By Julie Steenhuysen

CHICAGO (Reuters) - Boys should be routinely vaccinated against the human papillomavirus or HPV in an effort to protect them from oral, anal and penile cancers, and to extend protection of girls from cervical cancer, U.S. vaccine advisers said on Tuesday.

The Advisory Committee on Immunization Practices, which advises the U.S. Centers for Disease Control and Prevention, voted unanimously to recommend routine use of Merck & Co's Gardasil in 11- and 12-year-old boys to fight the sexually transmitted virus, with 13 yes votes and one abstention.

Previously, the CDC had said doctors are free to use the vaccine in boys but had stopped short of recommending routine vaccination.

Boys aged 13-21 who have not been vaccinated should be given a catch-up dose of the vaccine, which is given in a three-dose series. Men aged 22 through 26 may be vaccinated but the vaccine is not recommended for routine use, the panel said.

Currently, the CDC recommends HPV vaccinations made by Merck and GlaxoSmithKline for girls and women between the ages of 11 and 26.

The prior recommendations were based largely on evidence that the vaccine protects boys from genital warts but the new recommendations reflect several studies showing the vaccine helps prevent cancers in boys as well, Dr. Anne Schuchat, director of the National Center for Immunization and Respiratory Diseases, said in a conference call with reporters.

The HPV vaccine offers an opportunity to decrease the burden of HPV in both males and females, Schuchat said.

"In addition to providing a direct benefit to boys, there is also the potential that the vaccine will reduce the spread of HPV from males to females," she said.

Schuchat noted that the HPV vaccine currently is not being as widely used among girls as hoped and vaccinating boys could help reduce transmission of HPV to girls.

POLITICAL CONTROVERSY

During the meeting, CDC experts advised the panel there is no evidence the vaccine can cause "mental retardation," a concern raised by Republican congresswoman Michele Bachmann in a Republican presidential candidate debate.

The U.S. medical community repudiated Bachmann's claim, which she made as a swipe at a rival, Texas Governor Rick Perry, who issued an executive order in 2007 mandating girls get the HPV vaccine as part of a school immunization program.

Perry's order was later overturned.

The committee's strong recommendations, which are subject to CDC approval, likely will mean insurance companies will begin paying for the vaccine when used in boys.

"Today's ACIP recommendations will help to provide greater access to Gardasil for males," said Dr. Mark Feinberg, chief public health and science officer, Merck Vaccines.

Insurance companies have largely considered the CDC's prior policy recommendation for boys as optional and some have refused to cover the shots for boys.

"I think it's a worthwhile vaccine," said Dr. Jay Siwek, a professor of family medicine at Georgetown University Medical Center, who was not part of the panel.

Siwek said the only downside of the vaccine is cost, which is $360 for a course of three shots.

In his own practice, Siwek tells parents the vaccine protects against cancers that occur in boys -- mostly mouth and throat -- and it helps protect girls from cancer as well.

Dr. Robert Haddad of Dana-Farber Cancer Institute, said there has been a epidemic of HPV-related head and neck cancers.

"HPV is a cause of many cancers so it is really important to support endeavors to vaccinate," he said.

The approval, which only applies to Merck's vaccine, may bolster sales of Gardasil, which have stalled amid competition from a rival GlaxoSmithKline product and because many younger women already have been immunized with Gardasil, limiting the market size.

Gardasil's sales hit $1.1 billion worldwide in 2009 and have been hovering in that range.

(Reporting by Julie Steenhuysen in Chicago, Editing by Sandra Maler and Bill Trott)