The human papillomavirus, HPV, is a category of over 200 related viruses. It is the most common sexually transmitted infection in the world, with over 40 types of transmissible HPV. While most HPV infections can be asymptomatic and can be cleared by the body’s immune system, there are several high-risk HPV strains that are linked to cancer risk. HPV-associated cancers include oropharyngeal, penile, vaginal, vulvar, anal, and, most infamously, cervical cancer. Cervical cancer is the eighth most diagnosed cancer, according to the World Health Organization Global Cancer Observatory, with 90% of cervical cancer cases due to persistent HPV infections. It is also estimated that more than 80% of sexually active adults acquire some form of HPV infection in their lifetime. These statistics highlight that even though, in most cases, an HPV infection is inconsequential, it can lead to grave adverse health effects. The development of the HPV vaccine, therefore, has not only been paramount in protecting against the spread of high-risk HPV infections, but also plays an instrumental role in cancer prevention.
Two HPV vaccines are widely used globally: GARDASIL® 9, developed by Merck, and CERVARIX®, manufactured by GSK. GARDASIL® 9 protects against nine HPV types, including the seven strains responsible for approximately 90% of cervical cancers, while CERVARIX® protects against HPV types 16 and 18, which account for the vast majority of cervical cancer cases worldwide. While GARDASIL® 9 has become the predominant HPV vaccine used in many high-income countries, including Canada, vaccine availability varies globally because of differences in regulatory approval, procurement strategies, supply, and cost. Access remains particularly challenging in some low- and middle-income countries, where vaccine introduction has historically been limited by affordability and supply constraints.
Since their introduction, HPV vaccines have produced measurable public-health benefits around the world. Studies from North America, Europe, and Australia have demonstrated substantial reductions in HPV infections and HPV-associated cancers following vaccine implementation. Vaccination programs have been associated with a reduction in oral HPV infections, contributing to lower future risks of oropharyngeal cancers, while similar benefits have been observed for anal cancer prevention.
The greatest impact has been seen in the prevention of cervical cancer, which only affects females. A recently published population-level study from England reported reductions in cervical cancer mortality ranging from 70–100% in women, depending on the age at vaccination. Furthermore, more than fourteen countries have documented substantial declines in HPV prevalence and cervical precancers following widespread vaccine uptake.
Although HPV vaccination programs were initially targeted toward girls because of the direct link between HPV and cervical cancer, many countries now recommend routine vaccination for both boys and girls. Vaccinating boys not only reduces their risk of HPV-associated cancers, including oropharyngeal, anal, and penile cancers, but also strengthens herd immunity by reducing viral transmission throughout the population.
Given the vaccine’s high efficacy against HPV infections, why have HPV-related cancers not been eliminated yet? One major category of barriers to its widespread success relates to healthcare infrastructure, affordability, and vaccine delivery systems. In many low-resource settings, limited healthcare facilities, shortages of trained personnel, and weak vaccine distribution networks make consistent vaccine access difficult. Maintaining vaccine supplies and ensuring completion of recommended dosing schedules can be particularly challenging in rural and underserved regions. Although organizations such as Gavi, UNICEF, and the World Health Organization have worked to reduce vaccine costs and support immunization programs, affordability remains a barrier in many countries. Ongoing armed conflict and political instability can further disrupt healthcare systems, limiting access to routine vaccination services.
A second set of barriers involves vaccine acceptance and public perception. Concerns about vaccine safety, distrust of governments or pharmaceutical companies, and exposure to misinformation can reduce vaccine uptake. Cultural beliefs and stigma surrounding sexually transmitted infections may also discourage vaccination. In some communities, misconceptions persist that HPV vaccination encourages sexual activity, despite evidence showing otherwise. Gender bias can further complicate vaccine delivery; because HPV has historically been framed as a woman’s health issue, boys are often overlooked in vaccination campaigns, while girls may face cultural barriers that limit access to preventive healthcare services.
Encouragingly, several international initiatives are working to address these challenges. The WHO’s global strategy for eliminating cervical cancer aims to achieve 90% HPV vaccination coverage among girls by age 15, while organizations such as UNICEF and Gavi support vaccine procurement and delivery programs in low-income countries. School-based vaccination programs have been particularly successful in increasing vaccine uptake, and several countries have reported major improvements in coverage after introducing public education campaigns and reducing financial barriers to vaccination. There is also growing recognition of the importance of vaccinating boys, alongside girls, to maximize population-level protection against HPV-associated diseases.
The National Cancer Institute estimates that widespread global HPV vaccination could reduce cervical cancer incidence by as much as 90%. Achieving this goal will require more than scientific innovation. Gaps in healthcare infrastructure, vaccine affordability, public education, and vaccine acceptance must also be addressed. The HPV vaccine represents one of the most successful cancer-prevention tools ever developed, protecting against infection while dramatically reducing the risk of several cancers. Ensuring that these benefits reach populations worldwide may be one of the most important public-health challenges and opportunities of the coming decades.
Alina Mehra
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