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Targeted human papillomavirus vaccination of men who have sex with men in the USA: a cost-effectiveness modelling analysis

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Summary

Background

A vaccine targeting human papillomavirus (HPV) types 16 and 18, which are associated with 80% of anal cancers, is efficacious in men. High-risk populations such as men who have sex with men (MSM) might especially benefit from vaccination. I aimed to estimate the cost-effectiveness of HPV vaccination of MSM in the USA.

Methods

I constructed decision-analytic models to estimate the direct health and economic outcomes of HPV vaccination (against types 6, 11, 16, and 18) for prevention of HPV-related anal cancer and genital warts. The model parameters that were varied were age at vaccination (12 years, 20 years, and 26 years), previous exposure to vaccine-targeted HPV types, and prevalence of HIV-1. I used the models to conduct sensitivity analyses, including duration of vaccine protection, vaccine cost, and burden of anal cancer and genital warts.

Findings

In a scenario of HPV vaccination of MSM at 12 years of age without previous exposure to HPV, compared with no vaccination, vaccination cost US$15 290 per quality-adjusted life-year gained. In scenarios where MSM are vaccinated at 20 years or 26 years of age, after exposure to HPV infections, the cost-effectiveness ratios worsened, but were less than $50 000 per quality-adjusted life-year under most scenarios. For example, HPV vaccination of MSM at 26 years cost $37 830 per quality-adjusted life-year when previous exposure to all vaccine-targeted HPV types was assumed to be 50%. Outcomes were most sensitive to variations in anal cancer incidence, duration of vaccine protection, and HIV prevalence in MSM.

Interpretation

HPV vaccination of MSM is likely to be a cost-effective intervention for the prevention of genital warts and anal cancer.

Funding

US National Cancer Institute.

Introduction

In 2009, there were 2100 new cases of and 260 deaths from anal cancer in men in the USA.1 Nearly 80% of these cases were associated with two oncogenic types of human papillomavirus (HPV), types 16 and 18, which also cause 70% of cases of cervical cancer.2 Although incidence of anal cancer is far lower than that of cervical cancer in the USA, the risk of anal cancer in men who have sex with men (MSM)—especially those who are HIV-positive—is comparable to, if not greater than, the risk of cervical cancer before routine cytology-based screening began.3

Two licensed prophylactic vaccines that target HPV 16 and 18 have high, sustained efficacy against persistent type-specific infections and cervical lesions in women unexposed to these HPV types. One of these vaccines is quadrivalent, also targeting HPV 6 and 11, which are low-risk for cancer, but are associated with most cases of genital warts, and this vaccine has shown high efficacy against incident genital warts and vaginal and vulvar lesions.4, 5, 6, 7, 8 On the basis of these data, HPV vaccination guidelines since 2007 have recommended routine vaccination for girls aged 11–12 years (and as young as 9 years) and catch-up vaccination for women up to 26 years of age.9, 10 Data for efficacy of the quadrivalent vaccine in men suggest that prevention of vaccine-type HPV infections and diseases, particularly genital warts, could be as high as 90%.11, 12 In October, 2009, the US Centers for Disease Control and Prevention (CDC) took a permissive stance on the use of the quadrivalent HPV vaccine in boys and men aged 9–26 years in the USA for prevention of genital warts, stopping short of recommending routine use.13

Data available since the 2009 CDC recommendation show that the quadrivalent vaccine has high efficacy for prevention of anal lesions in young men, and specifically in MSM.14 On the basis of these data, the Advisory Committee on Immunization Practices (ACIP), which advises the CDC, revisited the evidence on vaccine efficacy in men in October, 2010, and intends to reconsider recommendations for boys and men in the near future. Although previous analyses have shown that HPV vaccination should be targeted to preadolescent girls and that routine vaccination of boys might not be a good investment of health dollars unless coverage of girls remains low,15, 16 MSM may benefit differentially from HPV vaccination than the general male population, and might be an important target population. Many complex factors should be considered for assessment of strategies that target MSM for HPV vaccination, including uncertainties about the epidemiology of HPV-related diseases and vaccine properties in MSM, and barriers that might impede the successful implementation of such strategies. For example, identification of MSM might not occur until after sexual initiation and exposure to HPV infections, resulting in lower vaccine effectiveness. A survey17 in Australia reported that most MSM would access the HPV vaccine but not until the age of 20 years, which was 2 years after sexual debut and after a median of 15 sexual partners.

Despite the uncertainties, the potential value of vaccination of MSM is explicitly being discussed as part of the deliberations about HPV vaccination of boys and men in the USA. In particular, the recommendation to routinely vaccinate the male population might be swayed by evidence of the benefits and cost-effectiveness of HPV vaccination of MSM, especially if these outcomes hinge on the achievement of high coverage at an early age when the targeting of this population might be infeasible. No one empirical study can consider all the complex factors necessary for informed decision making; however, the use of mathematical disease models can help the synthesis of available data and the assessment of the cost-effectiveness of alternative strategies within different scenarios of uncertainty. To inform the upcoming deliberations of the ACIP and CDC on male HPV vaccination, I used mathematical models to project the cost-effectiveness of targeted HPV vaccination of MSM in the USA.

Section snippets

Modelling procedures

I used Markov cohort simulation models to synthesise epidemiological, quality of life, and cost data for HPV-related anal cancer and genital warts in MSM and to estimate direct health and economic effects of targeted HPV vaccination. The models comprise mutually exclusive health states that represent the true underlying health status of the population (ie, no disease, disease, or dead). The timescale of the analysis incorporated a cohort's entire lifetime and was divided into equal time

Results

For base-case assumptions of 50% vaccination coverage and 90% vaccine efficacy, HPV vaccination of MSM at age 12 years (before HPV exposure) had a cost-effectiveness ratio of $19 070 per QALY gained, when compared with no vaccination and only assessing prevention of anal cancer. When prevention of genital warts was included, the cost-effectiveness ratio decreased to $15 290 per QALY (figure). If MSM were vaccinated at 20 years or 26 years and had previous exposure to vaccine-type HPV

Discussion

My analysis suggests that HPV vaccination of MSM can protect against cases of vaccine-type anal cancer and genital warts for less than $50 000 per QALY in a range of scenarios of vaccine effectiveness and incidence of anal cancer and genital warts. Chiefly, results were robust irrespective of age at vaccination and proportion of MSM who have been exposed to vaccine-type HPV infections by the time of vaccination. Effectiveness of vaccination in reducing the incidence of anal cancer cases was the

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