LONDON (Reuters) - A sexually transmitted virus that causes cervical cancer is also to blame for half of all cases of cancer of the penis, Spanish researchers said on Tuesday.

The finding suggests already available human papillomavirus (HPV) vaccines for cervical cancer are also likely to be effective in the fight against penile cancer, doctors from the Catalan Institute of Oncology in Barcelona said.

Merck & Co’s Gardasil and GlaxoSmithKline’s Cervarix are both used widely to immunize girls against HPV infection, which can lead to cancer of the cervix.

Penile cancer is much rarer, accounting for less than 1 percent of adult male cancers in Europe and North America, although the incidence can be as high as 10 percent in parts of Africa and Asia. Worldwide, there are more than 26,000 new cases every year.

Dr. Silvia de Sanjose and colleagues reviewed cases of penile cancer reported in clinical studies between 1986 and 2008 and found 46.9 percent of tumors were associated with HPV.

Nearly all of these were linked to HPV strains 16 and 18, the two types that most commonly cause cervical cancer and which are targeted by Gardasil and Cervarix, they wrote in the Journal of Clinical Pathology.

Merck reported results of a clinical trial last November showing that Gardasil was effective in preventing lesions caused by the virus in men.