Human papillomavirus (HPV) is the most common sexually transmitted infection (STI) in the United States1-with 20 million Americans currently infected and another 6.2 million people estimated to get newly infected annually. About 50% of sexually active men and women will acquire genital HPV infection at some point in their lives.2

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HPV infection in women has been associated with genital warts as well as cervical, vaginal, and vulvar cancers, whereas HPV infection in men has been associated with genital warts, anal, and penile cancers.2,3 Furthermore, oral HPV infection has also been established as an important cause of head and neck cancers.4

HPV can be divided into high-risk oncogenic types (for example, 16 and 18) and low-risk nononcogenic types (for example, 6 and 11). These high-risk HPV types are responsible for 70% of cervical cancer cases in women and also cause precancers and cancer of the penis and anus. The low-risk HPV types are responsible for 90% of genital warts in both sexes and are also the cause of recurrent respiratory papillomatosis or condylomata of the nasopharynx.3,5,6

There are currently two HPV vaccines marketed internationally, the quadrivalent and bivalent vaccines.7 The FDA approved the quadrivalent vaccine, Gardasil (Merck), in 2006 for use in girls and women ages 9 through 26 years. Gardasil is indicated for the prevention of precancerous lesions, genital warts, and cervical, vulvar, and vaginal cancers in females caused by HPV types 6, 11, 16, and 18.1,7,8 Gardasil, as of October 16, 2009, is also now approved for the prevention of genital warts caused by HPV types 6 and 11 in boys and men ages 9 through 26 years.1 On the same day, the FDA also approved the bivalent HPV vaccine, Cervarix, produced by GlaxoSmithKline (GSK). The bivalent vaccine is indicated for the prevention of cervical precancers and cancers associated with HPV types 16 and 18 in females ages 10 through 25 years.9 As of this writing, Cervarix is not FDA approved for use in males.

It is estimated that about 1 million American men have genital warts caused by HPV and that annually about 2 out of every 1,000 men in the United States are newly diagnosed.1,10 The recent approval of Gardasil vaccination in males is an important step toward reducing the incidence and prevalence of HPV infection in men.

The FDA approval of Gardasil for use in males also has the potential of greatly reducing HPV-associated diseases in women.8 "Herd immunity" occurs when there is a reduction in vaccine-preventable illness through directly protecting those vaccinated as well as the indirect protection of others in the community. Vaccinating men against HPV not only may reduce male HPV-associated disease burden but may also be effective in reducing female HPV-associated disease because men's sexual behavior has been shown to affect women's risk for cervical neoplasia even when controlling for female sexual activity.10 A study that supports this notion of herd immunity conducted by Elbasha, Dasbach, and Insinga11 suggests that vaccinating both sexes may be the most effective strategy for reducing the incidence of genital warts, cervical intraepithelial neoplasia, and cervical cancer as well as reducing HPV-associated healthcare costs compared to vaccinating women alone.

Economic and emotional burden may also be reduced through male HPV vaccination. Infection with HPV has been associated with significant morbidity and substantial healthcare costs. In 2000 alone, direct medical costs associated with HPV infection in 15- to 24-year-old Americans was $2.9 billion.12

Finally, men who have sex with men (MSM) are a unique population who also stand to greatly benefit from HPV vaccination. Studies have demonstrated a high prevalence of HPV infection in MSM along with a high rate of HPV-related anal cancer.3,13

There have been numerous studies on HPV vaccine acceptability among parents, physicians, and women, but few have focused on acceptability of the HPV vaccine among men.8 Brewer and Fazekas14 conducted a systematic review of studies examining HPV-related health beliefs that are likely to influence the decisions of young women and parents of adolescent girls when deciding about HPV vaccination. They found that vaccination was more acceptable when people believed the vaccine was effective, a physician recommended it, and HPV infection was likely. Identifying whether these beliefs are similar or different in males will help recognize points that HPV vaccine programs in the United States should emphasize to increase male vaccine uptake.

The purpose of this literature review is to assess adolescent and adult men's knowledge of HPV, the HPV vaccine, and the benefits of HPV vaccination as well as to determine how this affects their acceptance of the vaccine and intent toward getting vaccinated. It is necessary to study this topic because relevant findings can guide how primary care healthcare professionals, including advanced practice nurses, should frame information regarding the HPV vaccine when recommending it to male patients. This information can also be useful with regard to how media and vaccination campaigns promote the HPV vaccine to increase male acceptability, interest, and intent to get HPV vaccinated.

Methods

A search of the literature was conducted using the search engines PubMed and CINAHL. The limits applied to the PubMed and CINAHL search engines were so that only "male" relevant articles published between 2004 and 2009 were included. Key search terms used were "HPV vaccine" and "papillomavirus vaccine." A third search term "HPV vaccine acceptability" was used with the only limit being that articles published between 2004 and 2009 were included. These searches yielded an initial set of articles (n = 1,098). Criteria for articles included in this literature review were those published in English and those that examined men's knowledge of HPV, the HPV vaccine, and their acceptance, interest, and/or intent to receive the HPV vaccine. Articles that only assessed men's knowledge of HPV were excluded. Studies that incorporated these criteria in both sexes were included due to the limited number of articles that focused on males alone. The search results were compared and the author selected 15 articles based on 14 studies that met the criteria.

Results

Of the 14 studies, one was a randomized controlled trial, six were quasiexperimental studies, three were nonexperimental studies, and four were qualitative studies utilizing either interviews or focus groups. Six studies included only male participants, whereas the other eight studies included both males and females. Of the studies that included both sexes, all had a separate gender analysis. Half of the studies reviewed were conducted before, around the time, or shortly after the HPV vaccine was approved for use in females, and this might have influenced study results as HPV vaccine information may not yet have reached the general public. Of the 14 studies, half were conducted in the United States. Study participants' ages ranged from 15 to 75 years and older with majority of participants being between 18 and 45 years old.

Knowledge of HPV and the HPV vaccine

Current evidence available from studies in countries across the globe including Malaysia, Holland, Sweden, Australia, the United Kingdom, and the United States have shown that men have limited knowledge regarding HPV infection and the HPV vaccine.

Studies conducted in the United States have generally found that although many males may report having heard of HPV, further questioning usually revealed that baseline knowledge regarding HPV infection was low.8,15,16 Several studies also demonstrated that males generally had limited-to-moderate knowledge regarding the availability of an HPV vaccine ranging from 1.1% to 63% of study participants.8,13,15,17,18

Study results were inconsistent as to whether there was a gender difference in knowledge of HPV or of the HPV vaccine. A Swedish study of high school students, a U.K. study of 16- to 54-year-olds, and an Australian study of 14 young men and women between ages 18 and 23 years all found that study participants had extremely limited knowledge regarding HPV and that gender was not a significant factor with respect to HPV knowledge.17,19,20

In contrast, another Swedish study of high school students and a study of Dutch adults found that the males were generally less knowledgeable than females regarding HPV and its health consequences.18,21 A U.S. study also showed that HPV awareness was slightly higher in females than in males across all racial and geographic groups that participated in focus groups.22

Several studies revealed common misconceptions found among participants. A U.S. and Malaysian study that used focus groups found that participants were unaware that HPV infection is fairly common.23,24 Two U.S. studies found that participants demonstrated considerable confusion between genital warts and genital herpes.8,22 Studies also found that many men were unaware of the connection between HPV and anogenital cancers in men.8,15 Several studies also highlighted the fact that participants had minimal knowledge of HPV and its association with cervical cancer.20,22,24

Of the studies reviewed only one study focused solely on MSM. This Australian study found that although 74% of MSM surveyed had heard of the "wart virus" or HPV, only 30% had heard of the vaccine for HPV.13

Sources of HPV and HPV vaccine knowledge

Studies that examined high school or college students found that the majority of participants heard about HPV from health education classes/school, the media (including TV, newspapers, and magazines), a youth clinic, friends, or their parents.8,17,18

An Australian qualitative study found that males were more likely to obtain STI knowledge from their own personal experience with STIs and from playground banter at their high school.20 A Malaysian study found that men in the focus groups who were familiar with the HPV vaccine read about it from newspapers, magazines, and the Internet.24

One U.S. study that utilized focus groups found that participants stated they would most likely seek HPV information from the Internet and their healthcare provider. Other sources of information mentioned were clinics, schools, magazines, local TV news, and national TV advertisements.22 Another U.S. study specifically asked participants which type of media would be most likely to influence them to receive the HPV vaccine, 62.6% of the men indicated TV, followed by the newspaper (40.4%), the Internet (28.3%), magazines (27.9%), and the radio (24.4%).16

Men's interest and intent to receive the HPV vaccine

One U.S. study specifically assessed whether informing men about the benefits of male HPV vaccination for their female sexual partner(s) would boost interest in HPV vaccination versus if they were informed about the benefits to men alone. This study found that men reported moderate interest in the HPV vaccine and their acceptance of vaccination did not vary whether they received a self-protection message or a self-protection and partner protection message. This study also found that awareness of HPV, awareness of the HPV vaccine, and HPV knowledge were all positively correlated with vaccination intentions.8

An Australian study found that after informing participants about the cause and prevention of cervical cancer in women, 67.9% of the men agreed to personally receive the HPV vaccine if available.25 Several studies found that a majority of their male participants were more likely to accept the HPV vaccine if it also protected against genital warts in addition to cervical cancer.18,25,26

A study conducted in the United Kingdom found that after the provision of a brief HPV-related information message, 88% of study participants were supportive of HPV vaccination and 91.2% believed that boys should be vaccinated as well as girls. The study did not find significant gender differences in attitude toward HPV vaccination.19 Similarly, one study of Swedish high school students found that 74.3% of the male students surveyed expressed interest in getting HPV vaccinated after being provided with brief information about HPV, HPV-related cancers, and HPV vaccination and its cost.18 The Malaysian study found that once men in the focus groups were informed about the prevalence of HPV infection, many unmarried men expressed a desire to receive the vaccine for their own protection as well as to protect their future spouses.24 Likewise, the Australian study that examined attitudes of MSM found that after study participants were informed of their increased risk of anal cancer and asked to assume that the HPV vaccine would prevent most cases of anal and genital warts and anal cancer, 47% of the men in the study indicated that they would be willing to pay for the vaccination.13

Two studies showed relatively lower rates of male interest in HPV vaccination after participants were provided brief information messages about HPV and the HPV vaccine compared to the previous studies discussed. The first study found that only 37% of men were willing to receive the HPV vaccine after receiving information about HPV, the HPV vaccine, its protection of females against cervical disease, and its potential health benefits to males.15 The second study found that only 33% of 571 study subjects expressed interest in getting vaccinated against HPV, with 40% who were undecided, and 27% of men who did not want HPV vaccination.16

Factors affecting HPV vaccine acceptance

Several factors were found to affect vaccine acceptance among males. Studies found that sexual activity influenced men's acceptance of HPV vaccination. Men who had a higher number of lifetime sex partners were more likely to report greater interest in the HPV vaccine compared to men who were less sexually active or nonsexually active.5,8,15,26 Conversely, the Dutch study did not find an association between the acceptance of HPV vaccination and sexual activity, sexarche, and number of sexual partners.21

Perceived susceptibility was found to affect HPV vaccine acceptance in several studies.8,15,20,22,26 One study found that respondents who were married were among the most likely to decline the HPV vaccine. This study's participants expressed concern about receiving a vaccine they did not consider relevant to their current situation including being too old, in a monogamous relationship, or not sexually active.25 Similarly, another study found that men who were undecided about receiving the vaccine were more likely to be single and men who did not want the HPV vaccine were most likely to be living with a partner.5

Perceived benefit of getting vaccinated was another factor noted to affect male acceptance of the HPV vaccine.8,16,17 One study found that the perceived benefits of the HPV vaccine that were the most likely reasons for men to get immunized included a desire to stay healthy, to prevent cancer in sexual partners, and to prevent anal, penile, and head and neck cancers. Other frequently selected reasons in this study included a fear of cancer and to prevent genital warts.16 Similarly, a study of Swedish high school students demonstrated that both males and females thought that protection against an incurable disease would be the most motivating factor for STI vaccination.17

Several studies found that although knowledge of HPV among study participants was generally limited, it did not impact vaccine acceptance, which was moderate to relatively high.8,15,18,20,21,25 It should be taken into account, however, that many of these studies measured attitudes toward HPV vaccination after the provision of brief information messages about the health consequences of HPV and the benefits of the HPV vaccine to the study participants. These studies collected baseline knowledge data before the provision of HPV vaccine information and before measuring HPV vaccine acceptance attitudes.8,15,18,25 Additionally, a U.S. study of university men and women found that participants who were more knowledgeable about HPV demonstrated greater intent to receive the HPV vaccine.26

Perceived norms for HPV vaccination may also play an important role in vaccine acceptance among males. A study conducted in the United States found that young adult men who believed their friends would get HPV vaccinated reported a higher intent to get vaccinated themselves.8 Similarly two other studies found that men would more likely accept the HPV vaccine if it were recommended by a spouse, parent, or friend.16,26 Participants of a focus group study identified stigma associated with obtaining a vaccine preventing an STI as a potential barrier to HPV vaccination.22

Physician recommendation was another important factor that studies found to affect men's acceptance of HPV vaccination. Several studies demonstrated that men would be more likely to accept the HPV vaccine if their physician recommended it.5,15,16,26

Cost was also a major factor found to influence the decision of whether or not to obtain the HPV vaccine in several studies.8,16,18,20,22,23,26 The study conducted in Malaysia found that almost all of the focus group participants cited high cost of the HPV vaccine as a key barrier to vaccination.24

Several studies found that factors such as research-based safety and efficacy of the HPV vaccine in addition to vaccine adverse reactions were other important considerations that would influence men's HPV vaccination decisions.5,23-25

Data from the various studies were conflicting as to whether or not there were demographic correlates for male acceptance of the HPV vaccine. Some studies found no demographic correlates for vaccine acceptability.8,15,26 Other studies found that younger study participants were more likely to agree with HPV vaccination compared to older participants.5,21,25 Data regarding correlates of race with acceptance of HPV vaccination also varied between studies.5,26

Conclusion

The majority of studies worldwide have shown that men's knowledge of HPV, HPV-related diseases such as genital warts and cervical cancer, and the HPV vaccine is limited. This perhaps can be attributed to how the quadrivalent vaccine, Gardasil, was popularized and marketed as the "cervical cancer vaccine" because it was only previously approved for use in women.8 With the recent approval of Gardasil for males ages 9 through 26 years, it is necessary to emphasize the importance of vaccinating males for their own protection as well as for the protection of their sexual partners. Education initiatives should underscore the need to vaccinate both sexes to shift the burden of responsibility of HPV prevention solely from women's hands.26

Common sources of HPV and HPV vaccine information that were identified in the studies included health education classes/school, TV, youth clinics, newspapers, magazines, and the Internet. These media outlets need to be further examined in future studies to determine the most effective avenues for information dissemination.

Despite their limited knowledge of HPV and the HPV vaccine, it is encouraging to note that many of the studies found that men generally demonstrated interest in HPV vaccination after being given brief information messages regarding HPV and the HPV vaccine.8,15,18,25 Efforts should therefore be made to educate the public about the prevalence and consequences of HPV infection and to emphasize the advantages of vaccination.26

A few studies also demonstrated that men were more likely to agree to HPV vaccination if it also prevented against genital warts in themselves in addition to cervical cancer in their sexual partner(s).18,25,26 These findings, if consistent in future research, could have important implications as far as marketing of the quadrivalent vaccine. Education messages may need to place equal, if not more, emphasis on the fact that Gardasil protects against low-risk HPV types responsible for genital warts to increase HPV vaccine uptake among males.

Many factors were found to influence HPV vaccine acceptance among men. These included sexual activity, perceived susceptibility to HPV, perceived benefits of the HPV vaccine, perceived norms for vaccination, physician recommendation, cost, vaccine adverse reactions, and vaccine research-based safety and efficacy.5,8,15-18,20,22-26 Knowledge of these influencing factors can guide educational initiatives directed at men to increase their intent to get HPV vaccinated. Existing evidence shows that campaigns need to focus on risk factors for acquiring HPV because sexual activity and perceived susceptibility were found to be influential. Clinicians, including advanced practice nurses, need to encourage male HPV vaccination as physician recommendation was also found to increase vaccine uptake.

Finally, there were conflicting data as to the influence of demographic variables on male acceptance of the HPV. Future studies need to address whether demographic factors influence vaccine acceptance as this can provide valuable information as to specific target populations for educational and media campaigns.

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