Immunization status of children at kindergarten entry in Alberta, Canada.

Objectives: Little is known about immunization coverage among kindergarten-aged children in jurisdictions that do not require children's immunization records to be provided at school entry. Thus, we assessed immunization coverage and associated characteristics of a 2008 birth cohort of Alberta children at kindergarten entry as compared with at the end of grade one.

Methods: This retrospective cohort study used population-based administrative health data for childhood vaccines in Alberta, Canada. We categorized and compared immunization status of children as follows: (a) complete at kindergarten entry; (b) incomplete at kindergarten entry but complete at the end of grade one; and (c) still incomplete at the end of grade one. To assess factors associated with immunization status, we used multinomial logistic regression.

Results: Immunization coverage for the complete vaccine series for children (N = 41,515) at kindergarten entry was suboptimal (44.5%, 95% CI 44.0-45.0) and substantially lower than for children at the end of grade one (74.8%, 95% CI 74.3-75.2). Young maternal age, not living with a partner, and having > 1 child in a household were associated with incomplete immunization status at kindergarten entry. Midwife-assisted hospital and home delivery was strongly associated with incomplete immunization status at the end of grade one.

Conclusion: Immunization coverage at kindergarten entry was strikingly low. Risk factors for incomplete immunization status were identified that require particular attention when addressing immunization coverage. The school-based catch-up immunization program in grade one seems to have substantially improved coverage among children, suggesting a potential benefit of shifting the catch-up program from grade one to kindergarten entry.