Jeffrey C. Kwong’s research while affiliated with University of Toronto and other places

Knowledge of patterns in COVID-19 deaths by area-level income over time and the mediating role of vaccination in inequality patterns remains limited. We used data from a population-based retrospective cohort of 11,248,572 adults in Ontario, Canada. Cause-specific hazard models were used examine the relationship between income 2016 Census at the dissemination area level) and COVID-19 deaths between March-1-2020 and January-30-2022, stratified by wave. We used regression-based causal mediation analyses to examine the mediating role of vaccination in the relationship between income and COVID-19 deaths during waves4 & 5. After accounting for demographics, baseline health, and other social determinants of health, inequalities in COVID-19 deaths by income persisted over time (hazard ratios[95% confidence intervals] comparing lowest-income vs. highest-income quintiles were 1.37[0.98-1.92] for wave-1, 1.21[0.99-1.48] for wave-2, 1.55[1.22-1.96] for wave-3, and 1.57[1.15-2.15] for waves4 & 5). By the start of wave four, 7,534,259(67.7%) of those alive were vaccinated, with lower odds of vaccination in the lowest-income vs. highest-income quintiles (0.71[0.70-0.71]). This inequality in vaccination accounted for 56.9%[22.5%-91.3%] of inequalities in COVID-19 deaths between individuals in the lowest-income vs. highest-income quintiles. Efforts are needed to address vaccination gaps and residual heightened risks associated with lower income to improve health equity in COVID-19 outcomes.

Background Hepatitis C virus (HCV) infection is associated with reduced quality of life and health utility. It is unclear whether this is primarily due to HCV infection itself or commonly co-occurring patient characteristics such as low income and mental health issues. This study aims to estimate and separate the effects of HCV infection on health utility from the effects of clinical and sociodemographic factors using real-world population-level data. Methods We conducted a cross-sectional retrospective cohort study to estimate health utilities in people with and without HCV infection in Ontario, Canada, from 2000 to 2014 using linked survey data from the Canadian Community Health Survey and health administrative data. Utilities were derived from the Health Utilities Index Mark 3 instrument. We used propensity score matching and multivariable linear regression to examine the impact of HCV infection on utility scores while adjusting for clinical and sociodemographic factors. Results There were 7,102 individuals with hepatitis C status and health utility data available (506 HCV-positive, 6,596 HCV-negative). Factors associated with marginalization were more prevalent in the HCV-positive cohort (e.g., household income <$20,000: 36% versus 15%). Propensity score matching resulted in 454 matched pairs of HCV-positive and HCV-negative individuals. HCV-positive individuals had substantially lower unadjusted utilities than HCV-negative individuals did (mean ± standard error: 0.662 ± 0.016 versus 0.734 ± 0.015). The regression model showed that HCV positivity (coefficient: −0.066), age, comorbidity, mental health history, and household income had large impacts on health utility. Conclusions HCV infection is associated with low health utility even after controlling for clinical and sociodemographic variables. Individuals with HCV infection may benefit from additional social services and supports alongside antiviral therapy to improve their quality of life. Highlights Hepatitis C virus (HCV) infection is associated with reduced quality of life and health utility. There is debate in the literature on whether this is primarily due to HCV infection itself or commonly co-occurring patient characteristics such as low income and mental health issues. We showed that individuals with HCV infection have substantially lower health utilities than uninfected individuals do even after controlling for clinical and sociodemographic variables, based on a large, real-world population-level dataset. Socioeconomically marginalized individuals with HCV infection had particularly low health utilities. In addition to improving access to HCV testing and treatment, it may be beneficial to provide social services such as mental health and financial supports to improve the quality of life and health utility of people living with HCV.

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

Background Since the Omicron variant emerged, uptake of booster doses of COVID-19 vaccines has gradually decreased both in the general population and among individuals at increased risk of severe COVID-19, such as patients with lung cancer. COVID-19 vaccine effectiveness (VE) has not been estimated in patients with lung cancer in the Omicron era. Methods In this test-negative design study using linked population-based cancer registry, health administrative, vaccination, and public health surveillance databases, we included all patients with active lung cancer or mesothelioma living in Ontario, Canada, who were tested for SARS-CoV-2 by RT-PCR from January 2, 2022, to August 31, 2023. We estimated VE against COVID-19-related severe outcomes (hospitalization or death) 7-179 days and ≥180 days following vaccination. Results During the study period, 13,622 patients with active lung cancer or mesothelioma underwent SARS-CoV-2 testing, with 1,371 (10.1%) positive. After exclusions, we analyzed 6,037 testing episodes, including 1,354 test-positive and 4,683 randomly selected test-negative episodes. Overall, COVID-19-associated hospitalization and mortality rates were 7.3% and 4.0%, respectively. Across both groups, 126/439 hospitalized patients (28.7%) and 116/5,598 non-hospitalized patients died (2.1%) (p=0.001). After multivariable adjustment, VE against severe COVID-19 was 56% (95%CI, 29%, 72%) 7-179 after vaccination and 10% (-45%, 44%) ≥180 days after vaccination. Conclusion Overall, COVID-19 VE against severe outcomes appears to be considerably lower for patients with active lung cancer or mesothelioma than the general population and decreases substantially beyond 180 days after vaccination. Our finding supports administration of COVID-19 booster doses in patients with lung cancer and mesothelioma every 6 months. Disclosures All Authors: No reported disclosures

Background While it is well established that HIV-positive and non-HIV immunocompromised patients are susceptible to Pneumocystis pneumonia (PCP), comparing PCP outcomes between patients with different underlying immunocompromising conditions is critically important to optimize chemoprophylaxis strategies. Methods In this population-based cohort, we determined contributing factors to 90-day all-cause mortality following PCP diagnosis among patients living with HIV (PLWH) and solid organ transplant recipients (SOTRs) hospitalized in Ontario, Canada between Apr/1/2002 and Dec/31/2022. We linked data from provincial health administrative databases using unique encoded identifiers and included all adult patients hospitalized with PCP based on diagnostic codes from hospital discharge abstracts. We used logistic regression models to estimate unadjusted and adjusted odds ratios (uOR and aOR) and 95% confidence intervals (95%CI) for the associations between underlying immunocompromising conditions and PCP outcomes. Results A total of 879 patients were hospitalized with PCP, including 121 SOTRs (13.7%) and 758 PLWH (86.2%). 90-day mortality rates were 19.8% in SOTRs and 13.2% in PLWH. In the unadjusted model, 90-day mortality was not significantly associated with organ transplantation (OR=1.58; 95%CI, 0.96-2.62) or HIV infection (OR=0.62; 95%CI, 0.38-1.03). Comparing HIV patients to liver SOTRs, liver SOTRs experienced higher mortality (uOR=8.54, 95%CI=3.11-23.46). In the adjusted model, liver transplantation was associated with an increased risk of 90-day mortality (aOR=4.36; 95%CI, 1.40-13.59). Among SOTRs, in the unadjusted analysis, liver transplant recipients had an increased risk of 90-day mortality (uOR=9.18; 95%CI, 3.00-28.09). Conclusion Among SOTRs, liver transplant recipients are at particularly higher risk of mortality following PCP diagnosis. Our findings may prompt a re-evaluation of current PCP prophylactic strategies in liver transplant patients. Disclosures All Authors: No reported disclosures

Objectives To evaluate among Ontario children and youth (<16 years old) with juvenile idiopathic arthritis (JIA) or inflammatory bowel disease (IBD), whether COVID-19 vaccines (Monovalent BNT162b2) were associated with adverse events of special interest (AESI) or health care utilization. Methods Using health administrative databases, all children/youth with JIA or IBD who received at least one vaccine were identified from November 2020 to December 2021 with follow-up until August 31, 2022. Self-controlled case series analyses were used to determine the relative incidence rates (RIR) of events in any 3-week period [AESI, Emergency Department (ED) visits, hospitalizations] and in any 1-month period [specialist visits] post-vaccine compared to control periods. Results We studied 1629 JIA and 1050 IBD patients. In the JIA cohort, the median age at vaccination was 12.0 years [Interquartile range (IQR): 10.0 to 14.0], and the median disease duration was 4.3 years (IQR: 2.0 to 7.5). By December 2021, 67.1% (n = 1093) received two doses and 24.1% (n = 393) received three doses. In the IBD cohort, the median age at vaccination was 13.0 (IQR: 11.0 to 14.0) with a median disease duration of 2.4 years (IQR: 1.1 to 4.8). Fifty-four percent (n = 565) received two doses and 36.3% (n = 381) received three doses. During risk periods, AESI was rarely reported. Relative to control periods, JIA and IBD patients demonstrated similar rates of hospitalizations [JIA: RIR: 0.76 (95% confidence interval [CI]: 0.25 to 2.33), IBD: RIR: 0.64 (95% CI: 0.29 to 1.41)], ED visits [JIA: RIR: 1.11 (95% CI: 0.77 to 1.59), IBD: RIR: 0.93 (95% CI: 0.61 to 1.43)], and specialist visits [JIA: RIR: 1.06 (95% CI: 0.89 to 1.26), IBD: RIR: 0.56 (95% CI: 0.22 to 1.43)]. Conclusions Overall, this study demonstrates the safety of the BNT162b2 vaccine in children/youths with JIA and IBD, with no associated increase in AESI or health care use.

Background: In May 2022, an outbreak of mpox emerged in Canada. In June 2022, the province of Ontario began offering first doses of a 2 dose regimen of Modified Vaccinia Ankara Bavaria Nordic (MVA BN) to those at high risk of exposure. Second doses became available in September 2022. To help increase dose 2 access and uptake, we sought to understand how individuals who received 2 doses differed from those who received only 1 dose. Methods: We linked provincial health administrative data of individuals who received >=1 dose of MVA-BN between June 6, 2022 and October 31, 2023 in Ontario. We used age-adjusted Poisson regression to examine the association between demographic, social, and economic characteristics; co-morbidities; and proxies for sexual exposure (e.g., bacterial sexually transmitted infection [STI] diagnoses) and proxies for healthcare engagement (e.g., syphilis testing, past receipt of other vaccines) with MVA BN dose 2 receipt. Results: Among 33,012 individuals with >=1 MVA BN dose, 38.2% (12,620) received 2 doses. Receipt of dose 2 versus only dose 1 was associated with region (e.g., Ottawa versus Toronto [prevalence ratio, PR=1.08, 95% confidence interval, CI 1.06-1.09]); syphilis testing (>=4 tests PR=1.12, 95%CI 1.11-1.14) or receiving a COVID-19, influenza, or other vaccine (PR=1.12, 95%CI 1.11-1.14) in the year before dose 1; and syphilis testing (>=4 tests PR=1.19, 95%CI 1.18-1.20) or bacterial STI diagnoses >3 months after dose 1 (>=4 diagnoses PR=1.07, 95% CI 1.05-1.08). Refugees were less likely to get dose 2 versus Canadian-born individuals or long term immigrants (PR=0.93, 95%CI 0.91-0.95). Conclusions: Our findings suggest lower healthcare access and/or engagement may play a role in limiting dose 2 receipt in Ontario. Public messaging around availability and eligibility of second doses, tailored strategies for eligible refugees, increased access outside healthcare venues, and adopting promotion strategies from regions with high uptake, may help increase dose 2 coverage.