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High efficacy is predicted for pair of new human papillomavirus vaccines.

JACKSONVILLE, FLA. -- Both vaccines to prevent human papillomavirus infection will be highly effective, Dr. Diane M. Harper said at a conference on STD prevention sponsored by the Centers for Disease Control and Prevention.

Approximately 600 women participated in efficacy studies for a quadrivalent vaccine (Gardasil, Merck), and another 1,100 participated in efficacy studies for a bivalent vaccine (Cervarix, GlaxoSmithKline).

All women were screened at baseline to ensure seronegativity for high-risk strains 16 and 18 of the human papillomavirus (HPV) as well as for strains 6 and 11, which are also included in the quadrivalent product.

"The response was 100% for the bivalent and 89% for the quadrivalent for persistent, vaccine-specific HPV types for those who got the vaccine on time," Dr. Harper said. The recommended regimen for both vaccines is a 0.5-cc injection at 0, 2, and 6 months. In the studies, 94% of participants received all three doses, although not all according to protocol. The off-schedule efficacy was 95% and 89%, respectively, but these differences were not statistically different. "It indicated these will work in a real-world setting," she added.

Goals of vaccination include reduction of HPV transmission and anogenital lesions, "but most importantly we want to reduce incidence of cervical cancer," said Dr. Harper, director of the Gynecologic Cancer Prevention Research Group at the Norris Cotton Cancer Center, Lebanon, N.H. She added that prevention of other anogenital cancers may be a serendipitous benefit of the vaccines. Licensure of the quadrivalent vaccine is expected soon, and the bivalent vaccine may be cleared for marketing by the end of this year.

Both vaccines target high-risk HPV type 16, the type primarily implicated in cervical cancer. Type 16, together with types 18 (also in both vaccines), 31, and 45, account for 81% of cervical cancers, Dr. Harper said. The bivalent vaccine, "although it was designed for 16 and 18, is just as efficacious for HPV 45 and half effective for HPV 31, so that is exciting," said Dr. Harper, who is also a professor of community and family medicine and obstetrics and gynecology at Dartmouth Medical School, Hanover, N.H. Dr. Harper was also a consultant for Merck and Glaxo-SmithKline and a researcher for the efficacy trials of each vaccine.

"These vaccines are preventive; they are not therapeutic--that is important to know," Dr. Harper said. "These prevent possible infection by HPV; these are not vaccines that prevent cancer." Because it is important that prevention lasts a long time, the need for a booster shot is anticipated with the bivalent vaccine 7-10 years later, Dr. Harper said. "We don't know if the quadrivalent vaccine will require a booster."

Researchers found high antibody titers at 7 months in the study participants who received all doses by 6 months. "This is the only disease other than infant influenza where you see higher titers from the vaccine than from the disease itself," Dr. Harper said.

Participants in the quadrivalent vaccine efficacy trials who reported prior exposure to HPV had antibody titers twice those of participants who were exposure naive. Dr. Harper said, "It's important to know that the vaccine works well in people previously exposed to HPV. It is good because women at all ages are at risk."

Adverse effects at local injection sites, including pain, erythema, and edema, were similar for both vaccines versus placebo. Other side effects such as headaches, gastrointestinal problems, and fatigue occurred at similar, "acceptable" rates in placebo and vaccine recipients, Dr. Harper said.

Other safety concerns with vaccines include new-onset autoimmune disease and musculoskeletal problems. "We can say no in both cases," she said.


Miami Bureau
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Author:McNamara, Damian
Publication:OB GYN News
Geographic Code:1USA
Date:Jun 1, 2006
Previous Article:HPV prevalence peaks in 14- to 19-year-old women.
Next Article:Updated STD guidelines from CDC coming soon.

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