HPV vaccine prevents anal intraepithelial neoplasia in young gay men

Cervical and anal cancers have much in common. Both develop from intraepithelial neoplasia and are associated with human papillomavirus (HPV) infection, most notably types 16 and 18. Anal cancer is rare, but its incidence has been increasing by about 2% each year, both among men and women. Men who have sex with men, people with HIV, women with cervical or vulvar cancer, and people taking immunosuppressants are at increased risk compared with the general population.

A trial tested the quadrivalent HPV vaccine against placebo in 602 healthy men who have sex with men. All were 16 - 25 years old. During 3 years of follow-up, no occurrences of anal cancer were seen either in those randomised to the vaccine or in those who received placebo. However, anal intraepithelial neoplasia developed in 74/275 men in the vaccine group compared with 103/276 in the placebo group, giving the efficacy of the vaccine for any type of HPV as 25.7% (95% CI 1.1 - 45.6%). The difference was more pronounced for anal intraepithelial neoplasia associated with types 16 and 18 HPV (12/275 and 27/276; 55.2%, 8.5 - 79.3%). Persistent infection with any type of HPV was seen in 51/275 of those allocated to the vaccine, compared with 113/276 with placebo, a reduction of 59.4% (43.0 - 71.4%). In the analysis by type of HPV, persistent infection with type 18 (7/275 and 26/276; 73.6%, 37.5% to 90.3%) was reduced the most.

Results of the per protocol analyses, comprising about two-thirds of all participants, showed even more convincingly the potential of the quadrivalent HPV vaccine to protect against anal intraepithelial neoplasia and persistent infection with HPV, and thus possibly against anal cancer.

No serious adverse effects were recorded in the placebo group compared with two in the vaccination group – an allergic reaction to peanuts and a seizure caused by fever related to varicella.

Palefsky JM et al. N Engl J Med 2011;365:1576-1585.

Bridget Farham