Impact of a population-based HPV vaccination program on cervical abnormalities: a data linkage study

Area of Science:

• Public Health
• Vaccinology
• Gynecologic Oncology

Background:

• Australia initiated a publicly funded national human papillomavirus (HPV) vaccination program in April 2007.
• The program utilized the quadrivalent HPV vaccine, targeting adolescent girls and offering catch-up programs for older females.

Purpose of the Study:

• To evaluate the population-level vaccine effectiveness of the school-based HPV vaccination program.
• To assess the impact of the HPV vaccine on cervical abnormalities in Victoria, Australia.

Main Methods:

• Linked data from the Victorian Cervical Cytology Registry and the National HPV Vaccination Program Register.
• Created a cohort of vaccinated and unvaccinated women eligible for the HPV program.
• Calculated vaccine effectiveness (VE) and hazard ratios (HR) for cervical abnormalities using proportional hazards regression.

Main Results:

• Significantly lower detection rates of high-grade cervical abnormalities (HG) and high-grade cytology (HGC) in vaccinated women compared to unvaccinated women.
• Vaccine effectiveness for CIN3+/AIS was 47.5% for completely vaccinated women and 36.4% for women receiving any dose.
• Effectiveness was greatest in the youngest women and negatively associated with age; one or two doses showed no significant HR difference from 1.0.

Conclusions:

• The population-based school HPV vaccination program substantially reduced cervical abnormalities within five years.
• The youngest women in the program experienced the greatest vaccine effectiveness.
• The findings support the ongoing implementation and importance of school-based HPV vaccination programs.