Beneficial Effects of Human Papillomavirus Vaccine for Prevention of Cervical Abnormalities in Miyagi, Japan

HPV Vaccine Issues in Japan: A review of our attempts to promote the HPV vaccine and to provide effective evaluation of the problem through social-medical and behavioral-economic perspectives

In Japan, subsidies from local and national government programs for HPV vaccination of girls aged 13-16 began in 2010. By 2013, HPV vaccines were being used routinely for vaccinating girls aged 12-16 as part of its national immunization program. However, in June of 2013, in response to reports of possible adverse reactions to the vaccine, Japan's Ministry of Health, Labor, and Welfare (MHLW) announced a 'temporary suspension' of its governmental recommendation for HPV vaccination. The vaccination rate quickly dropped from 70 % of age-eligible girls to almost zero. It was not until 2021 that the government's recommendation suspension finally ended. The efficacy and safety of the HPV vaccine is now well documented, yet Japan has failed to reestablish any credible level of HPV vaccination. The World Health Organization (WHO) warned that Japan's HPV vaccination debacle was likely to result in real harm to the girls who lacked its protection; something we have already demonstrated with real-world data. To reinvigorate the HPV vaccination program in Japan to its prior levels, in the face of the current high level of HPV vaccine hesitancy, we will have to address the irrationality of human decision-making pointed out by behavioral economics. The Japanese government must act expeditiously to promote stronger cervical cancer control measures.

Estimation of self-funded human papillomavirus vaccine recipients from Japan's previously assumed "unvaccinated generation"

Precise vaccination data is essential to accurately estimate the effectiveness of the human papillomavirus (HPV) vaccine against HPV-related cancers. In Japan, the number of subsidized HPV vaccinations can be tracked through registries, but the number of self-funded vaccinations has not been tracked. The number of individuals who chose to receive the vaccine at their own expense, despite being ineligible for public subsidies due to their age, is unknown and has been nominally considered to be zero. Our aim is to produce a more accurate estimate of this number using recently released proprietary data. First, we estimated the total number of self-funded HPV vaccinations occurring from 2010 to 2012 using public data from the Ministry of Health, Labour and Welfare and our previously reported data on the number of HPV vaccinations eligible for public subsidy. Second, using proprietary data from the vaccine manufacturer, we calculated the distribution of self-funded vaccination shots by age. Finally, we combined these data to estimate the number of self-funded HPV vaccinations by birth fiscal year (FY) relative to a yearly reference population. We found that 78,264 individuals born in FY1993 and 58,190 born in FY1992 self-funded their vaccinations, representing 13.6% and 10.0% of the reference population, respectively. Additionally, we found that 5%-10% of individuals born from FY1986 to FY1991 self-funded their vaccinations. Our study revealed for the first time that a certain number of individuals from the "HPV unvaccinated generation," ineligible for subsidies due to age restrictions, chose to self-fund their vaccinations.

Real-world impact and effectiveness of the quadrivalent HPV vaccine: an updated systematic literature review

INTRODUCTION

Human papillomavirus (HPV) infection, which poses significant disease burden, is decreasing following implementation of vaccination programs. Synthesized evidence on HPV vaccine real-world benefit was published in 2016. However, long-term impact of vaccination, and how vaccination programs influence infection rates and disease outcomes, requires further examination.

AREAS COVERED

We systematically reviewed observational studies on HPV vaccination within MEDLINE, EMBASE, and Google Scholar from 2016 to 2020, involving 14 years of follow-up data. We identified 138 peer-reviewed publications reporting HPV vaccine impact or effectiveness. Outcomes of interest included rates of infection at different anatomical sites and incidence of several HPV-related disease endpoints.

EXPERT OPINION

The expansion of HPV vaccination programs worldwide has led to a reduction in genital infection and significant decreases in incidence of HPV-related disease outcomes. Therefore, the WHO has set goals for the elimination of cervical cancer as a public health concern. To track progress toward this requires an understanding of the effectiveness of different vaccination initiatives. However, the impact on males, and potential benefit of gender-neutral vaccination programs have not been fully explored. To present an accurate commentary on the current outlook of vaccination and to help shape policy therefore requires a systematic review of available data.

Changes in HPV16/18 Prevalence among Unvaccinated Women with Cervical Intraepithelial Neoplasia in Japan: Assessment of Herd Effects following the HPV Vaccination Program

Since the human papillomavirus (HPV) vaccination program for Japanese girls aged 12–16 years began in 2010, vaccination uptake has been low in women born before 1993 but high (approximately 70%) in those born during 1994–1999. We previously compared the prevalence of vaccine types HPV16 and HPV18 in cervical intraepithelial neoplasia grade 1–3 (CIN1–3) or adenocarcinoma in situ (AIS) between vaccinated and unvaccinated cohorts and found direct protection effects among vaccinated women in Japan. In this study, we focused on changes in HPV16/18 prevalence among “unvaccinated” cohorts with CIN/AIS. We analyzed HPV16/18 prevalence among 5051 unvaccinated women aged <40 years, newly diagnosed with CIN/AIS during 2012–2021 for time trends. Declining trends in HPV16/18 prevalence over 9 years were observed in CIN1 (36.0–10.0%, Ptrend = 0.03) and CIN2–3/AIS (62.5–36.4%, Ptrend = 0.07) among women aged <25 years. HPV16/18 prevalence in CIN1 and CIN2–3/AIS diagnosed at age 20–24 years was lower in 1994–1999 birth cohorts compared with 1988–1993 birth cohorts (4.5% vs. 25.7% for CIN1 and 40.0% vs. 58.1% for CIN2–3/AIS, both p = 0.04). Significant reduction in HPV16/18 prevalence among young unvaccinated women with CIN1 and CIN2–3/AIS suggests herd effects of HPV vaccination in Japan.

Real-world impact and effectiveness assessment of the quadrivalent HPV vaccine: a systematic review of study designs and data sources

INTRODUCTION

Vaccine effectiveness and impact studies are typically observational, generating evidence after vaccine launch in a real-world setting. For human papillomavirus (HPV) vaccination studies, the variety of data sources and methods used is pronounced. Careful selection of study design, data capture and analytical methods can mitigate potential bias in such studies.

AREAS COVERED

We systematically reviewed the different study designs, methods, and data sources in published evidence (1/2007-3/2020), which assessed the quadrivalent HPV vaccine effectiveness and impact on cervical/cervicovaginal, anal, and oral HPV infections, anogenital warts, lesions in anus, cervix, oropharynx, penis, vagina or vulva, and recurrent respiratory papillomatosis.

EXPERT OPINION

The rapid growth in access to real-world data allows global monitoring of effects of different public health interventions, including HPV vaccination programs. But the use of data which are not collected or organized to support research also underscore a need to develop robust methodology that provides insight of vaccine effects and consequences of different health policy decisions. To achieve the WHO elimination goal, we foresee a growing need to evaluate HPV vaccination programs globally. A critical appraisal summary of methodology used will provide timely guidance to researchers who want to initiate research activities in various settings.

A nationwide birth year-by-year analysis of effectiveness of HPV vaccine in Japan

In Japan, the age‐adjusted incidence of cervical cancer has been increasing constantly and rapidly among younger women. We set out to accurately confirm the effectiveness of the HPV vaccine in Japan. Data were collected for women born in the fiscal year (FY) 1990 to 1997, who became eligible for their 20‐y‐old cervical cancer screening between the FY 2010 to 2017. The adjusted incidence of cervical intraepithelial neoplasia (CIN)1+ in women born in FY 1990 to 1993, that is those who reached the national vaccination target age prior to the introduction of publicly subsidized HPV vaccinations, referred here after as “the pre‐introduction generation”, was 1.42% (242/17 040). The incidence in the “vaccination generation” (women born in FY 1994 to 1997, that is those who were heavily vaccinated as a group when they were of the nationally targeted age of 13‐16) was 1.66% (135/8020). There was no significant difference between these incidence rates. However, our FY birth year‐by‐year analysis revealed that the incidence of CIN1+ was obviously lower than that predicted based on just the trend for CIN1+ seen in the pre‐introduction generation. Our analysis revealed that the incidence of CIN3+ was obviously lower in the vaccination generation than in the pre‐introduction generation (P = .0008). The incidence of CIN was already tending to increase in both the pre‐introduction and vaccination generations. The changes in CIN incidence by individual birth FY must be examined to accurately determine the actual effects of the HPV vaccine for reducing mild cervical lesions.

Effectiveness of HPV vaccination against the development of high-grade cervical lesions in young Japanese women

BACKGROUND

Although more than 10 years have passed since HPV vaccination was implemented, first as an interim programme (Emergent vaccine promotion programme) in November 2010, followed by incorporating into the National Immunization Programme in April, 2013 and suspended in June 2013, limited studies have investigated the HPV vaccine effectiveness against high-grade cervical lesions in Japan.

METHODS

We collected the matched data of the results of cervical biopsy and history of vaccination from the Japan Cancer Society database. The subjects were women aged 20 to 29 years screened for cervical cancer between April, 2015 and March, 2017, and with information on HPV vaccination status. We estimated the relative risk of developing high-grade cervical lesions in vaccinated subjects using Poisson regression as compared to unvaccinated subjects.

RESULTS

Among the 34,281 women screened, 3770 (11.0%) were vaccinated. The prevalence of CIN2+ was statistically significantly lower in the vaccinated women as compared to the unvaccinated women (Vaccine Effectiveness (VE) =76%; RR = 0.24, 95% CI:0.10-0.60). High VE against CIN3+ was also observed (91%; RR = 0.09, 95% CI:0.00-0.42).

CONCLUSION

Women aged 20-29 years who received at least one dose of HPV vaccine had a significantly lower risk of high-grade cervical lesions than those not vaccinated. In Japan, HPV vaccination should be resumed in order to reduce the incidence of cervical cancer.

Japan's Ongoing Crisis on HPV Vaccination

The Japanese government suspended proactive recommendations for the HPV vaccine in June 2013. The suspension is now in its seventh year, despite all the data pointing to the safety of the HPV vaccine. We reported a high vaccine effectiveness in the group of women vaccinated before their first intercourse (93.9%). The prevalence of cross-protected types of HPV 31/45/52 was also lower in the vaccinated group, and the vaccine effectiveness was 67.7%. Furthermore, prevalence of HPV16, 31 and 52 infection rates in the vaccinated group were obviously lower than that in the unvaccinated group, and no one had HPV18 or 45 infection in the vaccinated group. The addition of a cross-protective effect toward HPV types 31/45/52 to HPV types 16/18, which is the direct target of the bivalent HPV vaccine, may possibly prevent around 82% of invasive cervical cancer cases in Japan. With regard to the preventive effect of histological abnormalities, we also reported significant reduction in incidence of cervical intraepithelial neoplasia (CIN)3 or worse. Thus, the efficacy of the vaccine has been demonstrated for precancerous disease, and the diverse symptoms after HPV vaccination are likely functional somatic. For the future of Japanese girls, there is a need to resume the proactive recommendation of HPV vaccination and for immediate action to be taken by the Japanese government.

Bivalent Human Papillomavirus Vaccine Effectiveness in a Japanese Population: High Vaccine-Type-Specific Effectiveness and Evidence of Cross-Protection

Background

Proactive recommendations for human papillomavirus (HPV) vaccines in Japan have been suspended for 5 years because of safety concerns. While no scientific evidence exists to substantiate these concerns, one reason given for not reinstating recommendations is the lack of reliable vaccine effectiveness (VE) data in a Japanese population. This study reports the VE of the bivalent HPV vaccine in Japanese women aged 20–22 years.

Methods

During cervical screening between 2014 and 2016, women had Papanicolaou smears and HPV tests performed and provided data about their sexual history. Estimates of VE for vaccine-targeted HPV type 16 (HPV16) and 18 and cross-protection against other types were calculated.

Results

Overall, 2197 women were tested, and 1814 were included in the analysis. Of these, 1355 (74.6%) were vaccinated, and 1295 (95.5%) completed the 3-dose schedule. In women sexually naive at vaccination, the pooled VEs against HPV16 and 18 and for HPV31, 45, and 52 were 95.5% (P < .01) and 71.9% (P < .01), respectively. When adjusted for number of sex partners and birth year, pooled VEs were 93.9% (P = .01) and 67.7% (P = .01) for HPV16 and 18 and HPV31, 45, and 52, respectively.

Conclusions

The bivalent HPV vaccine is highly effective against HPV16 and 18. Furthermore, significant cross-protection against HPV31, 45, and 52 was demonstrated and sustained up to 6 years after vaccination. These findings should reassure politicians about the VE of bivalent HPV vaccine in a Japanese population.

Reduction in HPV16/18 prevalence among young women with high-grade cervical lesions following the Japanese HPV vaccination program

The Japanese government began a human papillomavirus (HPV) vaccination program for girls aged 12‐16 years in 2010 but withdrew its recommendation in 2013 because of potential adverse effects, leading to drastically reduced vaccination uptake. To evaluate population‐level effects of HPV vaccination, women younger than 40 years of age newly diagnosed with cervical intraepithelial neoplasia grade 1‐3 (CIN1‐3), adenocarcinoma in situ (AIS), or invasive cervical cancer (ICC) have been registered at 21 participating institutes each year since 2012. A total of 7709 women were registered during 2012‐2017, of which 5045 were HPV genotyped. Declining trends in prevalence of vaccine types HPV16 and HPV18 during a 6‐year period were observed in CIN1 (50.0% to 0.0%, P_trend < .0001) and CIN2‐3/AIS (83.3% to 45.0%, P_trend = .07) only among women younger than 25 years of age. Overall, HPV vaccination reduced the proportion of HPV16/18‐attributable CIN2‐3/AIS from 47.7% to 33.0% (P = .003): from 43.5% to 12.5% as routine vaccination (P = .08) and from 47.8% to 36.7% as catch‐up vaccination (P = .04). The HPV16/18 prevalence in CIN2‐3/AIS cases was significantly reduced among female individuals who received their first vaccination at age 20 years or younger (P = .02). We could not evaluate vaccination effects on ICC owing to low incidence of ICC among women aged less than 25 years. We found HPV vaccination to be effective in protecting against HPV16/18‐positive CIN/AIS in Japan; however, our data did not support catch‐up vaccination for women older than 20 years. Older adolescents who skipped routine vaccination due to the government’s suspension of its vaccine recommendation could benefit from receiving catch‐up vaccination before age 20 years.

Reduction in HPV 16/18 prevalence among young women following HPV vaccine introduction in a highly vaccinated district, Japan, 2008-2017

Objective: Human papillomavirus (HPV) vaccination was introduced in Japan in April 2013, as a national immunization program for girls aged 12–16 years, after an initial introduction in 2010 as a public-aid program for girls aged 13–16 years. The Yuri-Honjo district had the highest vaccine coverage among women aged 17–51 years in 2017, due to the original public-aid program. The aim of this study was to evaluate the differences in the vaccine types of HPV16/18 infections between 2008–2012 (pre-vaccine era) and 2013–2017 (vaccine era).

Materials and Methods: We evaluated whether HPV vaccination was associated with a decrease in the prevalence of HPV16/18 and high-risk HPV and the incidence of HPV-associated cervical lesions. A total of 1,342 women aged 18–49 years, covering both the pre-vaccine and vaccine eras, who visited Yuri Kumiai General Hospital and underwent HPV genotype tests from June 2008 to December 2017 were compared.

Results: Among women aged 18–24 years with higher vaccine coverage (68.2%), the prevalence of HPV16/18 and high-risk HPV decreased from 36.7% and 69.4%, respectively, in the pre-vaccine era to 5.8% and 50.0%, respectively, in the vaccine era (p=0.00013 and p=0.047, respectively). Among those with cervical intraepithelial neoplasia grade 2− and grade 2+, HPV16/18 prevalence decreased from 30.0% to 2.7% (p=0.0018) and from 81.8% to 36.4% (p=0.030), respectively. In this age group, the rate of HPV16/18 positivity decreased significantly. Among age groups with lower vaccine coverage, HPV prevalence did not significantly differ between the two eras.

Conclusion: The prevalence of HPV16/18 and high-risk HPV significantly decreased in women aged 18–24 years, most of whom were vaccinated. HPV vaccination effectively reduced the prevalence of HPV16/18 infections in the Yuri-Honjo district.

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.

Differential misclassification between self-reported status and official HPV vaccination records in Japan: Implications for evaluating vaccine safety and effectiveness

Japan has no national vaccine registry and approximately 1700 municipalities manage the immunization records independently. In June 2013, proactive recommendations for the human papillomavirus (HPV) vaccine were suspended after unconfirmed reports of adverse events following immunization in the media, despite no vaccine safety signal having been raised. Furthermore, studies assessing HPV vaccine safety and effectiveness published post suspension are predominantly based on self-reported information. Our aim was to examine the accuracy of self-reported vaccination status compared with official municipal records. Participants were women aged 20–22 yrs, who were attending for cervical screening in Niigata city. Among the 1230 eligible registrants, vaccine uptake, defined as any dose, was 75.0% and 77.2% according to a self-reported questionnaire and municipal records, respectively. The accuracy rate of self-reported information was as follows: positive predictive value (PPV) was 87.7%; negative predictive value (NPV) was 54.5%; sensitivity was 85.2%; and specificity was 59.8%. The validity of self-reported information was only moderate (Kappa statistic = 0.44, 95% confidence interval 0.37–0.50). This combined with the low NPV may lead to reduced estimation of effectiveness and safety. A more reliable method, such as a national HPV vaccine registry, needs to be established for assessing HPV immunization status in Japan.

Dynamic changes in Japan's prevalence of abnormal findings in cervical cervical cytology depending on birth year

Japan’s governmental recommendation of HPV vaccine has now been suspended for more than 4 years. In and before 2013, the targets of 20-year-old cervical cancer screening were females born in and before 1993, i.e., those who could not have received HPV vaccination because it was not yet publicly introduced. The targets during 2014–2019 are, or will be, those born in 1994–1999, i.e., those who came of age during a period with the highest HPV immunization rate. We analyzed the statistical data for each birth year, for the cumulative HPV vaccination rates achieved as of age 16, and for the corresponding results of cervical cancer screening at age 20. The rate of abnormal findings in cervical cytology increased slightly from 3.68% in 2010 (birth year: 1990) to 4.35% in 2013 (birth year: 1993); however, it dynamically dropped to 2.99% in 2014 (birth year: 1994) and 3.03% in 2015 (birth year: 1995). In total, the rate of abnormal findings in cervical cytology was 3.96% in 2010–2013, but significantly dropped to 3.01% in 2014–2015 (p = 0.014). This is the first description of dynamic changes occurring in the abnormal rate of cervical cancer screening as a result of positive changes in national HPV vaccination rates.

What information can change the attitude of teachers toward the human papillomavirus vaccine?

AIM

We conducted a self-administered survey on the perception of teachers toward human papillomavirus (HPV) vaccine to determine the ways to increase their willingness to encourage its use.

METHODS

Answers were obtained both prior to and after having the teachers read five brief information articles: (i) cervical cancer knowledge, (ii) vaccine knowledge, (iii) result of a survey in Nagoya, (iv) news report of the World Health Organization statement and (v) articles written by Dr Muranaka, a journalist.

RESULTS

Most of the respondents (180/247) did not know about the natural history of cervical cancer. Only 36% knew that HPV is the cause of cervical cancer, although 63% knew that HPV vaccine would prevent cervical cancer. Few respondents had knowledge regarding adverse events following immunization and the survey results from Nagoya. Among those who were initially negative for the HPV vaccine, only 43% revealed that they fully understood its safety and only 29% reversed their opinion to recommend vaccination to their daughters and/or students, even after reading our informational material. The most useful information for changing their attitudes was to increase their understanding of vaccines and informing them about Nagoya city survey results. They mostly wanted a proof of the preventive effects of the vaccine on cervical cancer in Japan.

CONCLUSION

Gynecologists and pediatricians must proactively communicate accurate scientific information to the government and the media to spread awareness among people in Japan. Also, we must try to demonstrate the capabilities of this vaccine to prevent cervical cancer and/or its precancerous lesions.

Multiple types of human papillomavirus infection and anal precancerous lesions in HIV-infected men in Taiwan: a cross-sectional study

OBJECTIVES

This study aimed to assess the relationship between infection with multiple human papillomavirus (HPV) types and abnormal anal cytology in HIV-infected men.

DESIGN

An observational, cross-sectional study.

SETTING

A regional referral hospital in Taiwan.

PARTICIPANTS

In total, 714 HIV-infected men were enrolled between March 2011 and June 2016. Thin preparation anal Pap smears were interpreted according to the 2001 Bethesda System. Thirty-seven types of HPV were detected by reverse line blotting, including 13 oncogenic types and 24 non-oncogenic types.

OUTCOME MEASURES

The relationship between anal HPV infection and abnormal anal cytology in people of Asian ethnicity and the coverage efficacy in HPV-vaccinated HIV-infected men.

RESULTS

On anal cytology, 175 (24.5%) subjects had atypical squamous cells of undetermined significance (ASCUS) or higher grades of dysplasia, including 87 (49.7%) with ASCUS, 73 (41.7%) with low-grade squamous intraepithelial lesions (LSILs) and 15 (8.6%) with high-grade squamous intraepithelial lesions (HSILs). A higher proportion of subjects with those without LSIL/HSIL (93.1% vs 67.3%, P<0.0001) had multiple HPV types. The odds of having LSIL/HSIL increased with an increasing number of HPV types: the ORs ranged from 1 for no HPV types to 6.96 (95% CI 2.38 to 20.37) for more than five types (P_trend <0.0001). Multivariate logistic regression analysis showed a significant association between LSIL/HSIL and the number of HPV genotypes present (OR 1.20; 95% CI 1.02 to 1.42, P<0.05). HPV types covered by the nonavalent HPV vaccine (types 6/11/16/18/31/33/45/52/58) were detected in 70.1% of the patients in this study.

CONCLUSIONS

The odds of having anal LSIL/HSIL are approximately seventimes greater in HIV-infected men with than withoutsix or more types of HPV. Multiple HPV types in HIV-infected patients deserves aggressive follow-up, and HPV vaccination programme require scaling up.

Preventive effect of human papillomavirus vaccination on the development of uterine cervical lesions in young Japanese women

AIM

To examine the effect that human papillomavirus (HPV) vaccination has had in Akita Prefecture, by comparing cervical cytology results from women aged 20-24 years with or without HPV vaccination.

METHODS

We examined cervical cytology results from 2425 subjects who underwent cervical cancer screening under the jurisdiction of the Akita Foundation for Healthcare between January 2014 and October 2016. We compared the prevalence of cytologic abnormalities among women aged 20-24 years with or without HPV vaccination.

RESULTS

The rate of atypical squamous cells of undetermined significance (ASC-US) or worse was 0.242% (1/413) with HPV vaccination, and 2.04% (41/2012) without HPV vaccination. Overall, the prevalence of abnormal cytology results was significantly lower in women aged 20-24 years who had received an HPV vaccination than in those who had not (P = 0.011). The reduction in the rate of abnormal cervical cytology results by HPV vaccination was 88.1%.

CONCLUSION

Within a 4-year-5-year period following vaccination, women aged 20-24 years who received an HPV vaccination had significantly lower rates of abnormal cervical cytology results than those who did not receive the vaccine.

Realistic fear of cervical cancer risk in Japan depending on birth year

Objective: In Japan, the possible adverse events upon HPV vaccination was widely reported in the media. MHLW announced the suspension of aggressively encouraging HPV vaccination in 2013, and inoculation rate has sharply declined. The aim of the present study was estimation of future cervical cancer risk.

Methods: The latest data on vaccination rate at each age in Sakai City were first investigated. The rate of experiencing sexual intercourse at the age of 12, 13, 14, 15, 16, 17 and throughout lifetime is assumed to be 0%, 1%, 2%, 5%, 15%, 25%, and 85% respectively. The cervical cancer risk was regarded to be proportional to the relative risk of HPV infection over the lifetime. The risk in those born in 1993 whom HPV vaccination was not available yet for was defined to be 1.0000.

Results: The cumulative vaccination rates were 65.8% in those born in 1994, 72.7% in 1995, 72.8% in 1996, 75.7% in 1997, 75.0% in 1998, 66.8% in 1999, 4.1% in 2000, 1.5% in 2001, 0.1% in 2002, and 0.1% in 2003. The relative cervical cancer risk in those born in 1994–1999 was reduced to 0.56–0.70, however, the rate in those born in 2000–2003 was 0.98–1.0, almost the same risk as before introduction of the vaccine.

Discussion: The cumulative initial vaccination rates were different by the year of birth. It is confirmed that the risk of future cervical cancer differs in accordance with the year of birth. For these females, cervical cancer screening should be recommended more strongly.