There is a “strong” argument for extending UK HPV (human papillomavirus) vaccination programmes to young gay men, according to an editorial published in the August edition of Sexually Transmitted Infections. The authors highlight the high incidence of HPV-related anal disease in gay men and data illustrating the efficacy and cost-effectiveness of vaccination for gay men aged 26 and younger.
Persistent infection with certain high-risk strains of HPV (especially HPV 16 and 18) can lead to the development of pre-cancerous and cancerous cell changes in the cervix or anus. Incidence of HPV-associated anal disease is higher among gay men than any other group. Vaccines have been developed that provide excellent protection against cancer-associated HPV types.
The vaccines work best before sexual debut and the HPV vaccine programme in the UK has prioritised school-aged girls. The theory has been that “herd immunity” would also have benefits for boys. However, Australia has extended its HPV vaccination scheme to include boys.
Despite their high risk of HPV-associated anal disease, vaccination is not recommended for gay men in the United Kingdom or elsewhere.
The authors of the editorial – all of whom are sexual health physicians – argue that this should change. They show that possible objections to this strategy are baseless.
Recent studies involving HIV-negative gay men with between one and five sexual partners have shown that the quadrivalent HPV vaccine (Gardasil, the product used in the UK school vaccination scheme since 2012) is strongly immunogenic and is effective at preventing infection, reducing HPV persistence and preventing the development of external warts. In addition, vaccination was also shown to reduce rates of pre-cancerous anal lesions. The vaccine was most effective in people without baseline infection with the HPV types covered by the vaccine. However, it also had acceptable levels of efficacy in individuals with evidence of existing HPV 16 or 18 infection.
Other research has also shown that Gardasil is immunogenic in HIV-positive gay men. In men with and without baseline HPV 16 or 18 infection, immunisation produced protective antibodies against the four HPV types covered by the vaccine in at least 98% of people.
There are data showing that immunisation would be of benefit to the vast majority of sexually experienced younger gay men.
The investigators draw especial attention to a meta-analysis showing that prevalence of anal infection with HPV 16 and 18 in HIV-negative gay men was 13% and 5%, respectively. Separate research showed that only 19% of gay men aged 35 and younger were infected with HPV 16 at baseline. “Seroincidence remained above 3% per year until age 45 years, illustrating the value of HPV vaccination,” write the authors.
Analysis of urine samples obtained from patients attending sexual health clinics in the UK showed that prevalence of any high-risk HPV strain was below 5% among gay men aged under 25, and that fewer than 10% of men in the 24 to 44 age group were infected with these HPV types.
The investigators acknowledge that urine samples can underestimate the prevalence of anal HPV infection. Nevertheless, they believe the data give “some support to the hypothesis that a majority of young MSM will be unexposed to HPV 16 or 18”.
US research has shown that targeted HPV vaccination in younger gay men is cost effective. The Centers for Disease Control and Prevention now recommends universal vaccination for boys aged 11 and 12, and vaccination for gay men up to the age of 26.
In 2010, 17,000 gay men aged between 16 and 26 attended a sexual health clinic in the UK, and the investigators propose that these clinics would provide an ideal host for the vaccination programme.
“An HPV vaccination programme would build upon a long-stranding programme of vaccination of MSM for hepatitis B which has an uptake of 85%,” comment the investigators.
They conclude, “recent data illustrates HPV vaccination of sexually active MSM is effective, and modelling using conservative analysis suggests vaccination is cost-effective…the argument for introducing targeted HPV vaccination for MSM up to age 26 years is strong.”
The UK's Joint Committee on Vaccination and Immunisation will decide whether vaccination of MSM aged 26 and under is cost-effective in 2014 after the completion of age-related prevalence surveys and cost-effectiveness modelling.
Lawton MD et al. HPV vaccination to prevent anal cancer in men who have sex with men. Sex Transm Infect, 98: 342-43, 2013.