My primary concern about the commentary on human papillomavirus (HPV) vaccine Gardasil by Abby Lippman and colleagues (1) is that the full burden of disease prevented by Gardasil is overlooked. Clinical trials have shown that the quadrivalent HPV vaccine is 96%-100% effective at preventing infections from the HPV types that cause the most diseases: types 6, 11, 16 and 18. These HPV types are responsible for more than 90% of genital warts, about 70% of cervical and anogenital cancers and high-grade precancers, and 35%-50% of low-grade cervical, vaginal and vulvar lesions. All 4 types cause abnormal Papanicolaou smear results. Recent data on cross-protection have shown that Gardasil offers additional protection against 10 cancer-causing HPV types not included in the vaccine. (2)
HPV infections annually lead to about 400 000 abnormal Pap smear results, 85 000 consultations because of genital warts and 36 000 new cases of genital warts, as well as 1400 cervical cancer diagnoses and 400 cervical cancer deaths. (3) HPV is also linked to other cancers in both men and women, such as cancers of the penis, anus, vagina and vulva, as well as loss of female fertility. Moreover, HPV in the oral cavity is associated with an increased risk of laryngeal papillomatosis (4) and head and neck cancers. (5)
Regarding the efficacy of Pap smear testing at preventing cervical cancer, according to a 1998 surveillance report published by the Public Health Agency of Canada, about 40% of cervical cancer cases were found in women screened within the previous 3 years. (6) Pap smear testing is also woefully inadequate for those women most likely to develop cervical cancer, namely, those who are poor, poorly educated or marginalized.
Despite incredible advances in communication over the last 20 years and a vast improvement in Pap smear screening programs, our ability to further reduce the incidence and prevalence of cervical cancer has stalled. The incidence and prevalence of genital warts in Canada have also been on the rise over the past 20 years, which seems to indicate that current preventive measures are insufficient. Immunization with the quadrivalent HPV vaccine, coupled with proper education, continued Pap smear testing and ongoing post-vaccination surveillance, is the new standard of care in Canada.
James A. Mansi PhD
Medical & Scientific Affairs for Vaccines
Merck Frosst Canada
Competing interests: James Mansi is an employee and stockholder of Merck Frosst Canada.
(1.) Lippman A, Melnychuk R, Shimmin C, et al. Human papillomavirus, vaccines and women's health: questions and cautions. CMAJ2007;177:484-7.
(2.) Brown D. HPV type 6/11/16/18 vaccine: first analysis of cross-protection against persistent infection, cervical intraepithelial neoplasia (CIN), and adenocarcinoma in situ (AIS) caused by oncogenic HPV types in addition to 16/18. Presented at the 47th Annual Interscience Conference on Antimicrobial Agents and Chemotherapy; 2007 Sep 17-20; Chicago (IL).
(3.) Brisson M. The health and economic burden of HPV infection, genital warts, cervical dysplasia and cervical cancer in Canada [presentation]. Presented at the 7th Canadian Immunization Conference; 2006 Dec 3; Winnipeg (MB). Available: www.phacaspc. gc.ca/cnic-ccni/2006/pres/_pdf-sun-dim-dec03 /4-Hall-B-Viral-Diseases-and-Vaccines/Brisson_BOIHPV_...