Objective
Human papillomavirus (HPV) vaccine was licensed in Japan in 2009. It was funded by a budget from both the national and local governments from 2011. The HPV vaccine program targets 12-16-year-old girls. The aim of this study was to evaluate the effectiveness of the vaccine by comparing trends in incidence rates of cytological abnormalities from cervical screening data in Saitama city, Japan.
Methods
Omiya Medical Association in Saitama city performs cervical cancer screening using cytology and ASC-US triage with HPV testing. Participants attending the screening program between April 2015 and January 2016 were enrolled in this study. At screening, women had to fill in a questionnaire about HPV vaccine status. Incidence of cytological abnormalities was compared between the group and unvaccinated group. ASC-US or worse was defined as a cytological abnormality.
RESULTS
Out of all of 11,703 participants, 201 women (1.7%) were vaccinated and 11,502 women were unvaccinated. Overall cervical screening results showed that 5 cases (2.5%) with cytological abnormalities were in vaccinated women and 263 cases (2.3%) in unvaccinated women. In women aged 20-25yrs (birth years 1995-1990), coverage of HPV vaccine was 68.0%, 59.4%, 3.8%, 5.7%, 4.8% and 3.9%, respectively. The first and second vaccinated birth cohorts had relatively high coverage. Furthermore, the results of cervical screening from a group of 485 women of 20 to 25 years showed 2 cases (2.7%) in vaccinated women and 21 cases (5.1%) in unvaccinated women, respectively. Incidence risk ratio was 0.524 [95%CI：0.120−2.286].
Conclusion
Incidence of cervical abnormalities seems to be decreasing in the cohort of young women with higher vaccine coverage, but as of 2015, it is not yet statistically significant. Further surveillance is necessary to evaluate the effectiveness of the HPV vaccine in Japan.