until end of 2013, followed by a plateau, before declining in 2016. No significant shifts were found after the first policy change in 2014 (p = 0.1291) nor the second policy change in 2017 (p = 0.6324). Subgroup analyses revealed that those aged 50-64 and males had observable declines in rates of HCV-related hospitalizations in the year prior to the first policy change. Expanding DAA access was associated with a drop in HCV-related hospitalizations in the overall Canadian population coinciding with the 2014 policy change. In light of the time required for HCV-related complications to manifest, continued ongoing research examining the real-world effectiveness of DAAs is required.

Since 1997, tuition has more than doubled at Ontario medical schools but has remained relatively stable in other Canadian provinces. We sought to determine whether the increasing tuition fees in Ontario affected the demographic characteristics and financial outlook of medical students in that province as compared with those of medical students in the rest of Canada. As part of a larger Internet survey of all students at Canadian medical schools outside Quebec, conducted in January and February 2001, we compared the respondents from Ontario schools with those from the other schools (control group). Respondents were asked about their age, sex, self-reported family income (as a direct indicator of socioeconomic status), the first 3 digits of their postal code at graduation from high school (as an indirect indicator of socioeconomic status), and importance of financial considerations in choosing a specialty and location of practice. We used logistic regression models to see if temporal changes (1997 v. 2000) among Ontario medical students differed from those among medical students elsewhere in Canada apart from Quebec. Responses were obtained from 2994 (68.5%) of 4368 medical students. Across the medical schools, there was an increase in self-reported family income between 1997 and 2000 (p = 0.03). In Ontario, the proportion of respondents with a family income of less than $40,000 declined from 22.6% to 15.0%. However, compared with the control respondents, the overall rise in family income among Ontario students was not statistically significant. First-year Ontario students reported higher levels of expected debt at graduation than did graduating students (median $80,000 v. $57,000) (p < 0.001), and the proportion of students expecting to graduate with debt of at least $100,000 more than doubled. Neither of these differences was observed in the control group. First-year Ontario students were also more likely than fourth-year Ontario students to report that their financial situation was \"very\" or \"extremely\" stressful and to cite financial considerations as having a major influence on specialty choice or practice location. These differences were not observed in the control group. At Canadian medical schools, there are fewer students from low-income families in general. However, Ontario medical students report a large increase in expected debt on graduation, an increased consideration of finances in deciding what or where to practise, and increasing financial stress, factors that are not observed among students in other provinces.

This article examines the association between introduction of Ontario's Universal Influenza Immunization Program and changes in vaccination rates over time in Ontario, compared with the other provinces combined. The data are from the 1996/97 National Population Health Survey and the 2000/01 and 2003 Canadian Community Health Survey, both conducted by Statistics Canada. Cross-tabulations were used to estimate vaccination rates for the total population aged 12 or older, for groups especially vulnerable to the effects of influenza, and by selected socio-demographic variables. Z tests and multiple logistic regression were used to examine differences between estimates. Between 1996/97 and 2000/01, the increase in the overall vaccination rate in Ontario was 10 percentage points greater than the increase in the other provinces combined. Increases in Ontario were particularly pronounced among people who were: younger than 65, more educated, and had a higher household income. Between 2000/01 and 2003, vaccination rates were stable in Ontario, while rates continued to rise in the other provinces. Even so, Ontario's 2003 rates exceeded those in the other provinces.