Changing trends in HPV vaccination in Japan

Regional disparities in measles vaccination coverage and their associated factors: an ecological study in Japan

BACKGROUND

The decline in measles vaccination coverage is a global concern. In Japan, coverage of the first-dose of measles vaccine, which had exceeded the target of 95.0% since fiscal year (FY) 2010, fell to 93.5% in FY 2021. Vaccination coverage increased to 95.4% in FY 2022 but varied by municipality. Few studies have focused on regional disparities in measles vaccination coverage. This study aimed to clarify the regional disparities in measles vaccination coverage by municipality in Japan and their associated factors.

METHODS

In this ecological study, the measles vaccination coverage in FY 2022; population density; area deprivation index (ADI, an indicator of socioeconomic status); proportion of foreign nationals, single-father households, single-mother households, and mothers aged ≥30 years; and number of medical facilities, pediatricians, and non-pediatric medical doctors in 1,698 municipalities were extracted from Japanese government statistics. Negative binomial regression was performed with the number of children vaccinated against measles as the dependent variable, number of children eligible for measles vaccination as the offset term, and other factors as independent variables.

RESULTS

Vaccination coverage was less than 95.0% in 54.3% of municipalities. Vaccination coverage was significantly positively associated with population density and negatively associated with the proportion of single-father households, mothers aged ≥30 years, and the ADI (incidence rate ratio [IRR]: 1.004, 0.976, 0.999, 0.970, respectively).

CONCLUSION

This study showed regional disparities in measles vaccination coverage in Japan. Single-father households, age of mothers, and socioeconomic status may be key factors when municipalities consider strategies to improve vaccination coverage.

A comprehensive narrative review of challenges and facilitators in the implementation of various HPV vaccination program worldwide

INTRODUCTION

Cervical cancer has been considered as one of the most common cancers in women (15-44 years) globally, but the advent of the human papilloma virus (HPV) vaccine has raised the anticipation that eradication of cervical carcinoma might be achieved in the near future as several prophylactic cervical carcinoma vaccines have already been currently licensed in various countries. Countries should devise strategies, practices and policies to attain and sustain higher levels of HPV immunization coverage as still 68% countries have introduced HPV vaccine in their national immunization programs even after 17 years following the licensure of the first prophylactic HPV vaccine.

METHODOLOGY

A comprehensive literature analysis was conducted using various databases and search engines, to include the most relevant research articles and data available and critically discussed the operational gaps that need to be answered to achieve adequate coverage of HPV vaccination.

RESULTS

The present review highlights the existing HPV vaccination strategies, unmet needs and challenges needed to be addressed for proper implementation framework as well as the collaborations required to achieve decent vaccination coverage. Well-coordinated vaccination strategy with focus on adolescent girls and if possible, boys can lead to dramatic impact on disease reduction around the world.

Evaluating the cost-effectiveness of HPV vaccination for adolescent girls in Japan: A comparison of 2-valent, 4-valent, and 9-valent HPV vaccines with consideration of cross-protection

OBJECTIVE

In April 2023, the Japanese Health Ministry panel approved the inclusion of the 9-valent human papillomavirus (9vHPV) vaccine in the National Immunization Program, alongside the 2-valent (2vHPV) and 4-valent HPV (4vHPV) vaccines. In response to this, we evaluated the cost-effectiveness of these three vaccines for routine immunization of girls aged 12-16 in Japan, considering the cross-protection of 2vHPV and 4vHPV vaccines.

METHODS

We constructed an age-structured mathematical model for HPV transmission, aiming to quantify the economic and epidemiological effects of various HPV vaccination strategies over a 70-year period in Japan. We determined incremental costs and quality-adjusted life years (QALYs) for each strategy, applying a 3% annual discount. Univariate and probabilistic sensitivity analyses were conducted to assess the uncertainty of our model results, with all evaluations done in 2023.

RESULTS

Our projections indicate that the HPV vaccination program in Japan will significantly reduce the incidence of HPV-related diseases. All HPV vaccination strategies, using the 2vHPV, 4vHPV, and 9vHPV vaccines, were found to be cost-effective compared to no vaccination, with incremental cost-effectiveness ratios of ¥971,447/QALY, ¥1,237,297/QALY, and ¥742,084/QALY, respectively. Direct comparisons between vaccines demonstrated that the 9vHPV vaccination was more cost-effective than the 2vHPV vaccination, whereas 4vHPV vaccination was dominated by 2vHPV vaccination.

CONCLUSIONS

Our study validates the cost-effectiveness of implementing the 9vHPV vaccine as the primary option over the 2vHPV or 4vHPV vaccine for girls in Japan. These findings underscore the need to improve the acceptance rate and coverage of HPV vaccinations in the country.

Adverse events from HPV vaccination in Taiwan

The safety of human papillomavirus (HPV) vaccines has been evaluated continuously in pre-licensure clinical trials, post-marketing surveillance systems, and observational studies. Most studies have found no significant association between serious adverse events and HPV vaccination. However, these studies have focused on Western populations; similar studies focusing on Asian populations are insufficient. Our retrospective cohort study used the HPV-vaccination records of junior high-school adolescent girls aged 12-15 years between 2013 and 2018 in Taiwan's National Immunization Information System and linked them to a registry for beneficiaries in Taiwan's National Health Insurance Database (NHID) to establish the vaccinated group. We selected 19 serious diseases as serious adverse events. We compared the incidence rates of these serious adverse events between the vaccinated group and girls in the same age group population, and we calculated the standardized incidence ratio (SIR) to evaluate the risk of serious adverse events after HPV vaccination. Because of the onset of different types of diseases, we set three periods after the subjects received HPV vaccination: within 3 months, within 1 year, and during the study period (2013-2018). The results showed the incidence rates and the SIRs of 19 selected adverse events. Among the 19 selected serious adverse events, the disease with the highest incidence rate during the study period was fibromyalgia (73.23 cases per million population), and the disease with the lowest incidence rate during the study period was Crohn's disease (0.15 cases per million population). The results showed no statistically significant increases in the risk of 19 selected serious adverse events and indicated no association between HPV vaccination and serious adverse events. Given the benefits and safety of HPV vaccination, our research can reduce concerns about vaccine side effects, inform health policies and improve public and clinician's acceptance of HPV vaccine policy.

Adverse Events Following Immunization- The Known Unknowns and Black Box : Based on 10th Dr. I. C. Verma Excellence Award for Young Pediatricians Delivered as Oration on 9th Oct. 2022

Although vaccines are one of the most rigorously tested biological products, the safety concerns persist globally. The vaccine safety concerns linked to measles, pentavalent and human papillomavirus (HPV) vaccines have affected the vaccine coverage significantly in past. While surveillance of adverse events following immunization (AEFI) is part of the national immunization program mandate, it suffers from challenges and biases related to reporting, completeness, and quality. Some conditions of concern, termed as adverse events of special interest (AESI) following vaccination, mandated specialised studies to prove/disprove the association. The AEFIs/AESIs are usually caused by one of the four pathophysiologic mechanisms, but for several AEFIs/AESIs, the exact pathophysiology remains elusive. For the causality assessment of AEFIs, a systematic process with checklists and algorithm are followed to classify into one of the four causal association categories. While the causal association primarily banks on epidemiological observations for several AEFIs, the emerging evidences indicate roles of underlying genetic, gender, age and other pro-inflammatory risk factors for AEFIs and AESIs. The emerging evidences suggest role of antigenic mimicry, autoantibody(ies) and underlying genetic susceptibility for the AEFIs/AESIs. The uncertainty about the frequency, profile, interval, and severity of AEFIs/AESIs and variations across the population, ambiguity about the exact pathophysiology mechanism, absence of definite markers, suggest a possible black box effect of the vaccines. Unless these unanswered questions concerning the AEFIs/AESIs are addressed appropriately and communicated to the stakeholders (professionals, care providers, beneficiaries, general public and media), the anti-vaccine movement shall keep challenging the vaccine and vaccination program.

Patterns of HPV vaccine hesitancy among catch-up generations in Japan: A descriptive study

BACKGROUND

Cervical cancer is a preventable disease caused by human papillomavirus (HPV). The HPV vaccine uptake in Japan has been slow since the Ministry of Health, Labour and Welfare suspended the recommendation for proactive HPV vaccination in 2013. In April 2022, Japan initiated catch-up vaccinations for women who missed the opportunity to receive the HPV vaccine. However, as of September 2022, very few women had received catch-up vaccination, raising concerns about vaccine hesitancy in the target population. It is necessary to understand the thinking and motivation of the target population to develop effective strategies to improve vaccination rates. Therefore, using cluster analysis, this study aimed to clarify the pattern of HPV vaccine hesitancy among the catch-up generations in Japan.

METHODS

This descriptive study was based on an Internet survey completed by 3,790 women in Japan aged over 18 years who were eligible for catch-up vaccination and had not yet received an HPV vaccine. Participants were asked about their intention and thinking about the HPV vaccine and descriptive norms on vaccination intention. Cluster analysis using k-means clustering was performed to clarify these patterns.

RESULTS

Cluster analysis revealed three hesitancy patterns: acceptance, neutral and refusal. The acceptance group, with high intention, comprised 28.2% of the participants, and students and a high-income level mainly dominated this group. The refusal group, with negative thinking and low intention, accounted for 20.1% and was more prevalent among workers and the unemployed. The neutral group, with neutral thinking and intention, accounted for 51.6%. The perceived effect of descriptive norms on vaccination intention was large in the acceptance group but small in the refusal group.

CONCLUSION

HPV vaccine awareness promotion strategies must be based on the characteristics of each group and the different distributions of sociodemographic factors.

Health impact and cost effectiveness of implementing gender-neutral HPV vaccination in Japan

OBJECTIVE

To assess the public health impact and cost effectiveness of gender-neutral vaccination (GNV) versus female-only vaccination (FOV) with human papillomavirus (HPV) vaccination in Japan.

METHODS

We modeled the public health impact and cost effectiveness of GNV versus FOV to prevent HPV-associated diseases in Japan over the next 100 years. We used one-way sensitivity analyses to examine the impact of varying key model input parameters and conducted scenario analyses to explore the effects of varying the vaccination coverage rate (VCR) of each cohort.

RESULTS

In the base-case analysis, GNV averted additional cancer cases (17,228 female/6,033 male) and deaths (1,892 female/1,849 male) compared to FOV. When all HPV-associated diseases were considered, GNV had an incremental cost-effectiveness ratio of ¥4,732,320 (US$35,987)/quality-adjusted life year gained compared to FOV. The model was most sensitive to the discount rate and the disutility associated with HPV-related diseases. GNV had greater relative public health benefits when the female VCR was lower and was cost effective at a female VCR of 30%.

CONCLUSIONS

Immediate implementation of GNV would reduce the disease burden and mortality associated with HPV in Japan, and would be cost effective compared to FOV if the female VCR remains low (30%).

Resumption of active recommendation of the human papillomavirus vaccine in Japan and future challenges for the National Immunization Program

Japan's immunization program resumed proactively recommending the use of the human papillomavirus (HPV) vaccine nationwide in April 2022, after suspending this recommendation in June 2013. The promotion of catch-up vaccinations is an urgent issue to reduce the increase in cervical cancer and other cancers caused by low vaccination rates. In addition, the National Immunization Program still has issues to be considered, such as the adoption of the 9-valent vaccine, establishment of an appropriate number of vaccinations according to age, and routine immunization of males. There is a history of eliminating the use of the measles, mumps, and rubella vaccine and the mouse brain-derived, purified inactivated Japanese encephalitis vaccine, as well as suspending the HPV vaccine recommendation in Japan. These decisions have led to the current preventable infectious disease burden. In order to make the right policy decisions based on science-based assessments, it is necessary to establish a safety assessment platform to evaluate the causal relationship between vaccines and adverse events following immunization. Information technology, which has been promoted with the coronavirus disease 2019 vaccine in the current pandemic, may assist in providing more detailed vaccine safety evaluations for other vaccines.

The 'best friend effect': a promising tool to encourage HPV vaccination in Japan

BACKGROUND

In Japan, HPV vaccination rates has dramaticaly declined since 2013. Since mothers are the ones making the decision to vaccinate their daughters against HPV, we probed the mothers' intention to receive vaccinations for themselves and to vaccinate their daughters against HPV, and their reasoning.

METHODS

An internet survey was conducted in March of 2021. Through the screening, 1576 participants were extracted from a survey panel and divided into 3 groups based on their daughter's birth fiscal year (Group 1: 1994 to 1999, Group 2: 2000 to 2003, Group3: 2004 to 2008). The chi-square test and residual analysis were used for the statistical analysis of comparison among the groups. Logistic regression analysis was used to identify independent variables with mothers intention to get their daughters vaccinated under specific situations.

RESULTS

The percentage of respondents without anxiety regarding their daughter's general vaccination was significantly higher in Group 1 (p < 0.05). In the mothers of daughters born in or after 2000 when vaccination rates declined (Groups 2 and 3), a situation in which 'The daughter's best friends were vaccinated before her' made the mothers think positively about HPV vaccination, and to the same degree as a situation in which 'You received a notice from your local government recommending vaccination' (Group 2: 41.6% (214/514) and 40.5% (208/514), Group 3: 48.5% (257/530) and 47.0% (249/530)).

CONCLUSION

If mothers who have had their daughters vaccinated were to recommend HPV vaccination to their close friends, 'the best friend effect' should promote others to be vaccinated.

Effect of a web-based cervical cancer survivor story on the willingness and behavioral change for Human Papillomavirus Vaccination among Japanese parents with at least one daughter aged 11 to 18 years old: Randomized Controlled Trial

Background

Providing adequate information to parents who have children eligible for human papillomavirus (HPV) vaccination is essential to overcoming vaccine hesitancy in Japan, where the government recommendation has been suspended. However, prior trials assessing the effect of brief educational tools have shown only limited effects on increasing the willingness of parents to vaccinate their daughters.

Objective

The aim of this trial is to assess the effect of a cervical cancer survivor’s story on the willingness of parents to get HPV vaccination for their daughters.

Methods

In this double-blinded, randomized controlled trial (RCT) implemented online, we enrolled 2175 participants aged 30-59 years in March 2020 via a webpage and provided them with a questionnaire related to the following aspects: awareness regarding HPV infection and HPV vaccination, and willingness for HPV vaccination. Participants were randomly assigned (1:1) to see a short film on a cervical cancer survivor or nothing, stratified by sex (male vs female) and willingness for HPV vaccination prior to randomization (yes vs no). The primary endpoint was the rate of parents who agreed for HPV vaccination for their daughters. The secondary endpoint was the rate of parents who agreed for HPV vaccination for their daughters and the HPV vaccination rate at 3 months. The risk ratio (RR) was used to assess the interventional effect.

Results

Of 2175 participants, 1266 (58.2%) were men and 909 (41.8%) were women. A total of 191 (8.8%) participants were willing to consider HPV vaccination prior to randomization. Only 339 (15.6%) participants were aware of the benefits of HPV vaccination. In contrast, 562 (25.8%) participants were aware of the adverse events of HPV vaccination. Although only 476 (21.9%) of the respondents displayed a willingness to vaccinate their daughters for HPV, there were 7.5% more respondents in the intervention group with this willingness immediately after watching the short film (RR 1.41, 95% CI 1.20-1.66). In a subanalysis, the willingness in males to vaccinate daughters was significantly higher in the intervention group (RR 1.50, 95% CI 1.25-1.81); however, such a difference was not observed among females (RR 1.21, 95% CI 0.88-1.66). In the follow-up survey at 3 months, 1807 (83.1%) participants responded. Of these, 149 (8.2%) responded that they had had their daughters receive vaccination during the 3 months, even though we could not see the effect of the intervention: 77 (7.9%) in the intervention group and 72 (8.7%) in the control group.

Conclusions

A cervical cancer survivor’s story increases immediate willingness to consider HPV vaccination, but the effect does not last for 3 months. Furthermore, this narrative approach to parents does not increase vaccination rates in children eligible for HPV vaccination.

Trial Registration

UMIN Clinical Trials Registry UMIN000039273; https://tinyurl.com/bdzjp4yf