Merck (NYSE:MRK), a Motley Fool Income Investor recommendation, recently released some highly promising data on an experimental drug with a very large potential market. In a strange twist, though, the drug's versatility could pose problems. Merck will have to tread carefully, as it faces a delicate task in marketing the treatment, should it be approved.

The drugmaker disclosed new information yesterday on Gardasil, its experimental recombinant vaccine to prevent infection by human papillomavirus (HPV), a common sexually transmitted virus linked to several conditions, including genital warts and cervical cancer. Merck's data showed that Gardasil was 100% effective in preventing high-grade cervical pre-cancers and non-invasive cervical cancers associated with two versions of the virus.

Merck expects to submit a Biologics License Application for Gardasil with the Food and Drug Administration in the fourth quarter. If approved, Gardasil would confront a huge market, since potentially every woman not infected with HPV could be vaccinated. Admittedly, fellow Income Investor pick GlaxoSmithKline (NYSE:GSK) is also working on a similar experimental vaccine, Cervarix. However, Gardasil is farther ahead in development, and in addition to protecting against HPV 16 and 18, the versions of the virus implicated in cervical cancer, Gardasil also helps reduce infection by HPV 6 and 11, the cause of most cases of genital warts.

Paradoxically, though, Gardasil's effectiveness against the last two types of HPV may work against the vaccine. HPV vaccines have the best chance of working when administered to women as young as 11 years old, before potential exposure to the virus via sexual activity. Some conservative groups have objected to HPV vaccines on the grounds that they could encourage premarital sex among teens, arguing that girls who know they are vaccinated against HPV may feel they have a green light to have sex.

HPV vaccines' potential to prevent cervical cancer could mute some conservatives' objections. However, Gardasil's ability to block forms of the virus associated with genital warts may make the treatment more objectionable than Cervarix to conservatives, since Cervarix is limited to preventing the forms of the virus connected to cervical cancer.

The latest results from Gardasil show that Merck's scientific foundations remain strong. However, the marketing department has its work cut out for it if it hopes to dodge the landmines associated with the vaccine.

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Fool contributor Brian Gorman is a freelance writer in Chicago. He does not own shares of any companies mentioned in this article.