A bivalent vaccine for human papillomavirus manufactured by GlaxoSmithKline has shown greater than 90% efficacy against high-grade cervical intraepithelial neoplasia, according to interim results from a large, randomized controlled trial published online in the Lancet.
The study, led by Dr. Jorma Paavonen and colleagues, is called the Papilloma Trial to Prevent Cervical Cancer in Young Adults (PATRICIA), and involves 18,644 women, aged 15–25 years, from 14 countries in Europe, Asia, and North America. The participants were randomly assigned to receive three injections of the human papillomavirus (HPV) vaccine or a hepatitis A vaccine at months 0, 1, and 6 (Lancet 2007; DOI:10.1016/S0140-6736[07]60946-5).
The study was sponsored by GlaxoSmithKline. Several study investigators were employees of the company, and others, including Dr. Paavonen of the University of Helsinki received consulting and lecture fees from the pharmaceutical firm.
The vaccine, Cervarix, has not yet been approved by the Food and Drug Administration. If it is approved, it will be competing against Merck's already released HPV vaccine, Gardasil. Cervarix is a bivalent vaccine, active against HPV types 16 and 18, which account for 70% of all cases of cervical cancer. Gardasil is a quadrivalent vaccine, active against HPV types 6 and 11 (the cause of 90% of genital warts) in addition to types 16 and 18.
In the current study, only 2 of the 9,319 women receiving Cervarix developed cervical intraepithelial neoplasia (CIN) of grade 2 or 3 and related to HPV 16 or 18, compared with 21 of the 9,325 women in the control group. This translates into an efficacy of 90%.
The vaccine also showed 89% efficacy against grade 1 or higher CIN.
Virtually all the women receiving the HPV vaccine (99.5%) had developed antibodies against HPV 16 and 18 after the second of the three injections.
In an accompanying editorial, Dr. Jessica A. Kahn of the University of Cincinnati and Dr. Robert D. Burk of the Albert Einstein College of Medicine, New York, described these results as “encouraging,” while sounding a note of caution (Lancet 2007; DOI:10.1016/S0140-6736[07]60947-7).
They noted that the follow-up time was only about 15 months, which is short compared with the several decades over which cervical cancer often evolves. The enrollment criteria in the trial were relatively narrow, so it's unknown whether seroconversion rates, antibody titers, and efficacy rates will be as high when the vaccine is distributed to a wider population.
Dr. Kahn and Dr. Burk also emphasized that the vaccine was not without side effects. Although generally well tolerated and safe, the HPV vaccine caused significantly more local adverse events such as pain, redness, and swelling, than did the hepatitis A vaccine. Risks of general adverse events, including arthralgia, fatigue, and myalgia, also were significantly higher in the HPV group.
Dr. Kahn and Dr. Burk stressed the need for the vaccine to be made available in less-developed regions of the world, where cervical cancer makes the largest contribution to years of life lost to cancer. “Poverty is strongly associated with high-risk HPV infection and cervical cancer,” they wrote. “If those who live in poverty cannot access highly effective interventions such as HPV vaccines, disparities could worsen dramatically.”