Gardasil will continue to dominate the U.S. cervical cancer vaccine market despite the expected launch of a competitor from GlaxoSmithKline, Merck & Co's chief executive said on Thursday.

With the profile of the vaccine and the head start we have, it should be an advantage for us, Richard Clark told Reuters during a visit to London.

We are very comfortable with Gardasil's profile. In the parts of the world where physicians have the choice between two HPV vaccines, in a substantial majority of cases Gardasil is chosen. The market share in Europe for Gardasil is around 78 percent.

Clark said he hoped Merck's head start in the United States would keep it even further ahead there when Glaxo's Cervarix reaches the market.

Glaxo won a U.S. panel's support for its vaccine on Sept. 9, following a series of delays. The Food and Drug Administration usually follows panel recommendations and Glaxo said a final decision on Cervarix may come as early as this month.

Both Gardasil, which won FDA approval in 2006, and Cervarix protect against infection with the sexually transmitted human papillomavirus (HPV), which causes cervical cancer and genital warts.

Global sales of Gardasil topped $1.2 billion in 2008 but growth has slowed recently in markets where the initial group of eligible teenage girls has now been immunised.

Clark, however, said he saw room for additional sales if, as hoped, the vaccine is approved for older women and males.

There is still a tremendous opportunity for HPV, for Gardasil, not only in the United States but on a global basis, he said. (Editing by Greg Mahlich)