Measuring HPV vaccination coverage in Australia: comparing two alternative population-based denominators

Area of Science:

• Public Health
• Vaccinology
• Health Services Research

Background:

• Accurate population denominators are crucial for monitoring vaccination program effectiveness.
• The National HPV Vaccination Program Register (NHVPR) in Australia requires reliable population data for coverage calculations.
• Previous studies have not extensively compared different population denominators for HPV vaccine coverage across diverse geographical areas.

Purpose of the Study:

• To compare the utility of two distinct population-based denominators: the Australian Bureau of Statistics Estimated Resident Population (ABS ERP) and Medicare enrolments.
• To evaluate HPV vaccine coverage calculations across different age groups, Australian states/territories, and remoteness classifications.
• To inform the selection of an optimal denominator for ongoing HPV vaccination program monitoring.

Main Methods:

• Analysis of data from the National HPV Vaccination Program Register (NHVPR) at Local Government Area (LGA) level.
• Stratification of data by state/territory and the Australian Standard Geographical Classification Remoteness Structure.
• Calculation of HPV vaccine coverage proportions using both ABS ERP and Medicare enrolments as the denominator.

Main Results:

• National HPV vaccine coverage estimates were marginally higher using Medicare enrolments compared to ABS ERP for both 12–17-year-old females (70.8% vs. 70.4%) and 18–26-year-old females (33.3% vs. 31.9%).
• The most significant discrepancies in coverage estimates were observed in Australia's remote geographical areas.
• Interpretation of coverage differences in Remote and Very Remote areas was complicated by small resident populations.

Conclusions:

• There is negligible variation in HPV vaccine coverage estimates between Medicare enrolments and ABS ERP denominators nationally.
• Coverage estimates in Remote and Very Remote areas present interpretation challenges due to population size, impacting denominator comparisons.
• Adopting Medicare enrolments as the denominator for the ongoing national HPV vaccination program is unlikely to substantially alter routine coverage estimates.