Timeliness and completeness of routine childhood vaccinations in children by two years of age in Alberta, Canada.

Objectives: Assessing timeliness and completeness of vaccine administration is important for evaluating the effectiveness of immunization programs. Few studies have reported timeliness, particularly in Canada. The objective of this study was to examine timeliness of the receipt of vaccination for each routine childhood recommended vaccine by 24 months of age among children in a community-based pregnancy cohort in Calgary, Alberta.
Methods: Survey data from a community-based pregnancy cohort in Alberta were linked to Public Health vaccination records of children (n = 2763). The proportion of children receiving early, timely, delayed, or no vaccination was calculated. A dose was considered early if it was administered before the recommended age in days as per the vaccination schedule, timely if administered at any time from start of recommended age in days to age in days when delay counts were initiated, and delayed if it was administered on or after age in days when delay counts were initiated. Series completion rates were also calculated.
Results: For multi-dose vaccines, over 80% of children had timely doses at 2, 4 and 6 months. By 12 months, this proportion decreased to 65% (95% CI: 63%-66%) for meningococcal conjugate group C, 61% (95% CI: 59%-62%) for measles antigen-containing vaccines and 64% (95% CI: 62%-65%) for varicella antigen-containing vaccines. At 18 months, only 55% (95% CI: 53%-56%) of the children had a timely 4th dose of diphtheria, acellular pertussis, tetanus, polio, and Haemophilus influenzae type b vaccine. Eventual series completion rate for all recommended vaccines was 77% (95% CI: 75%-79%).
Conclusion: The timeliness and completeness of routine childhood vaccination in preschool children in this community-based pregnancy cohort is lower than provincial targets. Data on timeliness of vaccination can inform further work on barriers and enablers to vaccination in order to meet provincial targets.