Effectiveness of HPV vaccination against high grade cervical lesions in Japan.

The effectiveness of HPV vaccine against HSIL+ (pathologically diagnosed CIN2+) in the first cohort in Japan was investigated in 22,743 women aged 20 to 29 years (parts of national cervical cancer screening program of FY [fiscal year] 2015, the Japan Cancer Society). Vaccinated women had a statistically significant 69% lower risk of HSIL+ as compared to the unvaccinated women; the crude relative risk estimate was 0.31 (95% CI: 0.11-0.83; p-value = 0.013) by normal approximation and 0.31 (95% CI: 0.08-0.80; p-value = 0.009) by the exact Poisson regression. The effect of age was not significant (chisq = 7.7 (df = 9), p-value = 0.569) and the estimate of relative risk remained essentially intact after adjustment for age. This study brings scientific evidence on the effectiveness of HPV vaccine on development of cervical high grade lesions.