Six years into a successful human papillomavirus (HPV) vaccination campaign, with 83% first-dose coverage, Australia has experienced a 92.6% decline in new genital warts cases among girls younger than 21 years, according to a study published online April 18 in BMJ.
Collating data for 85,770 new patients seen at 8 sexual health centers for the first time, Hammad Ali, MD, from the University of New South Wales in Sydney, Australia, and colleagues found that the proportion of women younger than 21 years who were diagnosed with genital warts plummeted from 11.5% in 2007 to 0.85% in 2011.
As a result of the publicly funded vaccination program, which was implemented among Australian schoolgirls aged 12 to 13 years in 2007 (with a 2-year catch-up program for those aged 13 to 26 years), only 13 new cases of genital warts were reported among this age group in 2011 (pre/postvaccination rate ratio, 0.64; P < .001).
Notably, none of 235 vaccinated women younger than 21 years were found to have genital warts in 2011, and the rate was also reduced among their unvaccinated counterparts relative to 2006 (7.3% vs 10.5%). Early data also show a significant decrease in the rate of high-grade cervical abnormalities, which can presage cancer, among girls younger than 18 years.
Among women aged 21 to 30 years, the effect was attenuated by lower vaccination coverage, but HPV diagnosis rates still declined 72.6%, going from 11.3% in 2007 to 3.1% in 2011 (pre/post ratio, 0.81; P < .001).
Heterosexual males also benefited from female vaccination: An 81.8% decline in new genital warts cases was observed among males younger than 21 years ((decline from 12.1% to 2.2%; pre/post ratio, 0.72; P < .001), and a 51.1% drop occurred among those aged 21 to 30 years (decline from 18.2% to 8.9%; pre/post ratio, 0.88; P < .001).
"The decline in genital warts in the two younger age groups of heterosexual men can most likely be attributed to herd immunity, which is the indirect protection that unvaccinated people enjoy as a result of reduced exposure to infection," the authors write, noting that the free vaccination program has been expanded in 2013 to cover 12- to 13-year old boys (with a 2-year catch-up program for 14- to 15-year-olds) in an effort to eradicate HPV as much as possible.
"These are exciting times in the science of HPV and the world can confidently look forward to the virtual elimination of genital warts, recurrent laryngeal papilloma, most genital cancers, and some 60% of head and neck cancers," Simon Barton, MD, from the Chelsea and Westminster Foundation Trust in London, United Kingdom, and Colm O'Mahony, MD, from the Countess of Chester Trust in Chester, United Kingdom, write in an accompanying editorial.
'Fear Trumps Science' for Many Americans
According to the study authors, HPV vaccination was widely accepted in Australia: In 2010, 83% of 12- to 13-year-old girls had received 1 dose, 80% had received 2 doses, and 73% had completed the 3-dose vaccination regimen.
In contrast, HPV vaccination rates among American schoolgirls remain abysmal. As previously reported by Medscape Medical News, only 32.0% of American girls aged 13 to 17 years in 2010 had received all 3 doses.
According to Marc Tanenbaum, MD, a pediatrician based in Atlanta, Georgia, the problem rests squarely on the shoulders of squeamish parents.
"I still find myself remarkably challenged to convince the parents of my patients to allow their 11- and 12-year[-old] children, girls and boys, to get this important vaccine," Dr. Tanenbaum told Medscape Medical News, noting that despite clear evidence to the contrary, many parents are convinced that vaccination confers a license for promiscuity, and therefore prefer to wait until the child is older, when antibody response may be suboptimal.
"I once heard a lecturer say about scientific evidence of medical safety and benefit that 'fear trumps science,' " Dr. Tanenbaum quipped.
"It also amazes me that almost all parents think they will know or be told by their adolescent that he or she is planning to have their first sexual intercourse before the act, and that therefore there will be time to get the vaccine to protect their child. I think that most adults, parent or not, will hope that this would be true, but know in their hearts this would be unlikely and probably not reality," Dr. Tanenbaum added.
He urges all clinicians to continue informing and educating parents about the value and benefits of vaccinations.
"We ask our children to use car seat belts not only to keep them safe at the time but also in the hope that they will continue to do so when they are mature drivers. We do not think to suggest that introducing seat belt use as children is more likely to make them unsafe mature drivers. We do not wait until our children are drivers to require seat belt use on the theory that this delay will make them safer drivers when they are licensed. No doubt...a car accident involving an unbelted child will increase the child's motivation to use seatbelts when they grow up to drive a vehicle, but not without the risk of serious injury or death from that initial motor vehicle accident," Dr. Tanenbaum said.
"I would hope that all parents might take that orientation to permitting HPV immunization of their preteens, and not prefer to wait until they are older and are "driving with (or without) a license," Dr. Tanenbaum concluded.
The study was supported by CSL Biotherapies; CSL markets Gardasil (Merck) in Australia. One coauthor has disclosed relationships with CSL Biotherapies, Sanofi Pasteur, and Merck, and various other coauthors have disclosed relationships with CSL Biotherapies, Sanofi Pasteur MSD, Merck, and the Australian Advisory Board for the Gardasil HPV vaccine. The editorialists have disclosed relationships with GlaxoSmithKline and Sanofi Pasteur MSD. Dr. Tanenbaum has disclosed no relevant financial relationships.
BMJ. Published online April 18, 2013. Article full text, Editorial full text
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Cite this: HPV Vaccine Works, but Many American Parents Still Squeamish - Medscape - Apr 23, 2013.
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