Methods used for immunization coverage assessment in Canada, a Canadian Immunization Research Network (CIRN) study

Area of Science:

• Public Health
• Epidemiology
• Immunization Informatics

Background:

• Accurate immunization data is crucial for evaluating vaccine coverage, safety, and effectiveness.
• Current methods and data sources for assessing vaccine coverage across Canada are not systematically described.
• Variations in data collection and analysis can lead to inconsistencies in reported vaccine coverage rates.

Purpose of the Study:

• To systematically examine and describe the methods used to determine immunization coverage in Canada.
• To compare routine infant and childhood immunization coverage estimates between a national survey and provincial/territorial data.
• To identify differences in methodologies and their impact on coverage estimates.

Main Methods:

• Information on provincial, territorial, and federal methods for assessing immunization coverage was collected from key informants.
• Provincial and territorial coverage estimates for select antigens and birth cohorts were gathered.
• Data from the Canadian 2013 Childhood National Immunization Coverage Survey (cNICS) was used for comparison.

Main Results:

• Significant differences in methodologies for measuring immunization coverage were observed across Canadian provinces and territories (P/Ts).
• Most P/Ts assess up-to-date (UTD) coverage, with some also assessing on-time coverage.
• The concordance between P/T and cNICS coverage estimates varied by jurisdiction, antigen, and age group, indicating data inconsistencies.

Conclusions:

• There are considerable differences in data sources, processes, and calculation methods for immunization coverage assessment among Canadian P/Ts.
• These methodological variations raise questions about the true proportion of fully vaccinated children in Canada.
• Standardization of immunization data assessment methods is needed for reliable national vaccine coverage evaluation.