Writing in the lead article of this week's issue of The Lancet, Harper and her fellow authors said the vaccine has the potential to greatly reduce deaths from cervical cancer, one of the leading causes of cancer mortality among women worldwide. The vaccine is targeted to immunize against two different types of high risk Human Papillomavirus (HPV-16 and HPV-18) that cause an estimated 70 percent of cervical cancer cases.
HPV is a commonly occurring infection, transmitted by skin to skin contact, most commonly through normal sexual interactions. Although most cases of HPV resolve themselves through natural immunity, a percentage of cases will progress to cervical cancer. Currently, an estimated 280,000 women die from cervical cancer each year, most of them in the developing world. Of the 500,000 cases of cervical cancer diagnosed annually, 70 percent are attributed to infection from HPV-16 and18. The five year prevalence of cervical cancer worldwide - in other words, the number of women in any five year period of time with cervical cancer - is 1.4 million.
In the blinded, randomized trial of 1,113 women from throughout the U.S., Canada, and Brazil, participants received 3 doses of the experimental vaccine or a placebo over 6 months. At 27 months of follow-up, the vaccine showed an extremely high rate of efficacy, the authors write. In those women who completed the protocol - receiving all three shots and participating in all scheduled testing and follow-up - the vaccine was 100 percent effective against persistent HPV16/18 infections.
Significantly, the efficacy was only slightly reduced for those women who did not fully comply with the protocol - receiving only one or two of the 3 shots or not completing all scheduled follow-up appointments. In that group, the vaccine proved 95 percent effective against persistent HPV infection and 93 percent against cytologic abnormalities associated with HPV 16/18, and complete protection from cervical tissue changes due to HPV16/18.
Harper, a clinician who actively treats women in the Obstetrics and Gynecology section at DHMC, as well as a researcher, is internationally recognized for her pioneering work on HPV. She called the results of the study "extremely exciting and encouraging. We believe this shows enormous potential to eradicate the great majority of cervical cancers worldwide."
Harper noted that while other vaccines against HPV are currently being tested, this trial is notable because it is the first to target two viruses with one vaccine. "Our trial results showed a high degree of safety, with no adverse effects to the participants, and highly significant and complete protection against persistent infection. This has enormous implications for women worldwide, and for our health system, which annually spends billions of dollars on cervical screening programs."
Recruitment for a larger, Phase III trial of the vaccine - the last step prior to licensing the drug for general use - is now underway at Norris Cotton Cancer Center and other sites, Harper said. "We hope these results will encourage women to sign up for this trial." She noted that Norris Cotton Cancer Center is the only Northeastern site other than Philadelphia participating in the large-scale trial, so women from throughout New England who meet the criteria and are interested are advised to enroll here. For more information on the trial, email vaccine@Dartmouth.edu or call Lisa Matthews at 603-653-3692.
The vaccine discussed in The Lancet article and in the larger trial now underway is being developed and would ultimately be licensed by GlaxoSmithKline. Dr. Harper is an independent researcher who acted as Primary Investigator and is neither paid nor employed by GSK.
Norris Cotton Cancer Center is a premier cancer research, education, and treatment facility that combines advanced cancer research at Dartmouth Medical School with compassionate care at Dartmouth-Hitchcock Medical Center. Designated as one of a select group of Comprehensive Cancer Centers by the National Cancer Institute (NCI), it is also ranked one of the top cancer facilities in America by U.S. News & World Report.