Genital wart incidence declined more than 90% among adolescent and teen girls in the four to five years after the HPV vaccine became available in Australia, researchers found.
Prevalence also declined 72.6% among an older cohort of women aged 21 to 30, and 50% to 80% among heterosexual boys and young men, compared with genital wart incidence in the three to four years prior to vaccine introduction.
Despite these improvements, there was no decline in wart frequency among heterosexual women or men aged older than 30 years, Basil Donovan, MD, of the Kirby Institute at the University of New South Wales in Sydney, Australia, and colleagues reported in the British Medical Journal (BMJ).
On a postive note, among the 235 female study participants younger than 21 years who reported previously receiving the HPV vaccine, there were no genital wart diagnoses in 2011.
“The significant declines in the proportion of young women found to have genital warts and the absence of genital warts in vaccinated women in 2011 suggests that the human papillomavirus vaccine has high efficacy outside the trial setting,” the researchers wrote. “Large declines in diagnoses of genital warts in heterosexual men are probably due to herd immunity.”
In 2007 Australia introduced it’s first nationwide HPV vaccination campaign for girls and young women, providing free in-school quadrivalent HPV vaccine to those aged 12 to 13 years. It also instituted a catch-up vaccination program for those aged 13 to 26 years. In 2011, vaccination coverage rates averaged nearly 80% for all three doses of HPV vaccine.
Initial reports from a surveillance network the first two years after the vaccine was introduced showed a 59% reduction in wart incidence among vaccine-eligible women aged 12 to 26 years, and a 39% decrease among heterosexual men of the same age. To get a better understanding of the population effects of the immunization program, Donovan and colleagues analyzed data from 2007 to 2011.
A total of 85,770 Australians visited one of eight sexual health clinics from 2004 to 2011, and accounted for 7,686 newly diagnosed genital wart cases — or about 9%, the researchers found.
From 2004 to 2007, the proportion of women with genital warts increased slightly from 8.9% to 9.6% and then fell to 2.7% in 2011. Among men, HPV prevalence declined from 12.8% to 11.7% in the first three years, and then fell to 7.4% in 2011.
The largest declines were observed among women younger than 21 years, with genital wart incidence decreasing from a peak of 11.5% in 2007 to 0.85% in 2011 — a 92.6% (P<0.001) reduction — the researchers found.
In an accompanying editorial, Simon Barton, MD, of the Chelsea and Westminster Foundation Trust in London, and Colm O’Mahony, MD, of the Countess of Chester Trust in Chester, England, said the findings were “worth celebrating,” and noted the “remarkable reduction” in genital wart incidence “will probably have a major impact on the costs of sexual healthcare.”
“Countries should consider these data seriously and act decisively,” they wrote.
It is likely that other places with national vaccination programs will see similar reductions in HPV-16 and HPV-18 associated diseases, including cervical cancer, vulval cancer, other anogenital cancers and head and neck tumours. Future efforts should focus on including boys and men in HPV immunization campaigns, and developing vaccines against HPV types 31 and 45, which have also been implicated in genital cancer.