This is a summary, written by members of the CITF Secretariat, of:

Richard L, Nisenbaum R, Brown M, Liu M, Pedersen C, Jenkinson JIR, Mishra S, Baral S, Colwill K, Gingras AC, McGeer A, Hwang SW. Incidence of SARS-CoV-2 Infection Among People Experiencing Homelessness in Toronto, Canada. JAMA Network Open. 13 March 2023;6(3):e232774; doi: 10.1001/jamanetworkopen.2023.2774

The results and/or conclusions contained in the research do not necessarily reflect the views of all CITF members.

A CITF-funded study, published in JAMA Network Open, found that people experiencing homelessness had high rates of SARS-CoV-2 infection throughout 2021 and 2022, particularly after the Omicron variant became dominant. Additional factors that were significantly associated with increased incidence of infection included alcohol consumption and recent immigration to Canada. This study was led by Dr. Stephen Hwang (Unity Health Toronto and University of Toronto) in collaboration with Dr. Allison McGeer (Mount Sinai Hospital) and Dr. Anne-Claude Gingras (Lunenfeld-Tanenbaum Research Institute).

Key findings:

  • Approximately 30% of the analysis population without history of infection at baseline had been infected by the six-month follow-up. More than 80% of infections occurred after the Omicron variant became dominant.
  • By spring 2022, almost half of the original cohort showed evidence of at least one SARS-CoV-2 infection.
  • Characteristics that were shown to be significantly associated with infection included:
    1. Response period, as those interviewed after the onset of the Omicron variant spread were six times more likely to have become infected.
    2. Immigration status, with recent immigrants more likely to become infected than Canadian-born individuals.
    3. Alcohol consumption, with those reporting recent consumption having higher rates of infection than those who did not.
  • Self-reported housing characteristics were not significantly associated with incident infection.

This study of an underserved and vulnerable population provides data that highlight factors that can be prioritised for future public health policy. Study limitations include not being fully representative of the population experiencing homelessness in Toronto, self-reported housing data that can be subject to bias, and possibly underestimating infections. The latter is because the researchers used only a single antibody measurement to determine evidence of infection in vaccinated individuals.

From June to September 2021, the researchers recruited 736 participants by random number schedule from among various shelters and encampments across Toronto. From these, 415 individuals without history of infection at baseline and with follow-up data were included in the main analysis. Participants provided sociodemographic information, housing history, and were negative for current or prior SARS-CoV-2 infection at baseline. Follow-ups were conducted at three months and six months after recruitment.