Genital warts prevalence in Australian women plummeted 59% since a nationally funded quadrivalent human papillomarivus (HPV) vaccination program
for teen and pre-teen girls was introduced in 2007, says a paper in BMJ.
They made their determination by looking at statistics from eight sexual health services across Australia. Australian-born patients who attended any of the services for the first time between January 2004 and December 2011 were included in the analysis. In 2007, Australia implemented the HPV vaccination program for girls aged 12-13 years. From 2007–2009 there were a further two catch-up programs, for 13-18 year olds and 18-26 year olds. The vaccine protects against the types of HPV that cause 90% of genital warts and 70% of the the cancer-causing HPV types.
Their early data suggest two years after the vaccine was introduced, the proportion of genital warts diagnoses declined by 59% in vaccine eligible women aged 12-26 years and by 39% in heterosexual men. In the same two year period, there was a significant decrease in the incidence of high-grade cervical abnormalities in females under 18 years.
The analysis period was divided into the pre-vaccination period (2004-2007) and the vaccination period (2007-2011). The findings were also separated into three age groups: those under 21, 21-30 year olds and those 30 and older.
Between 2004 and 2011, 85,770 patients were seen for the first time. Of these, 7686 (9%) were diagnosed with genital warts. Overall, the proportion of women diagnosed with genital warts increased during the pre-vaccination period from 9% in 2004 to 10% in 2007, which then decreased in the vaccination period to 3%. In men the proportion remained relatively stable in the pre-vaccination period from 13% in 2004 to 12% in 2007 and then decreased during the vaccination period to 7%.
In women under 21, results showed that 9% were diagnosed with genital warts in 2004 and 11% in 2007. During the vaccination period the proportion declined to 0.85%m 13 cases altogether. In 2011, none of the vaccinated women under 21 were diagnosed with genital warts. In the same year, 7% of un-vaccinated women under 21 (out of 161) were diagnosed with genital warts.
Declines in genital warts were also seen in women aged 21-30 and heterosexual men under 21 and aged 21-30 years, during the vaccination period.
No significant trends were seen in women or heterosexual men over the age of 30.
The authors say this result in men is probably due to herd-immunity (immunity that occurs when the vaccination of a portion of the population provides a measure of protection for individuals who have not developed immunity).
In an accompanying editorial, Clinical Director Simon Barton and Sexual Health and HIV Consultant Colm O'Mahony say that it is "worth celebrating the extraordinary success" of this public health achievement, adding that it will probably have a major impact on the cost of sexual healthcare. In this week's BMJ podcast, a researcher also talks about the HPV vaccination and the paper's findings, noting the fact that there were no cases of genital warts in 2011 was "striking".