Vaccine-preventable disease-related hospitalization among immigrants and refugees to Canada: Study of linked population-based databases

While immigrants tend to be healthier especially when they first arrived, this healthy immigrant effect may not apply to vaccine-preventable diseases (VPD) especially among immigrants from countries without vaccination programs. There is therefore an important information gap regarding differential health outcome and hospitalization usage by immigrant status, landing cohort, world region and immigrant category. This study focused on acute-care hospitalization, and used two recently linked population-based databases in Canada, namely, the 2006 Census linked to the Hospital Discharge (DAD), and the Immigrant Landing File linked to the DAD (ILF-DAD) to estimate crude and age-standardized VPD-related hospitalization rates (ASHR) by the above-mentioned immigrant characteristics to be compared with that for overall Canadian-born reference population. Based on the 2006 Census-DAD linked database, VPD-specific ASHR for overall immigrants was significantly higher than that for the Canadian-born population (1.6, 95% CI, 1.5, 1.6 vs 1.2, 95% CI, 1.1, 1.2, respectively). VPD-specific ASHRs by landing cohorts also increased with years in Canada (e.g. 1.4, 95% CI, 1.3, 1.5 for the 1990-2006 cohort, and 1.6, 95% CI, 1.5, 1.7 for the pre-1980 cohort). Based on the 1980-2006 ILF-DAD, the VPD-specific ASHRs were highest among Southeast and East Asians (e.g. 2.1, 95% CI, 1.9, 2.3 for East Asia). Compared with the Canadian-born, economic class immigrants overall had significantly lower ASHR (1.4, 95% CI 1.2, 1.6), but the low rate was mainly due to the dependants (spouse or children) within this class (0.8, 95% CI 0.6, 1.1). Both family and refugee categories had significantly higher ASHRs (1.3, 95% CI, 1.2, 1.5 and 1.7, 95% CI, 1.4, 2.1, respectively), especially among those refugees assisted by government (2.0, 95% CI, 1.4, 2.6). With increasing immigration, changing source countries and emerging needs for refugee settlements in Canada, these newly linked datasets help to monitor VPD-related hospitalization pattern among Canadian immigrants.