Lower Incidence of Cervical Intraepithelial Neoplasia among Young Women with Human Papillomavirus Vaccination in Miyagi, Japan

Nobuyoshi Ozawa, Kiyoshi Ito, Toru Tase, Daisuke Shibuya, Hirohito Metoki, Nobuo Yaegashi

The Japanese national immunization programme for Human Papillomavirus (HPV) started in 2010. Vaccination rates increased up to 70% in women in the 1996-1999 birth. However, the proactive recommendation for HPV vaccine was suspended in 2013, following repeated media reports of adverse events. Vaccination rates plumped to less than 1% in women born since 2002. In this study, incidence of abnormal cytology and histology was examined in terms of HPV vaccination among 5,924 women aged 20 to 24 years in the fiscal year (FY) 2014 and 2015. The total rate of vaccination was 16.9% (1,002/5,924). In case of FY 2015, the rates of vaccination were 59.26%, 49.68%, 11.97%, 9.08%, and 4.58% in those aged 20, 21, 22, 23, and 24 years old, respectively. The rates of high-grade squamous intraepithelial lesion (HSIL) or worse were 0.20% (2/1,002) in women with HPV vaccination and 1.14% (56/4,922) in those without HPV vaccination, indicating a significant reduction of 82.46% with vaccination (P < 0.0001). The rates of cervical intraepithelial neoplasia (CIN) 1+ were 0.80% (8/1,002) in women with vaccination and 2.28% (112/4,922) in those without vaccination. The reduction rate of CIN1+ was 64.91% (P = 0.0025). The rates of CIN2+ were 0.10% (1/1,002) with vaccination and 0.69% (34/4,922) without vaccination. The reduction rate of CIN2+ was 85.51% (P = 0.0261). Our data are the first to demonstrate a significant reduction of CIN2+ cases in an Asian population. Scientific discussion is needed to restart the proactive recommendation for HPV vaccine in Japan.