MONTREAL — Uptake of the human papillomavirus vaccination is too slow, say some experts, while others still question whether enough is known about the risk-benefit ratio to deem the vaccination truly necessary.
In an industry-sponsored symposium held during the meeting, Dr. William Fisher, a consultant to Merck, strongly urged physicians to make HPV vaccination a routine part of their practice.
There are about 100 strains of HPV virus, with 15 considered oncogenic. HPV strains 16 and 18 are responsible for about 70% of cervical cancer, while strains 6 and 11 are responsible for genital warts. Merck's Gardasil vaccine targets all four strains, while Cervarix (GlaxoSmithKline PLC) targets the oncogenic strains 16 and 18.
“HPV vaccine would seem to be a very reasonable form of protection, for both men and women, who may be sexually active in an environment characterized by a very high level of HPV,” as the infection may have serious health consequences for the individual and his or her partner, said Dr. Fisher, a professor in the departments of psychology and obstetrics and gynecology at the University of Western Ontario, London.
To illustrate the prevalence of HPV infection, Dr. Fisher noted a 25% rate of infection with high-risk oncogenic strains of HPV among Canadian teenage girls, aged 15-19 years, in a low-risk family practice setting who were negative for HPV the previous year (CMAJ 2003;168:421-5).
Similarly, among a group of 621 university-age women tested every 6 months for 2 years, the rate of newly acquired high- and low-risk HPV strains was 13% at 1 year, and 29% and 24%, respectively, at 2 years (Cancer Epidemiol. Biomarkers Prev. 2003;12:485-90).
“We couldn't be talking more clearly about a sociosexual epidemic,” he said. “This is a social disease on steroids,” said Dr. Fisher, who is also a research affiliate at the Center for Health, Intervention, and Prevention at the University of Connecticut, in Storrs.
In a recent study involving young Canadian couples, HPV was present in 64% of new couples and the oncogenic HPV-16 strain was the most common strain found at baseline.
Concordance of strains was 41% at baseline and grew to 68% at 6 months, he said (Epidemiology 2010;21:31-7). “There's no doubt in new relationships that HPV is rapidly becoming part of the sociocultural landscape,” Dr. Fisher said.
While there is a well-established link between high-risk HPV and gynecologic cancers, HPV-related head and neck cancers are “probably the newest sexually transmitted infections on the radar,” he said.
A recent study shows that in Sweden the prevalence of oncogenic HPV strains in head and neck cancer biopsies has increased from 23% in the 1970s to 77% by 2005 (Int. J. Cancer 2009;125:362-6).
In addition, a study from this year shows that the risk of HPV-related head and neck cancer, while increased with six or more coital partners (odds ratio 1.25), more than triples with more than four oral-genital partners (OR 3.36). “Oral-genital sex is the new handshake, and it is actually likely that people have more oral-genital partners than coital partners,” Dr. Fisher added.
Yet while Canadian and U.S. authorities recommend HPV vaccination in young girls and women, and school-based vaccination programs are offered across Canada, such recommendations have not resulted in mass vaccination, he said. A recent study suggests that only about one-third of American girls, aged 13-17 years, have been vaccinated (Am. J. Prev. Med. 2010;38:525-33).
Dr. Marie Plante, president of the Society of Gynecologic Oncologists of Canada, said that as a gynecologic oncologist she sees the downside of such low vaccination rates. “We treat women with cervical cancer…. I've got several of them in their 20s and early 30s and it ruins their lives, and they can't have children sometimes. So we see the frustrating part because it could have been prevented,” said Dr. Plante, associate professor of obstetrics and gynecology, and chief of the gynecologic oncology division at Laval University in Quebec City. She estimates that about 50% of cervical cancer cases she sees are in women whose regular screening had failed to identify it.
“As much as I am very critical of the push from the companies [to market their vaccines], I will tell you that honestly I think the vaccine is safe,” Dr. Plante continued. Is it necessary? “No, it is not necessary,” she said. “It doesn't guarantee 100% protection. It's an option you have to reduce the chances that you develop precancerous cells. In most cases this will be treated quickly and won't take your life away.” Importantly, the vaccine also reduces the potentially significant burden of genital warts, the experience of which is “amazingly negative”—it's “terrible and painful,” she added.