Quadrivalent HPV Vaccine (Gardasil) Cuts Rates of Genital Warts

From Medscape Medical News
Roxanne Nelson

October 21, 2009 — The quadrivalent human papillomavirus (HPV) vaccine (Gardasil, Merck & Co) can reduce the incidence of genital warts in women and girls, and might even benefit heterosexual men. According to Australian researchers, the proportion of young women diagnosed with genital warts declined by 25% each quarter in 2008 after the initiation of an HPV vaccine program.

This is in comparison to a 1.8% increase in new cases of genital warts per quarter from 2004 to 2007, before the beginning of the vaccination initiative. The results of this analysis were published online October 16 in Sexually Transmitted Infections.

The main aim of HPV vaccination is to reduce cervical cancer (caused by HPV types 16 and 18), but Gardasil, 1 of the 2 vaccines that is available, also offers protection against genital warts (HPV types 6 and 11); Cervarix (GlaxoSmithKline), the other one, does not.

The authors note that governments in different countries are currently trying to decide which of the 2 vaccines should be included in their immunization programs, and need robust data to determine the impact of the vaccine at a population level. Beginning in 2007, Australia became one of the first countries to offer the Gardasil vaccine free of charge to girls aged 12 to 18 years, in a school-based program, and to women younger than 27 years, through general practices. The coverage rate for women between 18 and 26 years is estimated to be 65% to 70%.

Although both vaccines are licensed in Australia, only Gardasil is being used in the program. "Gardasil is the only free one at this stage," lead author Christopher K. Fairley, MBBS, PhD, told Medscape Oncology. "But one can buy Cervarix privately."

There are also no programs targeting men at this point. "It is licensed for boys, but must be purchased privately," said Dr. Fairley, who is a professor of sexual health at the University of Melbourne and director of the Melbourne Sexual Health Centre (MSHC) in Australia.

Reduced Incidence of Warts in Targeted Population

The goals of the study were to evaluate the national HPV vaccination program and to determine if it had a measurable impact on the clinical presentation of genital warts in the year after its implementation.

In this retrospective study, Dr. Fairley and colleagues compared the proportion of new patients who were diagnosed with genital warts at the MSHC from January 2004 to December 2008. During that time, 36,055 patients were seen at MSHC for the first time, and genital warts were diagnosed in 3826 (10.6%).

Only women younger than 28 years showed strong evidence of a significant difference in the average quarterly change between time periods; there was a 1.8% increase before the end of 2007 and a 25.1% decrease after the end of 2007 (P < .001). Heterosexual men were the only other subgroup to show a decrease in presentations for genital warts in 2008, with an average quarterly decrease of 5% (P = .031).

No reduction was seen in homosexual men or women beyond the targeted age group (>28 years).

The reduction in genital warts observed in heterosexual but not homosexual men might be consistent with a reduction in heterosexual transmission of HPV as a result of the women's vaccine program, the authors write. "These data should be of value to governments making decisions about whether to implement HPV vaccination in women and may assist in informing the choice of vaccine," they conclude.

Dr. Fairley pointed out that, when determining the cost effectiveness of vaccination, the avoided costs must be taken into account as well as the actual cost of the vaccine, if the price between them differs.

"There is also the issue of the duration of the immune response, and whether other subtypes are covered," he said. "Both these issues are currently under debate by the 2 vaccine companies."

No funding was obtained to undertake this study. Dr. Fairley reports receiving honoraria and research funding from and owns shares in CSL Biotherapies, the manufacturer of Gardasil. Coauthor Jane S. Hocking, MPH, PhD, from the University of Melbourne, reports receiving honoraria from CSL Biotherapies. Coauthor Basil Donovan, MD, from the University of New South Wales in Australia, reports receiving research funding from CSL Biotherapies and honoraria from GlaxoSmithKline and CSL Biotherapies.

Sex Transm Infect. Published online October 16, 2009. Abstract