Abstract
In 2008, a quadrivalent human papillomavirus (HPV) vaccine (genotypes 6, 11, 16, 18) became available in New Zealand. This study investigated whether the proportion of cervical intraepithelial neoplasia grade 2 (CIN2) lesions associated with HPV genotypes 16 and 18 changed over time in young women recruited to a prospective CIN2 observational management trial (PRINCess) between 2013 and 2016. Partial HPV genotyping (16, 18, or other high risk HPV) was undertaken on n = 392 women under 25 years (mean age 21.8, range 17-24) with biopsy-diagnosed CIN2. High risk HPV genotypes were detected in 96% of women with CIN2 lesions. Between 2013 and 2016, the proportion of women whose liquid-based cytology samples were HPV 16 or 18 positive decreased from 43% to 13%. HPV vaccination status was known for 78% of women. Between 2013 and 2016, the proportion of HPV 16/18 positivity did not significantly change in HPV-vaccinated women, but decreased from 66% to 17% in unvaccinated women. The reducing proportion of HPV 16/18-related CIN2 in our cohort of young New Zealand women may be attributable to the introduction of a national HPV vaccination program. The substantial decrease in HPV 16/18 positivity observed in unvaccinated women is likely to be due to a herd effect.