The prevalence of tuberculosis infection among foreign-born Canadians: a modelling study

Background:

The prevalence of tuberculosis infection is critical to the design of tuberculosis prevention strategies, yet is unknown in Canada. We estimated the prevalence of tuberculosis infection among Canadian residents born abroad.

Methods:

We estimated the prevalence of tuberculosis infection by age and year of migration to Canada for people from each of 168 countries by constructing country-specific and calendar year-specific trends for annual risk of infection using a previously developed model. We combined country-specific prevalence estimates with Canadian Census data from 2001, 2006, 2011, 2016 and 2021 to estimate the overall prevalence of tuberculosis infection among foreign-born Canadian residents.

Results:

The estimated overall prevalence of tuberculosis infection among foreign-born people in Canada was 25% (95% uncertainty interval [UI] 20%- 35%) for census year 2001, 24% (95% UI 20%-33%) for 2006, 23% (95% UI 19%- 30%) for 2011, 22% (95% UI 19%-28%) for 2016 and 22% (95% UI 19%-27%) for 2021. The prevalence increased with age at migration and incidence of tuberculosis in the country of origin. In 2021, the estimated prevalence of infection among foreign-born residents was lowest in Quebec (19%, 95% UI 16%- 24%) and highest in Alberta (24%, 95% UI 21%-28%) and British Columbia (24%, 95% UI 20%-30%). Among all foreign- born Canadian residents with tuberculosis infection in 2021, we estimated that only 1 in 488 (95% UI 185- 1039) had become infected within the 2 preceding years.

Interpretation:

About 1 in 4 foreign-born Canadian residents has tuberculosis infection, but very few were infected within the 2 preceding years (the highest risk period for progression to tuberculosis disease). These data may inform future tuberculosis infection screening policies.