Human Papilloma Virus Vaccine Effective In Women Aged 24-45 Not Previously Exposed

An article published Online First and in an upcoming edition of The Lancet reports that women aged between 24 and 45 can be protected by the human papilloma virus (HPV) vaccine, if they have not been already infected by the virus. The report is the work of Dr Nubia Muñoz, from the National Institute of Cancer, Bogotá, Colombia, and collaborators.

Over the last thirty years, sexual behavior has changed. The age of the first marriage is rising, divorce rates are augmenting. As a result, premarital intercourse and having a new sexual partner around middle-age are common behaviors. The HPV virus is transmitted through sexual intercourse and can lead to cervical cancer or other cervical disease. It could be beneficial for older women to receive vaccination against the HPV virus. The women who participated in the randomized trial did not have a history of cervical disease or cancer or genital warts, caused by HPV types 6, 11, 16 and 18. The first group of women received the quadrivalent HPV vaccine and the second group received placebo (at day 1 and months 2 and 6).

There were a total of 1911 women in the first group and 1908 in the second group. The first endpoint for assessment was infection for six months or more, and cervical and external genital disease due to HPV 6, 11, 16, 18. The second was the same but genital disease was due to HPV 16 and 18 only. The average of follow-up time was of 2.2 years. No further data was analyzed at the end of the four year trial. Among the women, specific populations were analyzed.

The per-protocol population of ideal participants included 1615 women who were given the vaccine and 1607 receiving placebo. From day 1 and up to month seven, they all tested negative for the appropriate vaccine HPV type. Within one year, they all had to receive three vaccine doses. They were required to have one or more follow-up visits after month seven. Research showed that there were four cases of infection or disease in the vaccine group compared to forty one in the placebo group. Researchers observed the vaccine proved to have 91 percent effectiveness against all four virus strains (the percent reduction in incidence rate in the vaccine group compared to the placebo group). In the evaluation of the HPV 16 and 18 only, four cases occurred in the vaccine group compared with 23 in the placebo group (vaccine efficiency of 83 percent). When women who had not been completely vaccinated and had already existing HPV infection were included in the analysis, vaccine efficacy against all four HPV types was lower (31 percent). Effectiveness was of 24 percent when it was specifically against types HPV 16 and 18.

The authors write: "Lower effectiveness (about 30%) detected in the mixed population (susceptible women and those who have already acquired HPV infection or HPV-associated disease) suggests that the public health effect of vaccinating women aged 25-45 years will be smaller than that recorded after vaccinating susceptible adolescents. This notion will be assessed in future cost-benefit analyses."

Although there were two target outcomes of the trial, the researchers observed that in general, the women reaching the endpoint had infections, rather than cervical or genital disease. As a result, the high vaccine efficacy in the intention-to-treat population was mostly as a result of efficacy against infection.

The authors explain: "Maximum effect from prophylactic HPV vaccination programmes will be achieved in women who are susceptible to infection and disease related to vaccine HPV types (those not previously exposed). Notably, most adult women enrolled in the current study remained susceptible to vaccine HPV types at entry. Almost all women enrolled were susceptible to three or four vaccine HPV types, and about a third were positive to HPV 6, 11, 16, or 18 at baseline by serological or DNA testing; therefore about two-thirds were susceptible to all four vaccine HPV types. Most women who were HPV positive were positive to only one HPV type, meaning that the quadrivalent HPV vaccine could still potentially benefit these women via protection against vaccine HPV types with which they are not infected with."

They write in conclusion: "The quadrivalent HPV vaccine is efficacious in women aged 24��"45 years not infected with the relevant HPV types at enrolment."

"Safety, immunogenicity, and efficacy of quadrivalent human papillomavirus (types 6, 11, 16, 18) recombinant vaccine in women aged 24-45 years: a randomised, double-blind trial"
Nubia Muñoz, Ricardo Manalastas Jr, Punee Pitisuttithum, Damrong Tresukosol, Joseph Monsonego, Kevin Ault, Christine Clavel, Joaquin Luna, Evan Myers, Sara Hood, Oliver Bautista, Janine Bryan, Frank J Taddeo, Mark T Esser, Scott Vuocolo, Richard M Haupt, Eliav Barr, Alfred Saah
DOI: 10.1016/S0140-6736(09)60691-7
thelancet

Written by Stephanie Brunner (B.A.)
Copyright: Medical News Today