A study of gay men in Ireland that has investigated the prevalence of infection with human papillomavirus (HPV), some types of which cause genital warts and cervical, anal and oral cancers, concludes that 47% of HIV-positive and 64% of HIV-negative gay men would benefit from being given one of the HPV vaccines against the two most common cancer-causing types.
Even though a much higher proportion of gay men than the general public are already infected with the strains of HPV most associated with cancer, and would not therefore benefit from a vaccine, they are still in the minority: and the fact that anal cancer is 17-35 times more common in gay men than the general public, and 35-70 times more common in HIV-positive gay men, makes vaccination with the HPV vaccines Cervarix (which offers near-100% protection against the two most common cancer-causing types of HPV) or Gardasil (which also offers 100% protection against the two most common wart-causing types) still worthwhile.
Researchers looked at HPV infection among 194 men who have sex with men who were recruited at GUIDE, the gay men’s health clinic at St James’s Hospital in Dublin, and the Gay Men’s Health Services (GMHS), a community-based gay men’s sexual health clinic, in April and May 2012. The cohort was split almost evenly between HIV-positive men (99) and HIV-negative men (95).
The average age of the cohort was 36, with the HIV-positive men older, on average, than the HIV-negative ones (40 versus 32). Three-quarters of the men were born in Ireland; the rest were split more or less evenly between western Europeans, eastern Europeans and men from the rest of the world.
In terms of sexual risk behaviour, there was almost no difference related to HIV status in the average number of partners in the last year (seven in HIV-positive and eight in HIV-negative men) or in condom use (43% of HIV-positive and 40% of HIV-negative men said they had always used condoms in the past year). Twelve of the HIV-positive men said they had had no sex at all in the previous year compared with only two of the HIV-negative men, and yet nine of these 14 had detectable HPV infection, seven with cancer-causing types.
(In the natural history of HPV infection, the body mounts an immune response to the virus that eventually results in the infection disappearing over a period from months to years: one reason HIV-positive people (not just gay men) have more anal and cervical cancer is because it takes longer for them to eliminate HPV from their system.)
Despite having slightly lower HIV risk behaviour, the HIV-positive men were more likely to have had a previous sexually transmitted infection (STI) diagnosed (70%) than the HIV-negative men (44%), though this could be partly influenced by age. Thirty-nine per cent of the HIV-positive men had had visible anal warts before compared with 14% of the HIV-negative men.
The cross-sectional study found that a majority (69%) of men had HPV infection with at least one type: 77% of the HIV-positive men and 61% of the HIV-negative men.
However, only a minority of men had infection with the two most common and virulent cancer-causing types, HPV16 and HPV18. Forty-seven per cent of the HIV-positive and 36% of the HIV-negative men had infection with either HPV16, HPV18, or both, or another cancer-causing type called HPV31, which is not covered specifically by the HPV vaccines, though they have some efficacy against it. Even those infected with one cancer-causing HPV type could benefit marginally from the HPV vaccine and while 12% of the HIV-positive men had both types 16 and 18, none of the HIV-negative men did.
The likelihood of having a cancer-causing type of HPV rose with age, with a quarter of 17 to 24-year olds having HPV 16, 18 or 31 but a half of men over 35. The same was not true of all HPVs including the wart-forming types: these were, in fact, most common in the youngest age group.
The likelihood of having both any HPV and cancer-causing types was unsurprisingly higher in men with a previous STI diagnosis or who had had anal warts. The likelihood was slightly higher in men who used condoms irregularly or never, compared with men who used them always: 36% of men who always used condoms had at least one cancer-causing HPV variety, 44% who sometimes used condoms and 56% of the small number of individuals who never did, but this trend was not statistically significant (p = 0.366). There was no association between HPV infection and type of sex: men who only had oral sex were as likely to have HPV as men who only had anal sex.
This study had a few limitations, the main one of which is that HPV infection rates observed in Dublin may not be generalisable to other areas. Nonetheless, where it had been previously assumed that HPV infection among sexually active gay men and in particular HIV-positive men was so universal as to make vaccinating them pointless, this study implies that at least half of HIV-positive gay men and two-thirds of HIV-negative gay men could benefit from it.
The study has appeared shortly before the UK government’s Joint Committee on Vaccination and Immunisation meets on Monday 29 September, as reported by the BBC, to consider whether adolescent boys, gay men or both should receive the HPV vaccine.
Cervarix was recommended for girls aged 12-13 plus ‘catch-up’ vaccinations for older women six years ago, and Gardasil replaced it in 2012. The presumption was that reducing HPV infection in women would also reduce it in men, but this does not apply to men who have sex with men. A number of countries already recommend the HPV vaccine for boys including the USA, which licensed Gardasil in young men in 2010.
HPV now causes at least 5% of the world’s cancers and it is estimated that if boys were vaccinated, the rate of anal cancer would fall by 60%.
The authors comment “Emerging patterns of HPV-related disease strengthen the call for universal vaccination of boys and girls with consideration of catch-up and targeted vaccination of high-risk groups such as MSM [men who have sex with men] and those with HIV infection.”
Sadlier C et al. Prevalence of human papillomavirus in men who have sex with men in the era of an effective vaccine: a call to act. HIV Medicine 15(8): 499-504, 2014.
