Background: Although already approved for use in males in some jurisdictions, there is little information about parental attitudes toward having their sons receive the human papillomavirus (HPV) vaccine. The goal of this study was to ascertain parental intentions to vaccinate their sons with an HPV vaccine and to determine factors that predict this intention.
Methods: Parents of children aged 8–18 years were recruited from across Canada through random digit dialling. Participants were asked to respond to a series of questions in the context of a Grade 6 (age 11/12 years old), publicly funded school-based HPV vaccine programme, including their intention to vaccinate their sons with the HPV vaccine. Parents were also asked about a series of characteristics thought to predict intention to vaccinate as well as demographic characteristics. Backwards logistic regression was conducted to calculate adjusted odds ratios (AOR) to identify the factors that are predictive of parents’ intention to vaccinate their son(s) against HPV.
Results: Of the 1381 respondents with male children, 67.8% (95% CI 65.3 to 70.3) intend to vaccinate their son(s) against HPV. Parents who had positive attitudes toward vaccines and the HPV vaccine in particular (AOR 41.5, 95% CI 9.5 to 181.7), parents who were influenced by subjective norms (AOR 7.8, 95% CI 5.8 to 10.5), parents who felt that the vaccine had limited influence on sexual behaviour (AOR 2.3, 95% CI 1.6 to 3.3) and parents who were aware of HPV (AOR 1.4, 95% CI 1.1 to 2.0) were significantly more likely to report an intention to vaccinate boys against HPV. In contrast, residence in British Columbia compared to Atlantic Canada (AOR 0.4, 95% CI 0.2 to 0.8) and higher education (AOR 0.7, 95% CI 0.5 to 0.9) were negatively associated with intention to vaccinate. Parents who reported an intention to vaccinate their daughters were also highly likely to report an intention to vaccinate their sons (κ = 0.9, p<0.001).
Discussion: The majority of Canadian parents would intend to have their male children receive the HPV vaccine in the context of a publicly funded school-based immunisation programme. Overall attitudes toward vaccine, recommendations from health professionals and impact of the vaccine on sexual practices are important predictors of intention to have a male child receive the HPV vaccine.
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Although well understood to be a highly prevalent sexually transmitted virus for both men and women,1 2 the role and acceptability of the currently available human papillomavirus (HPV) vaccine to prevent HPV infection in boys and men remains unclear. Men are at risk for acquisition of both low risk HPV types, mostly responsible for genital warts, and high risk HPV types, responsible in part for development of anal and other HPV associated cancers. Men are also able to spread oncogenic HPV virus to women without having disease manifestations themselves.3 4 The efficacy of the HPV vaccine in preventing acquisition and development of HPV-related lesions in men is not yet known, but is being examined in ongoing clinical trials.3 However, it has been shown that young men demonstrate significant antibody responses to the HPV vaccine comparable to the responses seen in women.5 6 Because HPV is a sexually acquired virus, and because it is necessary for the HPV vaccine to be received prior to HPV exposure for it to offer a preventive benefit against HPV infection and cervical cancer, mathematical modelling and economic analyses have demonstrated that the maximum benefit from the vaccine is obtained when population-based HPV vaccine strategies are targeted to adolescents prior to their sexual debut, likely before the age of 12 years.7 8
In Canada, the HPV vaccine Gardasil was approved in August 2006 for young women aged 9–26 years,9 and in February 2007 the Canadian National Advisory Committee on Immunizations recommended the HPV vaccine for all women aged 9–26 years,10 with an emphasis on vaccinating young women prior to sexual debut. Currently, three provinces have publicly funded school-based HPV vaccine programmes for young women and additional provinces will be embarking on programmes for young women in September 2008.11 To date, given the lack of clinical efficacy data for the HPV vaccine in men, the HPV vaccine has not been approved or recommended for males in Canada, although some jurisdictions such as Australia have done so.4 However, given the burden of illness of HPV in men, and the strong serological response of young men to the HPV vaccine, the HPV vaccine will likely offer a benefit to males as well. In anticipation of this approval, it will be important to determine if parents are willing to vaccinate their sons with the HPV vaccine, given concerns that have been raised about the acceptability to recipients and parents.12 The goal of this study was to ascertain parental intentions to vaccinate their sons against HPV in Canada and to determine factors that predict parental intention to vaccinate their sons against HPV.
Men and women who were parents of children between the ages of 8–18 years, were at least 19 years of age and could respond to questions in English or French were invited to participate. Participants were recruited from across Canada between June 2006 and March 2007 through random digit dialling. Participants were offered an opportunity to participate in a draw for a gift.
Development of survey tool
The survey was based on the “Theory of Planned Behaviour” (TPB),13 and the tool was developed through an extensive literature search of factors that impact on vaccine behaviour14–22 and through an elicitation survey of parents to determine the key beliefs and attitudes in the intention to immunise a child against HPV. Ten parents pilot-tested a draft survey and provided feedback on content, comprehension and domains of relevance. The final survey was translated into French and back-translated into English, with no significant errors noted.
Demographic items assessed included age, gender, region of residence, education level, cultural background, religious affiliation and family composition of the respondent. Age(s), number of and gender of children along with adherence to childhood vaccination schedules were determined. Knowledge of cervical cancer and HPV at the start of the survey was assessed using a seven point Likert scale (strongly disagree 1, neutral 4 and strongly agree 7). A trained interviewer then provided standardised information to participants on HPV, the HPV vaccine, role of HPV in cervical cancer and genital warts, the nature of HPV transmission and the efficacy of the HPV vaccine as it related to cervical cancer prevention. Parents were informed that both men and women could become infected with HPV. As most jurisdictions in Canada have publicly funded vaccine programmes for adolescents that are delivered in the school setting, participants were next asked to respond to a series of questions regarding a Grade 6 (age 11/12 years) HPV vaccine programme in this context, including their intention to vaccinate their son(s) or daughter(s) with the HPV vaccine. Intention to vaccinate was measured using a seven point Likert scale as described earlier. Participants were asked about four specific psychological constructs that could predict parental intention to have their son receive the HPV vaccine. These constructs included i) attitudes toward vaccines in general and the HPV vaccine in particular, ii) subjective norms about HPV vaccination (perceptions of others’ preferences about whether one should vaccinate their daughter), iii) perceived behavioural control over HPV vaccination (perceptions about the relative ease or difficulty of vaccinating their son against HPV) and iv) attitudes toward the influence of HPV vaccination on sexual behaviour of adolescents. These four constructs were assessed using seven point Likert scales with between two and six items per construct.
Parental intention to have children undergo HPV vaccination has been estimated at 70%.12 23 24 Thus, to generate a national estimate of parental intention to vaccinate children against HPV with a 95% confidence interval (CI) of 3%, at least 896 participants were needed.25
Item reliability was established for psychological construct scales using Cronbach’s α, where a value of greater than 0.6 indicates acceptable internal consistency, and mean values for each scale were calculated. For scale items, aggregated scale scores were dichotomised with a mean value of 4.5 as a cutoff, with scores 4.5 or greater indicating a general positive value (that is, a positive attitude, perception of behavioural control or subjective norm). Descriptive analyses of sample demographics were conducted. Bivariate analyses were conducted comparing the responses of parents who intended to vaccinate their son(s) against HPV to those who would not vaccinate. For these remaining analyses, intention to vaccinate was defined as a response of 5 or greater on the Likert scale to the statement: “I intend to have my son(s) receive the HPV vaccine (once it becomes available)”. Respondents who did not agree or were neutral were coded as not intending to vaccinate. Variables that achieve p<0.05 were offered for inclusion in a multivariable model to achieve a best fit model. Backwards logistic regression was conducted to calculate adjusted odds ratios (AOR) to identify the factors that were predictive of parents’ intention to vaccinate their son(s) against HPV. Analysis was conducted with SPSS version 14.0 for Windows.
Between June 2006 and March 2007, 32 834 calls were made to in-service phones across Canada. Of the 23 969 homes that answered within four calls, 3979 had eligible candidates, 2109 (53.0%) consented to participate and 2083 completed the survey. A summary of the respondent characteristics is provided in table 1. Seventy-four per cent of the respondents were female and over 90% had three children or fewer. Over 50% of participants had heard of HPV and 27% knew that HPV was transmitted through sexual contact. Internal reliability of psychological construct subscales with Cronbach’s α and mean value with standard deviation of subscales was 0.8 and 5.8 (0.8) (attitudes toward vaccines), 0.9 and 5.1 (1.4) (subjective norms), 0.3 and 5.9 (1.1) (perceived behavioural control) and 0.6 and 5.4 (1.0) (perception of influence of HPV vaccine on sexual behaviour).
Of the 1381 respondents with male children, 67.8% (95% CI 65.3 to 70.3) intend to vaccinate their son(s) against HPV. In this same study, 73.8% (95%CI: 71.9, 75.7) of parents intend to vaccinate their daughter(s) against HPV. Across different regions in Canada, intention to have sons receive the HPV vaccine ranged from a low of 61.7% in the western most province of British Columbia to a high of 79.8% in the eastern most region of Atlantic Canada (table 2). In bivariate analysis, intention to vaccinate was associated with the region of resident of respondent, gender of respondent, education level of respondent, number of children, household composition, receipt of childhood vaccines, knowledge of HPV and HPV transmission, knowledge of an individual with cancer, being aboriginal, awareness of HPV, the belief that someone was likely to get cervical cancer, attitudes toward vaccines in general, subjective norms and the perceived influence of the vaccine on sexual behaviour (table 3). Having a female sibling, religious affiliation and role of religious beliefs in daily life decisions were not associated with an intention to vaccinate in bivariate analyses. In addition to variables significant in bivariate analyses, role of religion in daily life was included in multivariable modelling, given perceptions that this variable would have an important role in HPV vaccine decision making.26 27 In multivariable modelling, parents who had positive attitudes toward vaccines and the HPV vaccine in particular, parents who were influenced by subjective norms, parents who felt that the vaccine had limited influence on sexual behaviour, parents with more than one child and parents who were aware of HPV were positively associated with intention to vaccinate boys against HPV. In contrast, residence in British Columbia and higher educational status were negatively associated with intention to vaccinate (table 3). Religious affiliation strongly held religious beliefs, cultural background and having a female sibling were not significantly associated with intention to have son undergo HPV vaccination. However, parents who reported an intention to vaccinate their daughters were also highly likely to report an intention to vaccinate their sons (κ = 0.9, p<0.001).
In this study, the majority of parents intend to have their male children undergo HPV vaccination in the context of a publicly funded, Grade 6 (age 11/12 years old) school-based HPV vaccine programme. Parents report a lower intention to vaccinate their sons with the HPV vaccine compared to that of girls.11 In this study, when we discussed the HPV vaccine with study participants, we focused on the benefits of the vaccine as it pertained to cervical cancer and prevention of HPV transmission and so parents may have considered it to be less beneficial for their male children to receive the vaccine. In contrast, parents may be more willing to consider the HPV vaccine if there was greater clarity on the clinical benefits of the vaccine for their sons, including prevention of genital warts and other HPV associated cancers.
The most important predictor of parental intention to have their sons receive the HPV vaccine was overall attitude to vaccines. Parents who felt, in general, that vaccines were beneficial were highly likely to have their son undergo HPV vaccination. Parents also valued the opinion of healthcare professionals (physicians in particular) and other highly regarded community members, including teachers and friends, in making their decision to vaccinate their sons. In addition, parents were concerned about the impact of the vaccine on sexual practices and parents who believed that the HPV vaccine would not promote risky sexual behaviours, including earlier sexual debut or number of sexual partners, were significantly more likely to intend to vaccinate their son(s). To assure uptake of HPV vaccine in young men, parents will require education around vaccine safety and benefit, and there will also be the need to address the belief that the vaccine will promote risky sexual behaviours. Parents with less education were more likely to intend to have their son undergo HPV vaccination. Less educated parents are likely more willing to trust the opinions of health professionals and may feel more comfortable relying on the opinion of government bodies in health policy recommendations than more educated parents. In contrast, other characteristics that might be expected to influence the decision to have sons receive the HPV vaccine, including religious or cultural background, did not emerge in the multivariable modelling as predictive of an intention to have son receive the HPV vaccine.
In this study, we found that intention to vaccinate son varies by region and this variation is consistent with the variation in rates for vaccinating daughters with the HPV vaccine.11 Regional variation in vaccine uptake is not uncommon, although British Columbia reports similar childhood vaccine uptake rates to the rest of the Canadian provinces. Further examination is needed to understand more fully the underpinning of regional variations in intention to vaccinate children, and to determine if this reported intention is consistent with actual uptake rates.
Data on the clinical efficacy of the HPV vaccine for prevention of anogenital warts, anal HPV lesions and HPV-related genital and non-genital cancers is still pending and, given experience with the herpes simplex virus vaccine,28 it is important not to extrapolate clinical efficacy findings from females. However, should the HPV vaccine prove to be efficacious in males, at a population level, mathematical modelling studies have demonstrated that the use of the HPV vaccine in men will offer a significant contribution towards reducing anogenital warts and to cervical cancer, albeit to a lesser degree.29 Policy regarding publicly funded HPV vaccine programmes for males likely requires continued consideration. However, this study confirms that should a school-based programme be made available for boys, the majority of parents would be willing to have their sons undergo vaccination.
This study does possess some limitations. Random digit dialling methods can result in over recruitment of more educated individuals and under recruitment of rural and remote regions. As well, our response rate was less than 60% but, given the large sample size, was unlikely to represent a real threat to validity. In addition, the internal consistency of the scale item for perceived behavioural control was poor (α = 0.3). However, this scale was not significant in the multivariable modelling. In contrast, the scales that were highly significant in the multivariable modelling were also highly internally consistent. However, our previous study employed this same methodology, examined parental intentions to have daughters receive the HPV vaccine11 and had findings that were highly consistent with other international literature. This indicates that our findings as they relate to young men are likely to be highly robust.
In Canada, publicly funded, school-based immunisation programmes for adolescent vaccines have achieved good vaccine uptake in this sometimes hard to reach age group. Uptake rates of hepatitis B vaccine for 12 year olds of both genders in British Columbia are over 85%.30 Over the past year, the federal government offered funding for HPV vaccine programmes, and several provincial governments across Canada have already implemented HPV vaccine programmes for girls.31 32 Should the HPV vaccine be licensed for boys and men, this study shows that, in the context of a school-based vaccine programme, the majority of Canadian parents would intend to have their male children receive the HPV vaccine.
The majority of Canadian parents would have their male children receive the human papillomavirus (HPV) vaccine in the context of a publicly funded school-based immunisation programme.
Intention to have a male child receive the HPV vaccine is highly correlated with intention to have a female child receive the HPV vaccine.
Overall attitudes toward vaccines, recommendations from health professionals and impact of the vaccine on sexual practices are important predictors of parental intention to have a male child receive the HPV vaccine
Funding: Funding for this study was provided by the Public Health Agency of Canada and the BC Centre for Disease Control.
Competing interests: None.
Ethics approval: The study received ethical approval from University of British Columbia.
Contributors: The study was conceived by all of the authors. Study design was led by GO and VR, with assistance from the other authors. GO and VR supervised the study and conducted the data analysis. The manuscript was prepared by GO with assistance from VR. All of the authors revised the manuscript and approved the final version of the submitted for publication.
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