WEDNESDAY, April 6, 2005 (HealthDay News) -- A vaccine against human papillomavirus (HPV), the cause of cervical cancer and genital warts, dramatically cut the infection rate for both by 90 percent in a small-scale trial, researchers report.
The vaccine, made by the drug company Merck & Co., is one of two HVP vaccines involved in a race toward approval. But they differ in the range of protection they offer.
A vaccine made by GlaxoSmithKline proved in a small trial reported last fall that it protects against HPV16 and HPV18, the two types mainly responsible for cervical cancer.
The Merck vaccine protects against HPV16 and HPV18, and also against HPV6 and HPV11, the two types responsible for genital warts, according to study results published online in the April 7 issue of Lancet Oncology.
The new trial involved 1,158 healthy women aged 16 to 23 who were recruited from Brazil, Europe and the United States. Luisa Villa of the Ludwig Institute for Cancer Research in Sao Paulo, Brazil, and colleagues assigned the vaccine randomly to 277 women; 275 others were given a placebo. The participants were followed for 36 months.
And, the researchers reported, the "combined incidence of persistent infection or disease with HPV6, 11, 16, or 18 fell by 90 percent in those assigned vaccine compared with those assigned placebo." The vaccine was also 100 percent effective against precancerous cervical lesions and genital warts associated with the four HPV types.
Both vaccines now are in much larger trials designed to lead to approval for general clinical use in the United States and abroad, said Dr. Mark H. Stoler, a professor of pathology and gynecology at the University of Virginia School of Medicine and an author of the report in Lancet Oncology.
The Merck trial will include more than 18,000 women, with results expected in two to three years, Stoler said. A similar-sized GlaxoSmithKline trial is running on roughly the same schedule.
There is room for both vaccines, and even more, said Dr. Darron R. Brown, a professor of medicine, microbiology and immunology at the Indiana University School of Medicine and another author of the report.
"The burden of HPV disease is so wide that even a third or fourth vaccine would be welcome," Brown said. "Cervical cancer is the No. 2 cancer killer of women worldwide, and the No. 1 killer in undeveloped countries."
And even though routine screening with the Pap test has greatly reduced the cervical cancer toll in the United States, "we have as many as 15,000 new cases and 5,000 cervical cancer deaths each year," Brown said.
"A lot of those cases occur in women who have never had a Pap smear or have not had one in the past five years. A vaccine would work to protect them," he added.
But regulatory approval of any HPV vaccine would raise a number of medical, economic and social issues, Stoler said. HPV is sexually transmitted, he noted, and so "people must be vaccinated before they are exposed, which means before they are sexually active."
For a vaccination program to be effective, "parents would have to come around to the concept that their children need to be vaccinated for a sexually transmitted disease," he said.
Cost would be a major issue in less-developed countries, Stoler added. "The vaccine will be efficacious and scientifically sound, but it probably is not going to be cheap," he said, especially in countries where overall health-care spending is in the neighborhood of about $1 a day.
Brown is more optimistic. "Once we show that the vaccine works, a lot of countries will see the long-term economic benefit of reducing cervical cancer," he said.
"My optimistic assessment is that in two years we will have a vaccine available," he added.
More information
Everything you need to know about cervical cancer is available from the National Cancer Institute.
