According to a recent study, Cervarix, GlaxoSmithKline's vaccine against cervical cancer, has been shown to protect women for up to 4 and a half years from the virus that causes the disease. Cervical cancer is caused by infection with the human papillomavirus (HPV), a persistent infection with certain HPV types lead to cervical cancer. The study led by U.S. researchers, analyzed 776 women to whom they have given either the vaccine or three placebo shots. It was found that those who were given Cervarix produced and maintained high levels of antibodies against HPV types 16 and 18, the most common virus types associated with this type of cancer, for about 4 years after receiving the dose. HPV is spread by skin-to-skin contact and is the most common sexually transmitted disease in the U.S.A., cervical cancer being the second worldwide cause for death among women. "The high level of efficacy seen here against persistent infection might ultimately lead to a long-term prevention of HPV-16 and HPV-18 associated with precancerous and cancerous lesions," said Dr. Diane Harper of the Dartmouth Medical School in New Hampshire, coordinator of the research. If Cervarix will be approved, sales may reach $4 billion a year. GlaxoSmithKline estimated that "the consumers" that need this type of vaccine will spend up to $7 billion a year by 2010.