Determinants of vaccination against HPV

Much attention has been devoted to determinants influencing HPV vaccine uptake. Most studies have found that the perceived benefits of the vaccine have considerable effects on decisions about whether to vaccinate; the intention to vaccinate increases with the perceived benefits. Commonly reported benefits involve the perceived effectiveness of the vaccine [9–11] and beliefs that the vaccine will protect against or minimize the severity of HPV-related disease and/or promote the future health of recipients and their future partners and others in the community through herd immunity [9, 10, 12–14].

Perceived barriers also influence decisions about whether to vaccinate against HPV. Reported barriers entail the low perceived effectiveness of the vaccine, concerns about side effects and safety, fear of needles, fear of sexual disinhibition or promiscuity stigma, and lack of knowledge and awareness [9, 10, 14–18]. The latter involve misconceptions regarding the physical injection site [12] and the prophylactic effect of the vaccine [12, 19]. In addition, there is low awareness of the existence of HPV vaccination for men, as the vaccine has been advertised mainly for women. Thus, men have not adopted HPV immunization as a norm [20], potentially emasculating those who decide to be vaccinated [17]. Other barriers, such as lack of trust in the government (promoting the vaccine) and/or concerns about commercial interests of pharmaceutical companies, have also been reported to compromise HPV vaccine uptake [9, 10, 14, 15].

Another important determinant affecting decisions about whether to vaccinate is the perceived severity of HPV and perceived susceptibility to HPV-related diseases; most studies have shown that beliefs about the severity and likelihood of HPV infection and/or development of HPV-related diseases positively affect vaccination uptake [13–15, 20–22]. However, many girls perceive a low likelihood of contracting HPV, perhaps due to the young vaccination age [9, 10]. Studies have also suggested that anticipated regret of (in)action plays an important role in HPV vaccination decisions [12, 13, 23, 24]. Furthermore, general acceptance of other childhood vaccinations and professional endorsement have been shown to affect HPV vaccine acceptance [14, 15, 17, 25].

In addition to all of these beliefs, demographic determinants (e.g., education, religion), social influences, and subjective norms (e.g., peer acceptance) have been found to affect the decision to vaccinate [10, 21, 25–27]. Finally, demographic characteristics such as education level have been reported to have less influence than the above-mentioned belief factors on vaccination acceptance [21, 28].

Statement set development

To develop a comprehensive and structured set of statements, including all beliefs and motives potentially affecting decisions to vaccinate against HPV, we used the health belief model (HBM) as the theoretical framework for this study. The HBM can help to explain and predict health behaviours [31]. It has proven relevance in various fields of preventive care, including HPV vaccination behaviour [32, 33]. Hence, we used HBM as reference for selecting a set of statements covering the variety of beliefs and motives relevant to our study. The HBM has five major components shaping individuals’ health beliefs: perceived severity (seriousness of a disease), perceived susceptibility (likelihood of getting a disease), perceived barriers (tangible and psychological costs of the action), perceived benefits (advantages gained from the action), and self-efficacy (belief in one’s ability to execute a behaviour) [35]. Perceived severity and susceptibility have been described as “perceived threat,” which provides the strength and power to act, whereas assessment of the potential benefits and barriers defines the preferred path of action [34]. To accept or follow a preventive action, optimal beliefs about susceptibility and severity are sufficient only when the perceived benefits outweigh the perceived barriers, reducing the perceived threat [34, 35]. Self-efficacy also affects individuals’ health beliefs [34]. In addition to these five major components, an action is further influenced by internal and external “cues to action” (e.g., symptoms, media) and “modifying factors” (e.g., age, education, ethnicity) (34). We added a “social influences” component, involving subjective norms (e.g., beliefs about whether significant others think that one should engage in a behaviour) to the model, based on findings that the social environment and subjective norms (e.g., peer acceptance) are important influences on HPV vaccination decisions [10, 21, 25–27]. Although some researchers consider this factor to be part of the “cues to action” component, others have used it as an additional component in an extended HBM [36, 37]. Figure 1 depicts the adapted version of the HBM used in this study, which is based on Champion and Skinner [34].

Through a non-systematic review of scientific, empirical, and popular literature, two researchers (NP, JC) independently identified a large variety of motives and beliefs potentially influencing decisions to vaccinate against HPV among girls, boys, and parents. The scientific literature was searched using PubMed. In addition, interviews were conducted with two experts in the field of HPV vaccination from two academic medical centres in the Netherlands (one specializing in obstetrics and gynaecology and the other in obstetrics, gynaecology, immunology, and oncology). The two researchers divided the identified motives and beliefs according to the components of the extended HBM, and then reviewed the literature a second time to ensure that nothing had been overlooked.

Four researchers (NP, HD, JE, JC) developed an initial set of 48 statements, and the two experts were asked to evaluate its exhaustiveness. Following their feedback, minor adjustments were made; some statements were merged or deleted because they covered similar topics, and the wording of several statements was revised. Thereafter, two additional HPV policy experts (IW, RB) provided feedback on the statement set, leading to further reduction of the number of statements and additional adjustments to language use. This iterative process resulted in a draft set of 35 statements.

Data collection

An external agency recruited participants purposively to achieve demographic and cultural diversity in terms of age, gender, education level, religion, and ethnicity. In addition, the following inclusion criteria were applied: girls and boys aged 10–16 years who had not yet received HPV vaccination, and parents or legal guardians of such children. Participating parents and children did not have to be from the same families. Initially, three sessions were planned in each of three locations in the Netherlands (Amsterdam, Amersfoort, and Rotterdam). Because 16 participants did not show up, an additional session was organized in Rotterdam. Each session was attended by 6–15 participants. All respondents received €25 gift cards and reimbursement for travel expenses.

Each session (moderators: NP, HD) was organized in the following manner: parents and children were separated into different rooms and received a short introduction on HPV (Appendix 1), which provided limited information to minimize potential influence. Participants received written instructions for the exercise. Because these instructions appeared to be too difficult for children in the first session, we switched to verbal instructions for all sessions with children. Thereafter, each respondent was presented with the 35 statements printed on cards, in random order, and asked to carefully read all cards and sort them into three piles representing statements they agreed with, disagreed with, and found to be neutral or irrelevant. The participants were then instructed to reread the cards in each pile, prior to ranking them on the score sheet (Fig. 2). Respondents first placed statements with which they agreed on the right side of the score sheet. They placed the two statements with which they agreed most in the two spots in the far right column, followed by the three remaining statements with which they agreed most, and so on. In the same manner, respondents ranked statements with which they disagreed and those that they found to be neutral on the left side and in the centre of the score sheet, respectively.

After ranking the statements, each participant was asked three open-ended questions. They were asked to elaborate on their choices of the two statements with which they most agreed and disagreed, and to briefly describe their opinion about HPV vaccination. Finally, participants were asked to fill in a questionnaire, which included questions regarding demographic characteristics, knowledge about HPV, HPV vaccination, and their intended vaccination decision.

After data analysis, interviews were conducted with eight participants showing the highest correlations with the identified perspectives (i.e., two participants per perspective). These ex-post interviews were transcribed verbatim.

Analysis

Individual statement rankings were subject to by-person factor analysis (i.e., centroid factor extraction, followed by varimax rotation) using PQMethod 2.11 [38]. Identified factors were interpreted as perspectives on HPV vaccination using the composite statement rankings. Consensus statements (i.e., those whose rankings did not differ significantly between any pair of factors) and distinguishing statements (i.e., those whose rankings in one factor differed significantly from those in all other factors) were identified. Next, the interpretation and description of each factor was supplemented with the answers to the open-ended questions from participants whose rankings were associated with that perspective (p < .05). Finally, ex-post interview data were used to verify and/or clarify interpretations of the factors. Two respondents with the highest factor loadings (i.e. correlations between the respondent and the factors) were selected per factor for the ex-post interviews, as those respondents can be seen as holding the most similar perspective to the one represented by the factor. Two respondents per factor was considered sufficient to verify and clarify interpretations, as no new themes emerged after these interviews.

Perspective 1: “Prevention is better than cure”

This pro-vaccination perspective, with which 45 participants [35 (78%) parents, 1 (2%) girl, 9 (20%) boys] were associated significantly, emphasized the perceived threat of HPV and HPV-related diseases. An urgency to take preventive measures against HPV prevailed, as reflected in the rankings of statements describing the perceived severity of and susceptibility to HPV and HPV-related diseases. Participants with this perspective believed that they were likely to be exposed to HPV infection (statement 14 was ranked −1), were concerned about its potential consequences to their health (st.13,+1; st.18,+3), and placed importance on prevention through vaccination (st.17,-3).

From this perspective, the benefits of HPV vaccination clearly outweighed potential barriers. Vaccination was considered to be a positive means of preventive care to protect oneself and others (st.21,+4), with more advantages than disadvantages (st.20,-1), giving people the direct ability to influence their health (st.1,+3). Taking preventive measures was seen as a small sacrifice relative to the potential consequences of HPV-related diseases, as highlighted in several answers to open-ended questions with the recurring idiom of “prevention is better than cure.”

Another theme that emerged within this viewpoint was the perceived complexity of HPV and HPV-related diseases, reflected in beliefs about who should make the vaccination decision [i.e., not children alone (st.31,-3) or parents and children together (st.30,+1)]. Parents stated that they would rather announce this decision to their children than negotiate it with them. They felt strongly that children receiving formal invitation letters for local vaccination sessions could not understand such complex information and were incapable of making informed decisions.

Given the perceived complexity of the topic, participants with this perspective valued professional advice from trusted sources, such as governmental recommendations (st.28,+3). This perception may explain the minimal value placed on social influences (st.33,-1; st.34,-3; st.8,0): one mother said, “I do not rely on the opinion of my neighbor or sister-in-law; I collect good information from the Internet about pros and cons and then make my choice.” These participants’ trusting relationships with the government may additionally explain their generally favorable opinion of HPV vaccination. In ex-post interviews, respondents opined that the government would not add a vaccine to the NIP without proper and relevant justification. In the context of healthcare and the “medical world” in the Netherlands, participants with this perspective trusted the government to make good, wise choices with people’s best interests in mind.

Perspective 2: “Fear of unknown side effects”

This perspective, with which 46 participants [40 (87%) parents, 4 (9%) girls, 2 (4%) boys] were associated significantly, did not involve the strength and force to take action against HPV through vaccination, as the perceived severity and susceptibility of HPV-related disease was minimal. The perceived likelihood of exposure to HPV-related disease was minimal (st.14,+1) and concern about contracting HPV-related disease was negligible (st.13,-1). Hence, respondents with this perspective did not perceive HPV to be sufficiently important to warrant vaccination (st.17,-1).

Perceived barriers, particularly fear about the potential unknown long-term side effects of HPV vaccination (st.10,+4; st.27,-4), dominated this perspective. In this way, HPV vaccination was distinct from other childhood vaccinations (st.23,-3). One mother stated, “[I have] concerns about the side effects in the long term. The vaccine was developed only recently. The possible long-term side effects cannot be known yet.” Respondents also referred to the effectiveness of the vaccine, emphasizing that the current vaccine does not protect against all cancer-causing HPV strains. One interviewee also questioned the duration of the vaccine’s protection against HPV infection.

Respondents’ fears were also linked to mistrust of pharmaceutical companies, perceived as profit-making entities that wanted to sell their products, even at the cost of others’ well-being (st.29,+3). Participating mothers stated, “Ah yes, surely they make plenty of money with it. Without really telling the truth about the severe side effects” and “This is nothing new. The pharmaceutical companies often are big crooks with dollar signs in their eyes. The humane element in the pharmaceutical industry has gone, regrettably.” This mistrust of the pharmaceutical industry and the prevailing fear about potential negative consequences made respondents perceive children vaccinated against HPV as test objects; one mother said, “I don’t really want my daughter to act as a guinea pig or for people to make money out of her at the cost of her health.” Thus, these participants considered it better to be safe and not get vaccinated, than to regret vaccination due to potential future side effects (st.12,+3). However, they also expressed that only the future could tell whether they had made the right decision.

This perspective also involved a lack of trust in the government to give advice about HPV vaccination (st.28,0). One interviewee referred to the government’s hasty choice to include the HPV vaccine in the NIP. In addition, these respondents placed little value on the role of GPs relative to those with other perspectives (st.2,0).

Participants with this perspective perceived that adequate and objective information on HPV vaccination was difficult to find (st.3,0; st.4,+2), which may partly explain the perception that they were inadequately informed about HPV and related diseases (st.5,-1). In addition, they perceived HPV as a complex topic and thus felt that parents should make vaccination decisions (st.24,+3). One respondent emphasized that her daughter was very compliant, with a constantly altering opinion depending on with whom she had spoken.

Perspective 3: “Lack of information and awareness”

The defining feature of this perspective, with which 38 participants [14 (37%) parents, 14 (37%) girls, 10 (26%) boys] were associated significantly, was lack of awareness and information about HPV and HPV-related disease, which posed a major barrier to informed decision making (st.25,-4; st.6,-4). Many participants stated that the topic of HPV was completely unclear for them, and some had not heard about HPV before this study. Interviewees linked HPV with cervical cancer, albeit diffusely. Given their limited awareness and information, they pondered the advantages and disadvantages of vaccination, being unclear about its potential side effects (st.27,+4) while perceiving the benefits of vaccination in general, and HPV vaccination specifically, as important (st.9,+4; st.21,+3).

This perspective involved the least perceived severity among viewpoints of the potential consequences of HPV-related disease (st.18,0) and a neutral perception of susceptibility (st.14,0; st.13,+1). Yet, interviewees stated that cervical cancer could be severe. This contradictory view could be explained by the expressed lack of information, awareness, and clarity regarding the link between HPV and (cervical) cancer.

Respondents valued friends’ and family members’ opinions about the HPV vaccine (st.33,+1), and thus appeared to be influenced more easily by the social environment. In contrast to participants with other perspectives, those with this viewpoint valued GPs’ advice highly (st.2,+3). A 14-year-old girl said, “I think advice from the GP is important because you don’t know the drawbacks of an HPV shot. There is not enough information about the HPV shot” and a father stated, “Explanation by a GP gives you some more certainty! He is a specialist after all.”

Interviewees wished that they knew more about HPV and HPV-related disease. When asked how information should be distributed, one respondent suggested more active communication about the vaccine through spot advertisements and increasing awareness through GPs and informational pamphlets distributed with formal invitations for other vaccinations.

In addition, many children holding this view appeared to trust and rely on their parents’ decision, but felt that they should have a say in this decision despite their limited knowledge about the HPV vaccine. A 13-year-old girl, who had declined vaccination, stated that she would have liked to know more about HPV before making a decision and expressed anticipated regret if she were to acquire an HPV-related disease later in life. However, she declined having plans to rethink her decision.

Perspective 4: “My body, my choice”

The 22 participants [2 (9%) parents, 15 (68%) girls, 5 (23%) boys], in large majority girls, associated significantly with this perspective did not perceive HPV-related diseases as a particular threat to health. Perceived susceptibility was especially low, as respondents did not seem to worry about exposure to HPV and related diseases compared with those with other perspectives (st.13,−2). One 14-year-old girl stated that she had decided to decline the HPV vaccine, but not other childhood vaccinations: “…these I felt were important and therefore I accepted them.” This viewpoint was further justified by the fact that common childhood vaccinations prevent diseases perceived as more common than HPV-related disease.

Yet, respondents felt clearly that making the decision to vaccinate before becoming sexually active was important (st.16,-3). Although they believed that vaccination in general benefitted oneself and others (st.21,+2), respondents representing this perspective seemed to be undecided about whether HPV vaccination has more disadvantages than advantages (st.20,0). One interviewee referred to unknown side effects, and another referred to the effectiveness of the vaccine, stating she had heard that the vaccine’s ability to protect against cervical cancer was uncertain.

The most important aspect of this viewpoint was control over the decision of whether to vaccinate. Children believed that they should make this decision (st.31,+4), positioning themselves (as vaccine recipients) centrally in responses to open-ended questions and in ex-post interviews; a 15-year-old girl stated, “It’s your body so I think you may take the decision yourself.” Children also expressed that their opinions were equally important as their parents’, if not more important: 14- and 13-year-old girls stated, “Well, they thought my opinion was really important; so I didn’t have to get it if I didn’t want it” and “Yes, [my parents] thought my opinion was more important.”

However, children also valued their parents’ knowledge and saw the decision as joint (st.30,+4): 12- and 14-year-old girls said, “But it may be that as a child you are not too sure about what it involves, so therefore I find it important that parents also have a say in this” and “As a child you don’t know much about this but your parents just a bit more, so it’s useful to have them help decide.”

A probable cause for this rather contradictory view on who should make the decision is that children want to be able to decide who can influence the decision: preferably only people from their “circle of trust” (st.33,-3). Yet, those with this perspective greatly appreciated GPs’ recommendations (st.2,+3); a 13-year-old girl said of her GP, “He knows me,” and referred to GPs’ medical knowledge about their clients. Yet, neither girl with this perspective who was interviewed had actively reached out to her GP for advice, despite having decided to decline the vaccination. Expert advice from other sources, such as the government, was not considered to be relevant (st.28,-2). However, most children did not appear to fully understand the term “government” or what it entailed.

Lack of information did not appear to be a barrier for respondents with this perspective (st.25,+3), even those who expressed that they knew little about HPV and HPV-related disease. Compared with participants with other perspectives, they felt that knowledge, when needed, was easily obtainable from parents or GPs (st.3,+2).