Patients
Among 1534 patients who participated in this study from April 2021 to November 2022, 1529 eligible women aged 16 to 39 years (mean age, 30.4 ± 5.5 years) underwent evaluation. The patients visited 11 outpatient clinics (9 private clinics and 2 hospitals) in 7 districts in Japan (Hokkaido, Tokyo, Kanagawa, Aichi, Ishikawa, Osaka, and Okinawa) for various reasons. All patients provided written informed consent prior to participation in this study. All medical facilities received approval to participate from their respective independent ethics committees/institutional review boards. This study was conducted in accordance with the ethical guidelines for epidemiological research and the ethical principles of the Declaration of Helsinki.
The present study was performed using the same approach implemented in the J-HERS performed from October 2010 to March 2012 (21) (Fig. 1). Therefore, the present study was designated “J-HERS 2021” and the previous study was designated “J-HERS 2011.” The J-HERS 2011 study was conducted concurrently with the Japanese national and local governments’ special HPV vaccination program, as depicted in Figure 1. Consequently, a limited number of participants underwent vaccination during that study. The interval between the periods included in these two studies varied from 9 years 1 month to 12 years 1 month.
Analysis of HPV vaccination rates among J-HERS 2021 participants revealed that the rate was highest among women aged 22 to 27 years. Therefore, the following age groups were established in the present study: 16 to 21, 22 to 27, 28 to 33, and 34 to 39 years. Women were excluded if they had past or present malignant diseases, lacked a uterus, or had no history of sexual intercourse. The reasons for the patients’ visits were as follows: cervical cancer screening; follow-up for abnormal Pap test results, including diagnosis of CIN1/2; and obstetrics or gynecology consultations including pregnancy diagnosis, menstrual disorders, sexually transmitted infections, endometriosis, adenomyoma, uterine leiomyoma, and benign ovarian cysts (Table 1).
We evaluated the age-adjusted data of the 5062 patients who participated in the previous J-HERS 2011 study for comparison with the patient population in the present study. We intended to assess the prevalences of cervical lesions and HPV infection, thus enabling examination of HPV vaccination effectiveness in the context of the nationwide HPV vaccine program in Japan, 9 to 12 years after initial implementation. The age distribution did not differ between the two studies; however, the rates of visiting for CIN follow-up and obstetrics or gynecology consultations were significantly higher in J-HERS 2011 than in J-HERS 2021. To avoid bias related to the different backgrounds between the two studies, only patients who visited for cervical cancer screening were included in the analysis (J-HERS 2021, n = 1130; J-HERS 2011, n = 3236).