Immunising women aged 20 years or older against HPV infection is too late to offer adequate protection against genital warts, say researchers.
The study
Researchers in Sweden followed 2,209,263 females aged 10 to 44 years and collected information on HPV vaccinations from vaccination registers. Vaccine effectiveness was calculated using incident rate ratios of genital warts, which used a time to first event of genital warts as part of the analysis.
The findings
Vaccine effectiveness was highest in girls vaccinated before the age of 14, with an effectiveness of 93%. This dropped to 80% for girls vaccinated aged 14 to 16 years, 71% for girls vaccinated at 17 to 19 years and 48% for women vaccinated aged 20 to 22 years.
What does it mean for GPs?
The authors concluded that among women vaccinated at 20 years or older ‘there was low to immeasurable effectiveness and suggestive evidence that vaccinations tended to reach women at high genital warts risk.’ They added that it suggested ‘that vaccinations in this age group were not adequate for achieving the intended health benefit.’
Journal of the National Cancer Institute, online 13 March
