The lifetime risk for HPV infection is about 80 percent in men and women.

The vaccine against the most common cancer-causing strains of human papillomavirus was 100 percent effective at preventing the persistent infections that cause cervical cancer, according to the published article. 

Will Save Lives

"This study provides objective evidence that this vaccine will work, it's going to save lives and will have a major impact on women's health care," says Dr. Daron G. Ferris, a study co-author who directs the Gynecologic Cancer Prevention Center at the Medical College of Georgia in Augusta.

"This is a tremendous advancement for women in particular, although it's likely the vaccine will one day be given to men as well," Dr. Ferris says of the bivalent vaccine that protects against types 16 and 18, which also cause penile cancer.

MCG was the largest study site in North America, with 83 women age 15 to 25 in the study taking three doses of vaccine over six months, then being followed for up to 27 months.

When the vaccine was taken correctly, it was 91.6 percent effective at reducing incident or new infections, the study showed. Researchers noted the vaccine prompted the body to produce high numbers of antibodies to fight the HPV infection and the only side effects were some redness and irritation at the vaccine site.

Youngsters May Be Targeted

"The efficacy of the bivalent vaccine against HPV 18 infection is particularly important," Drs. Matti Lehtinen and Jorma Paavonen of the National Public Health Institute in Finland note in a companion editorial.

Pap smears, used to detect cervical cancer or precancerous changes of the cervix, are not as good at detecting adenocarcinoma, the type of cervical cancer most associated with HPV 18. "Adenocarcinoma is difficult to find even when we know it's there," Dr. Ferris says of tests and biopsies that typically follow an abnormal Pap smear.

Dr. Ferris notes that the vaccine won't prevent all cervical cancers because it doesn't protect against all cancer-producing strains. However, a quadrivalent vaccine that also protects against types 6 and 11 – the most common causes of genital warts – already is under study, and more of the some 100 strains of the virus likely will be added as various vaccines are further developed, he says.

Should the Food and Drug Administration approve these vaccines for general use, the target audience likely would be girls and boys age 10 to 12 who are not yet sexually active, Dr. Ferris says.

The 15-25-year-old age group featured in The Lancet study has the highest incidence of this ubiquitous virus; the lifetime risk for HPV infection is about 80 percent in men and women, he says. About 13,000 women are diagnosed with cervical cancer each year in the United States. Penile cancer is rare, accounting for less than 1 percent of all cancers in men; the risk is higher in uncircumcised men.