An experimental vaccine against one strain of the human papilloma virus blocked most infections by the virus and, more important, prevented development of a precursor of cervical cancer caused by the virus, researchers said Monday.
The results are an important step toward the eradication of cervical cancer, which strikes about 15,000 U.S. women annually, killing one-third of that number. Globally, the disease strikes half a million women every year and kills 60 percent of that number.
Researchers from the University of Washington presented data two years ago showing that the vaccine blocked new infections by the virus. The new data from the same group, presented in Washington at an infectious-diseases conference, shows that the protection persists for at least four years and demonstrates for the first time that it blocks cancer development.
The human papilloma virus is the major cause of cervical cancer. It also causes a variety of cervical problems that appear as abnormalities on a Pap smear, necessitating further tests to rule out the presence of cancer.
The vaccine is directed against just one of the 20 common papilloma viruses – HPV-16 – but that one strain infects 20 percent of the U.S. population and causes half of all cases of cervical cancer.
Merck & Co., the manufacturer of the current vaccine, is testing a second-generation version that would protect against four papilloma viruses that collectively cause 80 percent of cervical cancers and 90 percent of genital warts. The company will submit a new drug application for it to the Food and Drug Administration next year, said Dr. Eliav Barr of Merck, who is in charge of its development.
“We’re going to take a big chunk out of HPV-related disease,” he said.
Epidemiologist Laura Koutsky and her colleagues at the University of Washington gave the current single-virus vaccine in three doses to 755 women between ages 16 and 23. Another 750 received a placebo.
After an average of about 48 months, seven of the women who received the vaccine developed HPV-16 infections, compared with 111 infections among those who received the placebo.
More important, she said, none of those who received the vaccine showed signs of cervical intraepithelial neoplasias – localized lesions that, if not detected and removed, progress to cervical cancer.
“All of them were prevented, which is very exciting to see,” Koutsky said.
Of the women who received a placebo, 24 had lesions.
The vaccine is made of viruslike particles, grown in yeast, that have all of the surface proteins of the virus but none of its genetic information.
It was invented by Dr. Douglas Lowy of the National Cancer Institute. The government gave the rights to the vaccine to Merck and to GlaxoSmithKline Biologicals, but Merck is said to be slightly ahead in the race to bring it to market.