Maybe it’s the sports fanatic in me, but I love a good head-to-head clinical trial. In a trial against a placebo, a company can only hurt itself. But if a drug fails head-to-head against a rival, the company gets hurt, and its competitor gets a boost. It takes guts for a company to put itself on the line like that.

Then again, GlaxoSmithKline (NYSE:GSK) didn't have much of a choice. Merck's (NYSE:MRK) human papillomavirus (HPV) vaccine Gardasil was first to the U.S. market, and the easiest way for Glaxo's second-fiddle, Cervarix, to compete is to show that it works better than the top dog.

Data from a trial presented today seems to suggest that the vaccine performs better, but Glaxo may have used the wrong measurement to make a definitive conclusion. Instead of looking at the rate of infection with HPV in females, which is what the vaccine is actually preventing, Glaxo looked at antibody levels in the patients. While higher antibody levels seen in patients that received Cervarix might result in a lower infection rate, the extra antibodies could also be circulating in the bloodstream, doing nothing. It's kind of like determining the winner of a baseball game based on the number of hits. The team with the most hits often wins, but not always. And besides, that's not the point of the game.

Vaccines have become an integral part of the business for companies like Glaxo, Merck, Novartis (NYSE:NVS), and sanofi-aventis (NYSE:SNY). That's one of the main reasons that Pfizer (NYSE:PFE) wanted to get its hands on Wyeth (NYSE:WYE). If a vaccine becomes used routinely, it's hard for a competitor to come along and unseat it.

Unfortunately for Glaxo, I don't think this data will be enough to help Cervarix knock Gardasil from the top spot, should the FDA approve Cervarix later this year. Doctors will need to see the final score before they'll switch teams.

Further Foolishness:

Pfizer is an Inside Value selection. Novartis is a Global Gains pick. Glaxo is a former selection of the Income Investor newsletter. Whether you like your companies big or small, dividend-laden or bursting with multibagger potential, we've got a newsletter for you.

Fool contributor Brian Orelli, Ph.D., doesn't understand the rules of cricket, but he'll still watch it if he catches a match while channel-surfing. He doesn't own shares of any company mentioned in this article. The Fool's disclosure policy can bowl a wicked googly.