The proportion of young women diagnosed with genital warts in Australia has seen a significant decline thanks to the HPV vaccine, suggests a new paper.
In 2007, Australia became one of the first countries to implement a nationally funded quadrivalent human papillomarivus (HPV) vaccination programme for girls and young women, which offers free vaccinations to girls aged 12-13 years in schools. From 2007 -- 2009 there were a further two catch-up programmes: for 13-18 year olds and 18-26 year olds. The vaccine protects against the types of HPV that cause 90% of genital warts, as well as the cancer-causing HPV types.
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.
Researchers from the University of New South Wales and Melbourne Sexual Health Centre therefore looked to describe the ongoing population effect of the vaccination programme, five years after it was established.
Data were taken 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.
The study 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 dramatically to 0.85% (13 cases altogether).
In 2011, none of the vaccinated women under 21 were diagnosed with genital warts. In the same year, 7% of unvaccinated women under 21 (out of 161) were diagnosed with genital warts.
Significant 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. They hope that this trend will be mirrored in the UK which will help reduce the workload in sexual health clinics but say it is also important to vaccinate boys. They say these are "exciting times in the science of HPV" and we can look forward to the "virtual elimination of genital warts […] most genital cancers and some 60% of head and neck cancers."
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