COVID-19 immunisation among individuals with opioid use disorder in Ontario: a population-based cohort study

Background — The COVID-19 pandemic exacerbated health inequities, particularly among individuals with opioid use disorder (OUD). Disparities in vaccine uptake among people with OUD remain poorly understood. This study assessed COVID-19 immunisation rates among individuals with OUD compared with the general population in Ontario, Canada.

Methods — This population-based retrospective cohort study used linked administrative health data to compare COVID-19 vaccination rates between individuals diagnosed with OUD and a 10% random sample of individuals without OUD. Ontario residents aged >15 years with continuous healthcare coverage as of the censor date, 16 March 2020, were included. Inverse Probability of Treatment Weighting (IPTW) was applied to balance confounders, and Cox proportional hazards models estimated adjusted HRs (aHRs) for receiving two and three or more vaccine doses.

Results — The cohort included 105 733 individuals with OUD and 1 185 993 without OUD. Individuals with OUD had a lower hazard of receiving two vaccine doses (aHR: 0.75, 95% CI 0.73 to 0.76) and three or more doses (aHR: 0.69, 95% CI 0.67 to 0.70). The rate of two-dose and three-dose vaccination was also lower among those with OUD (115.3 vs 149.0 per 100 000 person-years and 44.7 vs 77.5 per 100 000 person-years).

Conclusion — Individuals with OUD had lower COVID-19 vaccination rates, suggesting barriers to access and uptake. Addressing these disparities through targeted interventions is crucial for equitable public health responses.