学位論文内容の要旨（ Summary of dissertation）

博士の専攻分野の名称

博士（医 学）（Degree conferred: Doctor of Philosophy）

氏 名

シャロン J. B. ハンリー

（Name of recipient: Sharon J.B. Hanley）

学 位 論 文 題 名（Title of dissertation）
Barriers to and Predictors of Human Papillomavirus (HPV) Vaccine Acceptance in Parents of AdolescentGirls: Maximizing the Public Health Impact of HPV Vaccination in Japan(思春期の娘を持つ親の子宮頸がん予防 HPV ワクチンに対する認知と受容：接種率向上のための要因解明)
Introduction:
Cervical cancer, caused by persistent infection with an oncogenic human papillomavirus (HPV), is highly
preventable, yet it claims the life of 275,100 women annually. Two highly effective prophylactic HPV
vaccines have been developed. Both contain antigens against HPV types 16 and 18, responsible for around
70% of cervical cancers worldwide. HPV vaccines offer promising new options in future cervical cancer
prevention programs. However, for the public health impact to be fully realized, high uptake is necessary.
Since HPV is transmitted sexually, the vaccine should ideally be administered before sexual debut.
Consequently, the primary target age group for vaccination is pre/adolescent girls. In this age group mostcountries require parental consent, so understanding parental attitudes towards HPV vaccine is essential.
For this reason, many studies on parental attitudes towards and acceptance of HPV vaccination have takenplace, both in Europe/North America and Asia. However, no such study has taken place in Japan.
In Japan, cervical cancer is the most common cancer in women aged 20-39yrs and the incidence isincreasing. In women aged 20-29yrs and 30-39yrs, HPV 16 and 18 are responsible for 90% and 76% of all
cervical cancer cases, respectively. Thus HPV vaccines offer a unique opportunity to reduce morbidity andmortality associated with cervical cancer in Japanese women of reproductive age. However, for high uptake
rates to be achieved, the vaccine must be both affordable and acceptable to those who influence uptake
most. Consequently, this study was designed to: (i) determine attitudes towards and knowledge of HPV andHPV vaccines, as well as the overall acceptance of HPV vaccination in Japanese parents, (ii) evaluate theinfluence of written educational information about HPV on parental acceptability of HPV vaccination,
particularly in areas of low cervical screening uptake and (iii) identify socio-demographic and attitudinal
predictors associated with HPV vaccine acceptance, in particular mothers cervical cancer screening history.
Materials and Methods:
Study 1 A 103-item survey instrument that assessed parental attitudes towards childhood vaccinations,socio-demographic factors, knowledge about and attitudes towards cervical cancer, HPV and the HPV
vaccination, willingness to pay for HPV vaccine, as well as information on cervical screening history andHPV related diseases was distributed to 2192 primary caregivers with daughters aged 11–14yrs, attending 5elementary (n=560) and 14 junior high schools (n=1632) in Sapporo between July and September 2010.
Surveys were sent out via the schools and returned to the main researcher by post. Independent predictors

of parental HPV vaccine acceptability were determined using multivariable logistic regression models.
Study 2: A randomized intervention study within a cross-sectional survey was conducted in two cities:
Sakata in Yamagata prefecture which has cervical cancer screening rates of around 55% and Kitami,Hokkaido, which has cervical cancer screening rates of around 7%. Subjects were 3471 primary caregivers
with daughters aged 11–14yrs, attending 15 elementary (n=769) and 7 junior high schools (n=817) inSakata and 18 elementary (n=914) and 11 junior high schools (n=971) in Kitami between October andDecember 2010. In addition to the survey instrument used in study 1, a random half of participants received
a detailed “HPV Information Sheet” about HPV and cervical cancer. Independent predictors of parental
HPV vaccine acceptability were determined using multivariable logistic regression models.
Results:
Since 98.5% of respondents were mothers, data from mothers and fathers was analyzed separately.
Results 1 (Study 1, mothers): Responses from 862 participants were analyzed. Around 93% of mothers
would accept the vaccine for their daughter if free, but only 1.5% was willing to pay the minimum
recommended price of ¥40,000. Vaccine acceptance was higher in mothers who had heard of HPV vaccine(aOR:2.58; CI:1.47–4.53), and who believed susceptibility to (aOR:2.30; CI:1.34–3.92) and severity of(aOR:3.73; CI:1.41–9.88) HPV to be high. Recommendations from a doctor (aOR:12.60; CI :7.06–21.48)
were also positively associated with increased HPV vaccine acceptance. Concerns about side effects ofboth the HPV vaccine (aOR:0.03; CI:0.01–0.08) and routine childhood vaccines in general (aOR:0.11;CI :0.02–0.78) emerged as barriers to vaccination. Not participating in routine cervical screening also
emerged as a deterrent (aOR:0.49; CI:0.27–0.91).
Results 2 (Study 2, mothers): Responses from 1032 participants were analyzed. Vaccine acceptability
was similar to that of survey 1, around 92% if offered for free and 1.5% at the recommended price.
Providing written educational material did not increase acceptability. Furthermore, participating in regularcervical screening (aOR:1.89; CI:1.10-3.25) was associated with positive acceptance of HPV vaccinationand concerns about vaccine safety (aOR:0.57; CI:0.36-0.91) was a barrier. However, the greatest barrier toHPV vaccination acceptance was living in an area with low cervical screening uptake (aOR:0.51;CI:0.31-0.84).
Results 3 (Studies 1 and 2, fathers): Responses from 27 fathers (16 divorced, widowed or single; 11married or cohabiting) were analyzed. Only one (3.7%) participant believed he had been previously been
infected with HPV and most (81.4%) believed their future risk was low. No differences existed according tomarital status. However, single fathers were significantly more likely than married fathers to believe theirdaughter was at risk for HPV (87.5% versus 36.4%; p=0.01) and cervical cancer (75.0% versus 27.3%;
p=0.02). Acceptability of free HPV vaccination was similar to that of mothers at 92% with no difference
according to marital status. However single fathers were significantly more likely (p=0.005) to pay morewhen vaccination came at a cost. Concerns specific to single fathers included explaining the sexual natureof HPV and having to take a daughter to a gynecologist to be vaccinated.
Conclusions:
The results of this first study investigating attitudes towards and acceptance of HPV vaccination inJapanese parents of adolescent girls are encouraging. Acceptance is high, when cost is not a barrier. Theysuggest that if physicians actively address safety concerns and are aware of issues specific to single fathers,
high uptake can be achieved in a publically funded HPV vaccination program. They do also indicate,however, that further research is needed to investigate whether lower vaccine acceptance in mothers who
do not undergo regular cervical screening is also reflected in actual uptake rates, since widespreaddisparities in cervical cancer could result.
Funding: This study was funded by a Grant-in-Aid from the Japanese Ministry of Education, Culture,Sports, Science and Technology. Main researcher: Sharon J.B. Hanley