Evaluating Cost-effectiveness of 9-valent HPV Vaccination for Men Who Have Sex with Men by HIV Status in Hong Kong
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Background
Human papillomavirus (HPV) is the most common sexually transmitted infection and a leading cause of anal cancer and genital warts, particularly among men who have sex with men (MSM). In Hong Kong, HPV vaccination is currently only offered to school-aged girls, despite the high burden of HPV-related diseases among MSM, especially those living with HIV. Existing cost-effectiveness evaluations of HPV vaccination in Hong Kong primarily focus on female-only strategies and heterosexual men without accounting for differences in HPV infection risks among MSM. In contrast, countries such as the United Kingdom initially implemented free HPV vaccination for MSM through sexual health clinics, followed by an expansion of the programme to include adolescent boys. This provides a potentially useful model for Hong Kong to consider. This study aimed to evaluate the cost-effectiveness of implementing 9-valent HPV (9vHPV) vaccination strategies among HIV-positive and HIV-negative MSM in Hong Kong.
Methods
We developed a Markov model to simulate the natural history of HPV infection and progression to genital warts, and anal cancer in a cohort of 100,000 MSM in Hong Kong, stratified by four age groups (12–18, 19–27, 28–45, and >45 years) and HIV status (positive or negative). A 10-year time horizon was used from the healthcare provider’s perspective. The primary outcome was the incremental cost-effectiveness ratio (ICER) per quality-adjusted life-year (QALY) gained. One-way and probabilistic sensitivity analyses were performed to assess the robustness of the results.
Results
Modelled incidence rates of anal cancer and anogenital warts were significantly reduced following the implementation of 9vHPV vaccine strategies. Vaccinating all MSM aged ≥12 years prevented the most anogenital warts (52.5%) and anal cancer cases (70.4%). Across all MSM vaccination strategies assessed, the ICERs were below the willingness-to-pay (WTP) threshold of USD 50,696 per QALY gained (one-time Hong Kong GDP per capita) or cost-saving, indicating that all 9vHPV strategies were cost-effective. In probabilistic sensitivity analyses, the vaccination strategy for MSM aged ≥12 years consistently demonstrated a high probability of being cost-effective. Furthermore, when the cost of the 9vHPV vaccine decreased or the time horizon was extended, the ICERs for vaccinating MSM aged ≥12 years further declined, making the strategy more cost-effective.
Conclusion
Our findings support the implementation of 9vHPV vaccination for MSM in Hong Kong, with vaccinating all MSM aged ≥12 years offering the greatest health and economic benefits.
Research in context
Evidence before this study
Many countries, such as the United Kingdom, Australia and the United States, have implemented HPV vaccination strategies that include males. In 2018, the UK provided free HPV vaccination for MSM aged ≤45 through sexual health clinics, and later expanded the national HPV programme to include 12–13-year-old boys starting in 2019 to accelerate the reduction of HPV-related cancers in men [1, 2]. This stepwise approach—starting with MSM and later expanding to boys—may be a feasible model for Hong Kong to consider. However, in many settings, the inclusion of males in HPV vaccination programmes is not cost-effective, primarily due to high vaccine coverage among females, which provides indirect protection to males through herd immunity. In Hong Kong, the school-based HPV vaccination program targets only adolescent females. Most cost-effectiveness studies have focused on female-only or gender-neutral strategies without specifically evaluating men who have sex with men (MSM), who are at a substantially higher risk of anal cancer compared to the general population (an estimated 37-fold increased risk in the United States) [3]. HIV-positive MSM are at even greater risk due to their immunocompromised status.
We searched PubMed, Google Scholar for articles published between Jan 1, 2000, and March 31, 2024, using terms such as “HPV vaccine”, “MSM”, “cost-effectiveness”, “HIV”, and “Hong Kong”. We found that there is no study evaluating HPV vaccination strategies specifically for MSM in Hong Kong. Existing models primarily address HPV transmission in heterosexual populations. Although a few studies from nearby regions (e.g., mainland China and Singapore) have assessed HPV vaccination among MSM, none have incorporated HIV status in their analyses. These gaps highlight the importance of MSM-specific evaluation of HPV vaccination strategies in Hong Kong.
Added value of this study
We did a cost-effectiveness analysis to evaluate 30 vaccine strategies in Hong Kong. These include a combination of 9vHPV at different age groups and HIV status MSM aged ≥12 years. Our findings show that vaccinating all MSM aged ≥12 years is the most cost-effective strategy under base-case assumptions, offering the greatest reductions in the incidence of anogenital warts, anal cancer. This strategy remained the most cost-effective across a range of vaccine costs, particularly when prices decrease and the time horizon increases to 20 years.
Implications of all the available evidence
Vaccinating MSM with the 9vHPV is cost-effective in Hong Kong. Among all strategies assessed, vaccinating all MSM aged ≥12 years offers the greatest health and economic benefits, preventing the largest number of HPV-related disease cases while remaining highly cost-effective under the one-time GDP per capita threshold. Although the evaluation from a healthcare provider’s perspective confirms strong cost-effectiveness, affordability remains a key barrier at the individual level—over 50% of MSM consider the high cost of the HPV vaccine a major obstacle to uptake [4]. These findings highlight the importance of publicly subsidized vaccination programs for MSM, similar to how the Hong Kong Childhood Immunisation Programme (HKCIP) provides the 9vHPV vaccine for girls. The findings may also provide valuable policy evidence for other regions or countries that have not yet introduced MSM-specific 9vHPV vaccination strategies.
