AACR: Cervical Cancer Vaccines Show Long-Term Safety and Efficacy

April 18, 2007

LOS ANGELES -- Cervarix, an investigational cervical cancer vaccine, prevented all precancerous lesions because of human papillomavirus types 16 and 18 for 5.5 years, researchers reported here.

LOS ANGELES, April 18 -- Cervarix, an investigational cervical cancer vaccine, prevented all precancerous lesions because of human papillomavirus types 16 and 18 for 5.5 years, researchers reported here.

Also, researchers studying Gardasil, the FDA-approved HPV vaccine, said that the vaccine had been safe and effective in more than 5,300 women followed for an average of three years.

Both studies were presented at the American Association for Cancer Research meeting.

The long-term data from the Cervarix also found durable and "significant cross protection for HPV types 45 and 31," said Stanley Gall, M.D., of the University of Louisville.

Evidence of cross protection is important, Dr. Gall said, because while HPV types 16 and 18 cause about 70% of cervical cancers, other HPV types are responsible for the remaining 30%.

Current estimates are that 50.3% of cervical cancers are associated with HPV 16, 22% with HPV 18, 6.7% with HPV 45, 2.9% with HPV 31, and about 2% with HPV 52. These account for roughly 84% of cervical cancers. The remaining 16% is associated with more than a dozen additional HPV strains.

After 5.5 years, the antibody response against types 11 and 18 was at least 11 times greater than antibody levels associated with natural immune response to HPV infection, Dr. Gall said.

Dr. Gall said the immune response with Cervarix "appeared to peak at about 24 to 30 months, and it appears to hold steady at that point."

The Cervarix trial enrolled 1,113 women ages 15 to 25 in North America and Brazil. Women were randomized to the vaccine or placebo in three doses at 0, 1, and 6 months, he said. The extended follow-up phase tracked 776 of the original cohort who were followed with HPV 16 and 18 antibody testing and cervical samples at six-month intervals. Cytology was performed annually and referral for colposcopy and biopsy was per protocol, Dr. Gall said.

After 5.5 years there were no cases of HPV 16 or 18 associated cervical intraepithelial neoplasia (CIN) among women who received the Cervarix vaccine versus 11 CIN1+ and seven CIN2+ cases in the placebo group.