Cervical cancer has been increasing rapidly in Japanese young women, however, administration of the human papillomavirus (HPV) vaccine decreased dramatically in Japan after extensive news of adverse vaccine events and suspension of the governmental recommendation for the vaccine. Our aim of this study is to clarify the effectiveness of HPV vaccination against HPV infection and cervical cancer in Japanese women.
Six hundreds eighty one Japanese women aged 20-21 years were enrolled in this study between April 2014 and January 2016 in Niigata, Japan. We obtained information of sexual behavior and HPV vaccination in 584 girls (85.7% of all registrants). We investigated Pap smear and HPV infection screening(QIAGEN HCⅡ) in all registrants, then if HPV was positive, we added HPV typing(MEBGEN TM HPV kit). A Fisher’s exact test and chi-square test was used in this statistical analysis.
There were 247 cases (42.3%) in HPV vaccine-exposed (vaccine+) group and 337 cases (57.7%) in HPV vaccine-unexposed (vaccine-) group. The HPV infection rate was significantly higher as sexual debut age was younger and number of sexual partners increased, respectively (p<0.0001). However, the HPV vaccination rate tended to decrease as sexual behavior became active. No one had HPV 16 and 18 infection in vaccine+ group, on the other hand, 6 women (6/337=1.7%) had HPV 16 and 18 infection in vaccine- group. This difference was statistically significant (p=0.042). The HPV infection rate of vaccine+ group was not significantly lower than that of vaccine- group in early sexual debut age women (<15 years old).
Our survey showed the efficacy of HPV vaccine against HPV 16 and 18 infection in Japanese women. The efficacy appear to be different according to the sexual debut age.