A large, international clinical trial led by doctors at the University of California, San Francisco, indicates that Gardasil, a vaccine which has been shown to be safe and effective in preventing infection with the human papillomavirus (HPV) also reduced the rates of pre-cancerous cell changes among men who have sex with men.

The study was reported in the 27 October 2011 issue of New England Journal of Medicine.

Although anal cancer is less common than other forms of cancer, it disproportionately affects men who have
sex with men and HIV-positive people.

Anal cancer is caused by HPV, primarily HPV type 16 or 18, and is preceded by high-grade anal intraepithelial neoplasia (AIN) grade 2 or 3. Gardasil was effective in reducing the occurrence of AIN grades 2 and 3 among men in the study.

As anal cancer can take decades to develop, trials demonstrating Gardasil’s effectiveness against anal cancer
would need to run for many years.

The vaccine’s effectiveness in reducing AIN 2 and 3 is therefore significant, as it provides important indirect evidence suggesting a likely effect in reducing anal cancers.

The trial took place between 2006 and 2008 and involved a group of 602 men between the ages of 16–26 years from Australia, Brazil, Canada, Croatia, Germany, Spain and the United States.

All trial participants were men who have sex with men with a history of between one to five sexual encounters at recruitment.

The trial raises hopes that vaccination may help prevent anal cancers. ‘Based on these data, the vaccine works well to prevent HPV infection and precancerous anal disease, and will likelyprevent anal cancer in men,’ said Joel Palefsky, the trial chief investigator.

‘The ideal time to begin vaccination would be before initiation of sexual activity, but vaccination may also be useful after initiation of sexual activity.’

The Gardasil vaccine is administered free to young girls in Australia, as apreventative measure against cervical cancer. Earlier this year, CSL – the manufacturer of Gardasil – applied to the Australian Pharmaceutical Benefits Advisory Committee (PBAC) to extend the free Gardasil vaccination program to boys aged 12 to 13 years old.

CSL argued that ‘a gender-neutral vaccination strategy will have the greatest impact on HPV disease and is in the best interest of public health.’ The submission was rejected by PBAC due to concerns about cost and cost-effectiveness.

CSL is reapplying to PBAC to extend the free vaccination program to boys.

Disclaimer: AFAO is currently in negotiations with CSL regarding an unrestricted education grant to produce an information resource for gay and other men who have sex with men on HPV, vaccination and anal cancer.