• 4/7/2005
  • Rita Rubin
  • USA Today (www.usatoday.com)

A vaccine against the virus that causes cervical cancer and genital warts cut long-lasting infection by 90%, according to a pilot study out Wednesday.

Study co-author Eliav Barr of Merck Research Laboratories says his company expects to apply to the Food and Drug Administration late this year for permission to sell the vaccine, which would be the first against cancer.

Merck is now testing the vaccine in more than 25,000 women and children, up to one-third of them in the USA, in an expanded trial whose findings will be submitted to the FDA, Barr says.

Up to 70% of sexually active women will become infected with human papillomavirus, or HPV, during their lifetime, Barr and his collaborators write in an article posted online by The Lancet Oncology, a British medical journal. More than 90% of cases clear up on their own.

More than 35 types of HPV infect the genital tract, but four dominate, according to the article, the first about a vaccine against all four dominant types.

Two types, 16 and 18, are linked to 70% of cases of cervical cancer, diagnosed in 470,000 women worldwide each year but rare in the U.S., thanks to widespread screening. These types are also linked to less common cancers: About 80% of cancers of the anus or vulva are associated with HPV 16, and about half of penile cancers are linked to either 16 or 18, says Luisa Villa, lead study author and biologist with the Ludwig Institute for Cancer Research in Sao Paulo, Brazil.

The other HPV types targeted by the vaccine, 6 and 11, are associated with 90% of cases of genital warts, diagnosed in up to 1 million Americans each year.

The HPV vaccine contains genetically engineered particles that are nearly identical to the outer coats of the four types. Researchers randomly assigned 277 young women to get the vaccine, 275 to get a placebo. To ensure a hearty immune response, they received three shots over six months.

For three years, the women received regular pelvic exams, Pap smears and testing for antibodies to the HPV strains. Antibody levels dropped by the end of the study in the vaccine group, but they were still higher than those seen in women naturally infected with HPV.

No one who received the vaccine developed genital warts, but three in the placebo group did. And no one who received the vaccine developed pre-cancerous cervical lesions, but three who got the placebo did. Pain at the injection site was the only vaccine side effect.

Christopher Crum, director of women’s and perinatology pathology at the Brigham and Women’s Hospital in Boston, says he is “cautiously optimistic” that the experimental vaccine’s protective effect will last at least through a woman’s reproductive years. Crum isn’t involved with the Merck vaccine trials.

Barr and Villa’s paper suggests that universal HPV vaccination might be most effective in 10-to-13-year-olds, who are not likely to be infected with HPV. The large ongoing trial includes boys and girls as young as 9, Barr says.