Human papillomavirus (HPV) is a common sexually transmitted infection that constitutes a substantial global healthcare burden. It is associated with genital warts and various cancers (eg, cervical, penile, anal, oropharyngeal, and head and neck cancers). Human papillomavirus causes 4.5% (630 000) of all new cancer cases worldwide.1

In Hong Kong, cervical cancer is the ninth most common cancer, with a crude incidence of 12.9 per 100 000 women and girls.2 3 There are limited data regarding HPV infection or HPV-associated cancers in men and boys. A local study estimated that the incidence of genital warts in Hong Kong was 203.7 per 100 000 person-years. Men and boys had a higher incidence compared with women and girls (292.2 per 100 000 person-years vs 124.9 per 100 000 person-years, respectively), suggesting a similar or possibly higher prevalence of HPV infection in men and boys.4

Human papillomavirus vaccination is a highly effective preventive measure against HPV infection and its complications. National HPV vaccination programmes targeting adolescent girls have significantly reduced the incidences of HPV-associated diseases.5 The World Health Organization recommends including HPV vaccination in routine programmes for girls aged 9 to 14 years, with possible extension to boys if feasible.6

Universal HPV vaccination programmes, covering both adolescent boys and adolescent girls, have become increasingly common in recent years, particularly in developed countries such as the United States, Canada, Australia, and 20 European nations. Female-only vaccination programmes with high vaccine coverage rates have demonstrated substantial public health impact concerning several HPV-related diseases and cancers.7 Gender-neutral vaccination programmes, targeting both boys and girls, have shown greater resilience8 and faster elimination of cervical cancer9; they also provide direct protection to reduce disease burden in all men and in subpopulations of men (eg, men who have sex with men and men who have sex abroad).10 11 12 The achievement of an 80% vaccination rate in both sexes is expected to enable the elimination of HPV subtypes 6, 11, 16, and 18.13

Despite the benefits of a high vaccination rate, the current rate of HPV vaccine is much lower than desired. In Hong Kong, the rate of vaccine uptake reportedly ranged from 2.2% to 7.2% in adolescent girls and 0.6% in adolescent boys before the HPV vaccine was incorporated into the Hong Kong Childhood Immunisation Programme (HKCIP).14 15 16 The 9-valent HPV vaccine was introduced into the Programme for Primary 5 and 6 girls, with a reported first-dose uptake rate of 85% among Primary 5 girls in 2020.17 However, vaccination rates are expected to remain low among adolescent boys.

Prior to the inclusion of HPV vaccination in the HKCIP, few local studies explored parental decision-making14 15 16 18; those that did primarily focused on girls, with limited examination of factors influencing vaccine acceptance or uptake. One survey did include parents of adolescent boys but was hindered by its small sample size (162 boys’ parents).14 Considering the recent implementation of the HPV vaccination programme for primary school girls and the lack of sufficient data concerning HPV vaccination in Hong Kong, further local research is warranted. An understanding of parental acceptance, particularly for boys, can inform strategies to improve vaccine uptake.

This study aimed to identify factors affecting HPV vaccination acceptance among Hong Kong parents of Primary 4 to 6 students. It compared the knowledge, attitudes, and acceptance between girls’ parents and boys’ parents, then explored the underlying reasons for their vaccination decisions.

This cross-sectional survey was conducted from December 2021 to February 2022. Invitation letters were sent to 554 primary schools in Hong Kong, including public local schools, private local schools, and Direct Subsidy Scheme schools. In total, 65 schools agreed to participate. After consent had been obtained from participating schools, parents of Primary 4 to 6 students at those schools received a self-administered online survey through the Qualtrics platform.

The survey was divided into four sections, namely, (1) socio-demographic characteristics, (2) awareness and knowledge regarding HPV and HPV vaccination, (3) attitudes towards HPV vaccination, and (4) acceptance of HPV vaccination. The questionnaires were available in both English and Chinese (online supplementary Appendices 1 and 2, respectively). A detailed description of the survey sections is provided in online supplementary Appendix 3. Upon completion of the online survey, the results were stored in the Qualtrics platform for further analysis.

Human papillomavirus vaccination attitudes were measured using a five-point Likert scale. Two statements (Questions 41 and 42) with strong internal consistency (Cronbach’s alpha=0.81) were combined to form the variable ‘Worried about HPV infection’, and the mean score of the two statements was used for analysis. Similarly, two other statements (Questions 46 and 47) with strong internal consistency (Cronbach’s alpha=0.91) were merged into the variable ‘Worried that HPV vaccine might negatively impact child’s sexual activity’.

Descriptive statistics were used to characterise the participants and study variables. The first analysis compared the knowledge, attitudes, and acceptance of the HPV vaccine between boys’ parents and girls’ parents. Significant differences between groups were identified using the Chi squared test for nominal variables, the t test for continuous variables, and the Mann-Whitney U test for ordinal variables (age-group, household income, and education level). In the second analysis, we investigated factors associated with the acceptance of HPV vaccination for children. Participants whose children had already received HPV vaccination were excluded from the analysis due to missing values in some variables (Questions 49 to 51). Univariate logistic regression was used to estimate the crude odds ratio (OR) and 95% confidence interval (CI). The study variables were included as independent predictors; the acceptance of HPV vaccination for children was regarded as a binary dependent variable (‘Yes’ or ‘No’). Variables with P values <0.1 were entered into multivariate logistic regression. P values <0.05 were considered statistically significant.

Because free HPV vaccination was only provided for primary school girls in Hong Kong, we assumed that factors affecting the acceptance of HPV vaccination for their child varied between boys’ parents and girls’ parents. Consequently, the second analysis was conducted separately for each parent group.

All analyses were conducted using R software (version 4.1.1).

In total, 844 participants completed the survey. Of these, 43.8% were parents of boys and 56.2% were parents of girls. The socio-demographic characteristics of the parents are presented in Table 1.

The HPV vaccine uptake rate is low with boys’ parents reported 6.8% and girls’ parents reported 4.9%. Among children who have received HPV vaccine, >90% of parents in both groups reported that their children received the HPV vaccine through the HKCIP (Table 1).

Awareness of HPV was similar between boys’ parents and girls’ parents (81.4% vs 78.5%; P=0.346). Knowledge scores regarding HPV and the HPV vaccine were low in both parent groups; parents of boys had higher mean scores compared with parents of girls (6.48 vs 6.03; P=0.012). More boys’ parents discussed sexually transmitted disease (STDs) with their children, relative to girls’ parents (33.0% vs 15.2%; P<0.001) [Table 2].

Two questions addressed the timing of vaccination, namely: ‘At what age should a child receive the HPV vaccine?’, and the yes/no statement ‘I believe it’s better for my child to receive the HPV vaccine before they become sexually active’. A majority of parents, both of boys (83.6%) and of girls (85.9%), believed that their children should receive the HPV vaccine at age ≥13 years. Additionally, more parents of boys (55.7%) believed that their children should receive the HPV vaccine before becoming sexually active; more parents of girls (51.1%) reported a neutral perspective on this statement. Regarding HPV infection and HPV vaccine effectiveness, parents in both groups were worried about HPV infection (mean±standard deviation [SD] out of 5: 3.56±0.74 in boys’ parents; 3.48±0.76 in girls’ parents). Over 70% in parents of both groups believe that their children cannot be protected from HPV without HPV vaccination, furthermore a majority of parents in both groups also believe in the vaccine’s effectiveness (90.2% in boys’ parents and 84.6% in girls’ parents) [Table 2].

Concerning vaccine safety, impacts, and cost, most parents of boys (90.8%) and parents of girls (84.8%) agreed that the HPV vaccine is safe. They had a neutral perspective or were less worried about the vaccine’s short-term (62.5% and 67.6%, respectively) and long-term side-effects (80.5% and 82.3%, respectively) [Table 2].

Additionally, parents had a neutral perspective or were less worried about the vaccine’s negative impacts or influence on adolescent development. However, most parents agreed that the HPV vaccine is too expensive (88.1% and 79.8%, respectively) [Table 2].

We observed high acceptance of the HPV vaccine for their children in boys’ parents (73.8%) and girls’ parents (89.7%). If the HPV vaccine were subsidised under the HKCIP, acceptance in parents would slightly increase because the government would cover the cost (78.9% and 92.6%, respectively) [Table 2].

The reasons for accepting the HPV vaccine for their children were similar between parent groups (Fig), with a majority citing concerns about HPV infection (91.0% in boys’ parents and 78.6% in girls’ parents). Acceptance was least influenced by religions and culture (<3%) or advertisements (<5%) in parents of both sexes. The reasons for declining the HPV vaccine for their children were somewhat different between boys’ parents and girls’ parents. ‘The HPV vaccine is too expensive’ was the top reason chosen by both boys’ parents (46.4%) and girls’ parents (42.9%). The other two reasons most often selected by boys’ parents were ‘Not enough information about the HPV vaccine provided to me’ (32.0%) and ‘My child doesn’t like vaccinations’ (22.7%). For girls’ parents, the other two reasons were ‘My child doesn’t like vaccinations’ (38.8%) and ‘The HPV vaccine can cause adverse effects/is not safe’ (36.2%) [online supplementary Fig].

The association analysis excluded 25 parents of boys and 23 parents of girls whose children had already received the HPV vaccine. The acceptance rates of the HPV vaccine for children of boys’ parents and girls’ parents, stratified according to the study variables, are listed in online supplementary Tables 1 and 2, respectively.

Regarding boys’ parents, 24 study variables with P values <0.1 in univariate logistic regression were entered into multivariate logistic regression (Table 3). Factors associated with higher acceptance of the HPV vaccine for children included parental receipt of the HPV vaccine (OR=9.36, 95% CI=1.5-63.82; P=0.018), knowledge of the HPV vaccine (OR=10.16, 95% CI=3.02-39.07; P<0.001), and stronger beliefs that ‘it’s better for my child to receive the HPV vaccine before they become sexually active’ (OR=3.27, 95% CI=1.66-7.09; P=0.001) and ‘I am worried that the HPV vaccine might affect adolescent development’ (OR=2.56, 95% CI=1.39-5.03; P=0.004). Conversely, factors associated with lower acceptance of the HPV vaccine were the presence (in the respondents’ families) of more children in Primary 4 to Primary 6 (OR=0.28, 95% CI=0.12-0.63; P=0.002), a history of discussing STD prevention with their children (OR=0.23, 95% CI=0.08-0.64; P=0.005), receipt of regular seasonal influenza vaccines (OR=0.15, 95% CI=0.04-0.48; P=0.002), child’s receipt of regular seasonal influenza vaccines (OR=0.25, 95% CI=0.08-0.80; P=0.021), and stronger beliefs that ‘my child can be protected from HPV without HPV vaccination’ (OR=0.28, 95% CI=0.11-0.66; P=0.005) [Table 3].

Regarding girls’ parents, 19 study variables were entered into multivariate logistic regression. Higher acceptance of the HPV vaccine for their children was associated with higher monthly household income (OR=4.3, 95% CI=1.95-10.47; P=0.001) and the combined variable ‘worried about HPV infection’ (OR=2.39, 95% CI=1.08-5.73; P=0.038). Older age-group (OR=0.38, 95% CI=0.17-0.82; P=0.018) was the only variable associated with lower acceptance of the HPV vaccine (Table 4).

This survey of 844 Hong Kong parents (370 boys’ parents and 474 girls’ parents) revealed high HPV vaccine awareness but relatively low knowledge of HPV and the HPV vaccine. Parents believed the vaccine was safe and effective in preventing HPV infection. Acceptance of the HPV vaccine was lower among boys’ parents than among girls’ parents, and factors associated with acceptance differed between the two parent groups. Differences in socio-demographic characteristics were observed, such that more boys’ parents discussed STDs with their children and had experience with regular seasonal influenza vaccines, the HPV vaccine, and Pap smears.

Although a majority of parents of both sexes had knowledge of the HPV vaccine, their average scores indicated a low overall understanding of HPV and HPV vaccination. This finding is consistent with the results of previous studies, which showed that general knowledge and awareness of HPV among parents in Hong Kong remain low despite some improvement over time.14 15 16 18 19 20 Considering the substantial healthcare burden associated with HPV-related diseases in Hong Kong, there is an urgent need for educational or promotional programmes to enhance vaccine acceptance and uptake.

In our study, parents expressed concern about HPV infection and strongly favoured HPV vaccination for their children before the children became sexually active. These beliefs support educational and promotional campaigns targeting the early adolescent age-group.

The reported HPV vaccine uptake rate is low in both groups (6.8% in boys and 4.9% in girls). The low vaccine uptake rate reported in girls is particularly alarming considering the recent inclusion of the HPV vaccine in the HKCIP and the high vaccination rate of 85% reported in the 2019/2020 school year.17 Among those parents who reported their children of receiving the HPV vaccine, >90% of them, including boys’ parents, indicated that their children received the vaccine through the HKCIP. This finding provides evidence suggesting insufficient public health campaigns, resulting in a lack of knowledge among parents on the HPV vaccination programme and the HKCIP, subsequently leading to potential confusion among parents.

Notably, girls’ parents in our study reported a belief that the HPV vaccine is too expensive, despite the availability of free HPV vaccination through the HKCIP. This finding again reinforces a potential lack of awareness regarding the Programme, possibly due to inadequate dissemination of information during the coronavirus disease 2019 pandemic. Similar trends have been observed in other Western countries, where routine vaccinations (including HPV vaccination) were disrupted by the pandemic.21 22 Catch-up vaccination services for affected children should be implemented promptly to prevent future healthcare burdens.23 24 25 26

This study examined the factors influencing parental acceptance of HPV vaccination for boys and girls. Parents who had more children in Primary 4 to 6 were less likely to accept the vaccine, possibly due to cost concerns. Discussions with children about STD prevention and previous receipt of seasonal flu vaccines did not lead to higher acceptance rates. These findings imply that vaccination is not a common topic in STD prevention campaigns, a point that warrants attention in future educational efforts focused on STD prevention. Intriguingly, parents with greater concern that the HPV vaccine affects adolescent development were more likely to accept it; they also had higher knowledge and awareness of HPV (online supplementary Table 3). This result highlights the need to increase parental understanding of HPV and the HPV vaccine, including efforts to clarify potential misconceptions and mitigate safety concerns.

Our data indicate that parental concerns about HPV infection strongly influence vaccine acceptance, whereas concerns about genital warts and HPV-related cancers are less impactful. This discrepancy may be attributed to an optimistic bias, where parents associate HPV complications with promiscuity and believe that their children have low STD risk.18

Notably, parents ranked HPV vaccine recommendations from healthcare professionals, relatives and friends, and schools as more important reasons to accept the vaccine, compared with recommendations by health authorities. This result may suggest that government initiatives provide suboptimal education concerning HPV and the HPV vaccine.

Barriers to HPV vaccine acceptance include costs and children’s preferences, which may explain the discrepancies between uptake and acceptance. Cost is a well-established barrier to vaccination uptake. However, we note that the vaccine is free for girls in our study population, which highlights the importance of awareness. Health messages to boys’ parents should emphasise the value of HPV vaccination as a long-term investment in their sons’ health.14 Concerns about vaccine safety and adverse effects, as well as a lack of recommendations from healthcare professionals or a lack of general knowledge, may also hinder vaccine acceptance.

We found that parental knowledge of HPV and the HPV vaccine significantly influenced decision-making in boys’ parents, indicating that educational campaigns targeting HPV acceptance may be more effective for these parents than for girls’ parents. This difference might be partly related to the feminisation of HPV, especially in Hong Kong. This phenomenon has been observed in a regional qualitative study focusing on men’s perceptions of HPV and HPV vaccination.27 Because the Chinese translation of the HPV vaccine is ‘cervical cancer vaccine’, many boys and men in Hong Kong perceive a low risk of HPV infection.27 28 29 In this context, campaigns or strategies using a fear-based approach to increase the perceived risk of HPV infection may be more effective for boys’ parents.

This study had several limitations. First, it was a cross-sectional study and thus provided less robust evidence than would be obtained in a longitudinal study. Vaccine acceptance is merely an indicator of potential uptake, and it is unclear whether this acceptance will be translated into action. Second, this study relied on parents to self-report their outcomes, and it lacked the ability to verify information provided by participants. Third, the results may have been influenced by volunteer bias or other selection biases. Because the survey was self-administered, random sampling of the general study population could not be achieved due to intrinsic differences between those who did and did not choose to participate. Volunteer bias may explain the variation in baseline characteristics between boys’ parents and girls’ parents. This bias limits the generalisability of the study results to the broader population. Fourth, the use of previously validated scales or items was limited. Previous studies were used as a reference to construct the survey questionnaire, but questions were not directly adapted. Although such validated measures exist, due to the lack of research regarding HPV and HPV vaccination, no measures have been validated in Hong Kong.30 31

One possible future research direction involves conducting longitudinal studies to examine the factors affecting vaccine uptake. These studies can produce stronger evidence and more effectively inform strategies for improved vaccine uptake. Furthermore, because this study only screened for variables involved in parental decision-making, a more thorough investigation could be done to better understand this process. Qualitative studies (eg, involving focus groups or interviews) can provide a more in-depth understanding of parents’ attitudes, perceptions, and decision-making processes regarding HPV vaccination acceptance.

This study represents the most extensive local investigation into factors affecting parental acceptance of HPV vaccination in Hong Kong after the implementation of a school-based outreach programme. We found that high awareness of HPV and the HPV vaccine is predictive of vaccine acceptance. To increase vaccination rates among adolescents, we recommend targeted interventions based on the identified factors, including public education for parents and children to raise awareness of HPV risks, the benefits of vaccination for boys, and STD prevention. We also suggest including HPV vaccination for boys in the HKCIP and implementing catch-up vaccination for affected children. Extension of the catch-up programme to school children beyond Primary 6 should be considered to maintain high vaccination rates.

All authors (except for PH Wong and EYT So) contributed to the concept or design of the study, acquisition of the data, analysis or interpretation of the data, drafting of the manuscript, and critical revision of the manuscript for important intellectual content. PH Wong and EYT So contributed to the concept and design of the study questionnaire. All authors had full access to the data, contributed to the study, approved the final version for publication, and take responsibility for its accuracy and integrity.

PH Wong and EYT So are employees of Merck Sharp and Dohme (Asia) Ltd. Other authors have disclosed no conflicts of interest.

The authors thank Dr Ka-yu Tse from the Division of Gynaecology Oncology of the Department of Obstetrics and Gynaecology of The University of Hong Kong for review of survey questions.

This research was sponsored by Merck Sharp & Dohme LLC, a subsidiary of Merck & Co, Inc (Rahway [NJ], United States) [Ref No.: NIS009837]. The sponsor had no role in collection, analysis, or interpretation of the data, nor did it participate in manuscript preparation.

This study was approved by the Institutional Review Board of The University of Hong Kong/Hospital Authority Hong Kong West Cluster, Hong Kong (Ref No.: UW21-574). Participants provided informed consent via the online survey platform before survey completion.

The supplementary material was provided by the authors and some information may not have been peer reviewed. Accepted supplementary material will be published as submitted by the authors, without any editing or formatting. Any opinions or recommendations discussed are solely those of the author(s) and are not endorsed by the Hong Kong Academy of Medicine and the Hong Kong Medical Association. The Hong Kong Academy of Medicine and the Hong Kong Medical Association disclaim all liability and responsibility arising from any reliance placed on the content.

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