A vaccine against two high-risk types of human papillomavirus (HPV) reduced the risk of precancerous cervical changes in young women. These results were published in The Lancet.
Human papillomaviruses consist of more than 100 different viruses. Some types of HPV cause warts on the hands or feet; others cause genital warts; and some have been linked with cancer, most notably cervical cancer. The types of HPV most commonly linked with cervical cancer are HPV16 and HPV18, but several other high-risk types contribute to cancer as well.
The types of HPV that cause cervical cancer or genital warts are transmitted sexually. HPV infection is extremely common and generally occurs soon after an individual becomes sexually active. Although most infections resolve on their own, some persist and can lead to precancerous or cancerous changes to the cervix, vulva, vagina, penis, and anus. HPV infection has also been linked to certain cancers of the head and neck.
Recognition of the link between HPV and cervical cancer led to the development of vaccines designed to prevent infection with certain high-risk types of HPV. Gardasil® targets HPV types 6 and 11 (which are linked with genital warts) as well as the cancer-associated types 16 and 18. Gardasil was approved by the U.S. Food and Drug Administration (FDA) in June 2006. Cervarix targets HPV types 16 and 18 only. Cervarix has not yet been approved in the United States, but has been approved in many other countries. A potential advantage of Cervarix is that it uses a new type of adjuvant (a substance added to increase immune response); this may boost the strength or duration of vaccine protection.
The PATRICIA trial (PApilloma TRIal against Cancer In young Adults) is a Phase III clinical trial that evaluated the efficacy of Cervarix against precancerous changes to the cervix (cervical intraepithelial neoplasia 2 or worse). The study enrolled more than 18,000 women between the ages of 15 and 25 years. Roughly half of the women were assigned to receive Cervarix. The vaccine was given in three doses over a six-month period.
Study participants have now been followed for an average of almost three years.
Vaccine efficacy against precancerous cervical changes due to HPV16 or HPV18 was 93%.
Vaccine efficacy against precancerous cervical changes due to 12 other high-risk types of HPV (HPV types not included in the vaccine) was estimated to be between 37% and 54%. This was mainly the result of cross-protection against HPV31, HPV33, and HPV45.
This study suggests that Cervarix is highly effective at preventing HPV16- and HPV18-related precancerous cervical changes. Cervarix also appears to offer some degree of cross-protection against three other high-risk types of HPV.
Reference: Paavonen J, Naud P, Salmeron J et al. Efficacy of human papillomavirus (HPV)-16/18 AS04-adjuvanted vaccine against cervical infection and precancer caused by oncogenic HPV types (PATRICIA): final analysis of a double-blind, randomized study in young women. Lancet [early online publication]. July 7, 2009.