Social inequalities in COVID-19 death by area-level income in 11.2 million people in Ontario, Canada: patterns over time and the mediating role of vaccination

Linwei Wang; Sarah Swayze; Korryn Bodner; Andrew Calzavara; Sean P Harrigan; Arjumand Siddiqi; Stefan D Baral; Peter C Austin; Janet Smylie; Maria Koh; Hind Sbihi; Beate Sander; Jeffrey C Kwong; Sharmistha Mishra

doi:10.1093/aje/kwaf051

Social inequalities in COVID-19 death by area-level income in 11.2 million people in Ontario, Canada: patterns over time and the mediating role of vaccination

Am J Epidemiol. 2025 Mar 7:kwaf051. doi: 10.1093/aje/kwaf051. Online ahead of print.

Authors

Linwei Wang¹, Sarah Swayze², Korryn Bodner¹, Andrew Calzavara², Sean P Harrigan³, Arjumand Siddiqi^{4

5

6

7}, Stefan D Baral⁸, Peter C Austin^{2

9

10}, Janet Smylie^{4

11}, Maria Koh², Hind Sbihi^{3

12}, Beate Sander^{2

9

13

14}, Jeffrey C Kwong^{2

4

14

15

16}, Sharmistha Mishra^{1

2

4

9

17

18}

Affiliations

¹ MAP-Centre for Urban Health Solutions, St. Michael's Hospital, Unity Health Toronto, Toronto, ON, Canada.
² ICES, Toronto, ON, Canada.
³ BC Centre for Disease Control, UBC BCCDC, Vancouver, BC, Canada.
⁴ Dalla Lana School of Public Health, University of Toronto, Toronto, ON, Canada.
⁵ Hospital for Sick Children, Toronto, ON, Canada.
⁶ Department of Social and Behavioural Sciences, Harvard School of Public Health, MA, US.
⁷ Gillings School of Global Public Health, University of North Carolina - Chapel Hill, NC, US.
⁸ Department of Epidemiology, Johns Hopkins School of Public Health, Baltimore, MD, US.
⁹ Institute of Health Policy, Management, and Evaluation, University of Toronto, Toronto, ON, Canada.
¹⁰ Sunnybrook Health Sciences Centre, Toronto, ON, Canada.
¹¹ Well Living House, Li Ka Shing Knowledge Institute, Unity Health Toronto, Toronto, ON, Canada.
¹² University of British Columbia, School of Population and Public Health, Vancouver, BC, Canada.
¹³ Toronto Health Economics and Technology Assessment (THETA) Collaborative, University Health Network, Toronto, Canada.
¹⁴ Public Health Ontario, Toronto, ON, Canada.
¹⁵ Department of Family and Community Medicine, University of Toronto, Toronto, ON, Canada.
¹⁶ University Health Network, Toronto, ON, Canada.
¹⁷ Institute of Medical Sciences, University of Toronto, Toronto, ON, Canada.
¹⁸ Department of Medicine, University of Toronto, Toronto, ON, Canada.

PMID: 40069958
DOI: 10.1093/aje/kwaf051

Abstract

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.

Keywords: COVID-19; Causal mediation analysis; Health equity; Income; Social inequality; Vaccination.