SARS-CoV-2 infection among physicians over time in Ontario, Canada: a population-based retrospective cohort study

Abstract

Aim: To assess this risk of SARS-CoV-2 infection among Ontario physicians by specialty and in comparison with non-physician controls during the COVID-19 pandemic.

Methods: In this retrospective cohort study, the primary outcome was incident SARS-CoV-2 infection confirmed by polymerase chain reaction (PCR). Secondary outcomes were hospitalization, use of critical care, and mortality.

Results: From March 1, 2020 to December 31, 2022, 6172/30 617 (20%) active Ontario physicians tested positive for SARS-CoV-2. Infection was less likely if physicians were older (OR 0.78 [0.76-0.81] per 10 years), rural residents (OR 0.70 [0.59-0.83]), and lived in more marginalized neighborhoods (OR 0.74 [0.62-0.89]), but more likely if they were female (OR 1.14 [1.07-1.22]), worked in long-term care settings (OR 1.16 [1.02-1.32]), had higher patient volumes (OR 2.05 [1.82-2.30] for highest vs lowest), and were pediatricians (OR 1.25 [1.09-1.44]). Compared with community-matched controls (n=29 763), physicians had a higher risk of infection during the first two waves of the pandemic (OR 1.38 [1.20-1.59]) but by wave 3 the risk was no longer significantly different (OR 0.93 [0.83-1.05]). Physicians were less likely to be hospitalized within 14 days of their first positive PCR test than non-physicians (P<0.0001), but there was no difference in the use of critical care (P=0.48) or mortality (P=0.15).

Conclusion: Physicians had higher rates of infection than community-matched controls during the first two waves of the pandemic in Ontario, but not from wave 3 onward. Physicians practicing in long-term care facilities and pediatricians were more likely to test positive for SARS-CoV-2 than other physicians.

Figure 1

Physician cohort creation. Data sources and strategy to identify physicians from health administrative databases. RPDB – Registered Persons Database; CPDB – Corporate Provider Database; HIN – health insurance number (unique person identifier); CPSO - College of Physicians and Surgeons of Ontario. When the first and last name were reversed, for example, this means the first name from RPDB was matched to the last name from CPDB and the last name from RPDB was matched to the first name from CPDB.

Figure 2

Time until SARS-CoV-2 infection among physicians by sex and location. Cumulative incidence plot showing the time until the first SARS-CoV-2 infection since the start of the COVID-19 pandemic in Ontario stratified by physician sex (A) and employment at a long-term care (LTC) facility or equivalent (B).

Figure 3

Variation in SARS-CoV-2 infection by specialty. (A) Funnel plot for the percent of physicians by specialty testing positive for SARS-CoV-2 on polymerase chain reaction (PCR) as a function of the number of physicians per specialty. (B) Cumulative incidence plot showing the time until the first SARS-CoV-2 infection since the start of the COVID-19 pandemic in Ontario stratified by select physician specialties. (C) Association between SARS-CoV-2 testing rate and positivity by specialty. Solid line is the regression line for this association (physicians only). FP/GP – family practice/general practice. Testing rate was restricted to physicians who did not test positive to avoid testing bias following a positive test, which would artificially strengthen this observed correlation.

Figure 4

Outcome by cohort. (A) Cumulative incidence plot showing the time until the first SARS-CoV-2 infection since the start of the COVID-19 pandemic in Ontario stratified by cohort (n = 29 763 per group); (B) Kaplan-Meier plot for all-cause mortality since the first SARS-CoV-2 infection, by cohort.