million people. In most people, the infection is entirely asymptomatic and causes no disease. However, in some people, HPV can cause genital or anal warts, recurrent respiratory papillomatosis (RRP) lesions, and/or cancer, most notably of the cervix. Cervical cancer is the 11th most common cancer among US women, and the second most common cause of cancer in women worldwide. An estimated 9,710 new cases of cervical cancer will occur in the United States alone in 2006, and 3,700 women will die from it. Although the conditions it causes may be treatable, HPV infection has no treatment, and use of condoms may not prevent HPV transmission. (See Centers for Disease Control and Prevention (CDC) links in section 8 of the Search Summary) Other cancers thought to be caused by HPV include vaginal, vulvar, and head and neck cancer. Additional information on HPV and HPV-related diseases can be found through the Web sites listed in section 8 of the Search Summary.
Two major pharmaceutical companies have developed vaccines for HPV. These vaccines are administered in three injections: at day 1, month 2, and month 6. There are over 100 known strains of HPV, but only a few have been causally associated with cancer. Vaccines are intended to protect against the most dangerous strains of HPV. The following paragraphs include details from an Advisory Committee on Immunization Practices meeting held at the CDC in February 2006 regarding these vaccines. (See link in section 8 of the Search Summary)
GlaxoSmithKline has produced a recombinant vaccine (Cervarix) against HPV strains 16 and 18, which are the strains responsible for 70% of cases of cervical cancer. This vaccine has been tested in 1,113 women for over two years. It was found to be well tolerated, with minimal, minor adverse events. It was also found to be highly efficacious, with 100% protection against persistent HPV (meaning the infection has not resolved within six months and is therefore more likely to lead to pathological changes) caused by the target strains. Through the follow-up period, 93% of patients had normal pap smears. 53 months after vaccination, 98% of patients still had HPV antigens thought to be protective. Phase III studies enrolling more than 30,000 patients internationally are currently underway.
Merck & Co. has developed a vaccine (Gardasil) against HPV strains 16 and 18, as well as strains 6 and 11. Together, these strains account for more than 90% of cases of genital warts and RRP, in addition to protecting against cervical cancer. This vaccine has also been studied in men, who can develop cancer, RRP, and genital warts from HPV. In addition, men can transmit the virus to women, potentially causing cervical cancer in