Nov. 8, 2010 – Australia's campaign to vaccinate girls and young women against the human papillomavirus (HPV) has cut genital warts cases by about 60% in young women -- and by almost 30% in heterosexual men.
The HPV vaccine used in Australia is Gardasil, developed by CSL Biotherapeutics in Australia and licensed to the U.S. firm Merck. Gardasil is a four-way vaccine that protects against the two HPV strains that cause most cervical cancers as well as the two HPV strains that cause most genital warts.
In 2007, Australia launched a school-based vaccination campaign for all girls ages 12 to 16 and a catch-up program for all women up to age 26. The three-shot vaccination was free, and nearly two-thirds of young Australian women received the Gardasil vaccine.
Now a survey of more than 112,000 people attending Australian sexual health services finds that genital warts cases have dropped substantially since the vaccination program -- but not for everyone:
- Genital warts cases dropped by 59% in women under age 26 at the time of the vaccination program.
- Genital warts cases dropped by 28% in exclusively heterosexual men, especially among young men.
- Genital warts cases did not decline in women too old to be included in the vaccination program.
- Genital warts cases did not decline in men who had sex with other men.
- Genital warts cases did not drop in non-resident women living in Australia.
Gardasil for Girls: Male Protection, Too?
Why were men protected? The Australian vaccination program offered free Gardasil to females, but males had to pay. As a result, fewer than 5% of Australian men have been vaccinated.
Only exclusively heterosexual men saw some protection. Vaccination of young women resulted in enough "herd immunity" to reduce, but not eliminate, HPV spread among men, suggests study leader Basil Donovan, MD, professor of sexual health at the University of New South Wales, Sydney, Australia.
Donovan and colleagues note that HPV can cause anal cancer and may aid the spread of HIV, the AIDS virus. For these reasons, they suggest that future HPV prevention programs should consider vaccinating males as well as females.
The fact that genital warts cases did not decline further may be due to the half-million "backpackers" -- young people who visit Australia each year, says Donovan.
Many of these young visitors have been vaccinated against HPV, but a significant proportion of those women may have received the GlaxoSmithKline's Cervarix HPV vaccine. Like Gardasil, Cervarix protects against the two HPV strains that cause most cases of cervical cancer. But unlike Gardasil, Cervarix does not protect against the two HPV strains that cause most genital warts.
The U.S. FDA has approved both Cervarix and Gardasil, and either is recommended for young women. The U.S. Vaccines for Children Program pays for Gardasil vaccination for boys as well as for girls, even though the vaccine is not specifically recommended for males. Such a recommendation is under consideration by the U.S. Advisory Committee on Immunization Practices, an expert panel that sets U.S. vaccination policy.
The Donovan study appears in the Nov. 9 online edition of The Lancet.