One sexual transmitted disease (STD) may have just met its match. On June 8, 2006 Merck & Company introduced the first-ever vaccine to prevent the human papillomavirus (HPV). The Food and Drug Administration (FDA) approved the use of the vaccine, to be sold under the name GARDASIL as prevention against four strains of the virus that causes genital warts and cervical cancer.

GARDASIL is a vaccine that comes in three doses over a period of six months and is supposed to last a lifetime. Each dose costs about $120-160, depending on which pharmacy you get the vaccine from. Currently, GARDASIL is only available in the United States and Mexico.

“Merck is proud to be the leader in cervical cancer vaccine research and development,” said Richard T. Clark, chief executive officer and president of Merck & Co., Inc. “Bringing forward this life-saving scientific advance is yet another testament to Merck’s long-standing mission to research and develop novel vaccines and medicines that can greatly improve public health.”

But as the fanfare surrounding the vaccine's approval dies down, researchers are confronting a difficult reality. As Joel Palefsky, M.D. of the University of San Francisco points out, even though about 80 percent of women will have contracted HPV by the age of 50, over 75 percent of women have never even heard of the disease. Merck is now joining with public health officials to launch a massive HPV awareness and vaccination campaign—a campaign that is already meeting resistance from social conservatives.

HPV 101

The human papillomavirus (pronounced pa-pil-oh-ma) is a sexually transmitted disease that produces genital and anal warts and can also cause cervical cancer. It can infect women as well as men and is passed on through genital contact, usually during vaginal or anal sex.

HPV can be transmitted whether or not you come in contact with a partner's bodily fluids (such as blood, semen or vaginal secretions) and may be passed on even if a person has no visible warts. It can infect both the skin that covers the outside of the body (called cutaneous HPV) as well as the skin that lines the mouth, vagina, the tip of the penis and the anus (known as mucosal HPV). Cutaneous HPV is usually the cause of genital warts.

There are about 100 different strains of HPV, more than 30 of which actually cause genital warts. Only about 10 of these 30 or so strains are know to cause cervical cancer. According to the Centers for Disease Control (CDC), at least 50 percent of sexually active people will get HPV at some point in their lives and each year about 6.2 million American will become infected with HPV.

Usually, most cases of HPV are fought off by the immune system within 1-2 years of infection. But in some women, HPV can cause cervical cancer. By undergoing regular Pap smear tests, a woman's gynecologist can watch for the earliest signs that her HPV infection may be heading down a cancerous path. With early detection, cervical cancer can usually be prevented.

The Vaccine: Fighting the Most Common Four

Even though there are over 100 different strains of HPV, GARDASIL will only protect against four strains: types 6 and 11, which cause 90 percent of all cases of genital warts, and types 16 and 18, which cause about 75 percent of all HPV-related cervical cancers.

While an ideal vaccine would protect against all 100 strains of HPV, developing such a vaccine would be a financial and logistical nightmare. Conducting the massive clinical trials necessary to prove the vaccine efficacy incurs enormous costs. For each of the four strains of HPV that the vaccine claims to prevent, researchers compared thousands of vaccinated women to thousands of unvaccinated women who then contracted that form of HPV. Now, imagine that process repeated 100 times over. By targeting the most threatening types of HPV, the developers at Merck have tried to pack the most punch into the vaccine, while still making it a financially viable endeavor.

The researchers gave GARDASIL to women who had not been previously exposed to HPV. Over time, they found that the HPV vaccine prevented 100 percent of all cervical cancers related to HPV types 16 and 18, and 99 percent of cases of genital warts caused by types 6 and 11.

GlaxoSmithKline Inc (GSK), another leading research-based pharmaceutical company, is currently working on a second HPV vaccine. GSK’s vaccine will be aimed at women aged 25-55 to prevent HPV types 16 and 18.

Prevention, Not a Cure

Unfortunately for the 20 million people already infected with HPV, GARDASIL can only prevent infection from taking place. It will not cure an existing HPV infection.

The only line of defense for those who already have HPV is a Pap test. When taken on a regular basis, the Pap test can detect abnormal cell growth before the cells turn cancerous. According to the CDC, most women diagnosed with cervical cancer have never had a Pap test.

For this reason, the vaccine is being recommended for all women ages nine through 26. Merck is trying to make the vaccine widely available by providing free inoculations to adults and adolescents who are uninsured or otherwise unable to afford the vaccine. By vaccinating young women before they become exposed to HPV, public health officials hope to head off the spread of this disease and prevent future cases of cervical cancer.

Opposition to the Vaccine

It is precisely this desire to head off the disease in young women that has social conservatives up in arms. These opponents claim that early HPV vaccinations will only promote sexual activity among teens. They claim that abstinence is the only sure way to prevent the spread of HPV and vaccinating teens will send the false message that it is now "safe" to have sex.

Jack Sobel, M.D., professor of medicine and chief of infectious diseases at Wayne State University School of Medicine in Detroit, responded to this critique in an interview with Medscape saying, “It is beyond belief that there has been public opposition to and protesting against a vaccine that will save lives… The concern of increased promiscuity is incomprehensible.”

Prior to their campaign against the HPV vaccine, these social conservatives used HPV as a case in point for their crusade against condom use. They claimed that condoms could not effectively protect a person from coming in contact with warts that lay outside the area covered by the latex. Therefore, they reasoned, condoms should not be promoted as an effective means of preventing STDs. However, an article in the June issue of the New England Journal of Medicine found condoms to be highly effective in preventing the transmission of HPV.

What about Men?

Men may become infected with HPV just as easily as women, and they are just as likely to spread this disease to their partners. Just like women, most men who become infected with HPV will also have no visible symptoms.

But there are differences in the way HPV affects men and women. First, other than the presence of genital warts (examined by a dermatologist), there is no easy way to test for HPV in men (women have Pap tests). Second, unlike cervical cancer in females, it is very rare that a male will develop anus or penile cancer due to an HPV infection. Nevertheless, it’s necessary to find a way to detect HPV in men so as to prevent transmission of the virus to women. Currently, a blood test is being developed that will detect HPV in men.

This does not mean, however, that the HPV vaccine can't be used in men. Trials are underway to determine if vaccinating young men will be an effective next step in preventing the spread of this disease. Laura Koutsky, Ph.D., from the HPV research group at the University of Washington in Seattle was one of the investigators on the female vaccination trial. Dr. Koutsky believes that, based on previous research, battling this disease in both men and women will be the most effective approach.