HPV vaccine shows long-term efficacy

NEW YORK (Reuters Health) - The human papillomavirus (HPV)-16/18 AS04-adjuvanted vaccine (Cervarix) offers considerable protection against infection with HPV 16/18 up to 6.4 years after administration, according to a report in the December 3rd online issue of The Lancet.

"Prophylactic vaccines against HPV infection are expected to provide a major advance in the prevention of cervical cancer," Dr. Barbara Romanowski and The GlaxoSmithKline Vaccine HPV-007 Study Group write. "Such vaccines have to provide long-term protection, since the risk of acquiring an infection starts at sexual debut, and women remain vulnerable to development of HPV-related lesions throughout their life."

The findings stem from a combined analysis of initial (2001 to 2003) and follow-up (2003 to 2007) studies on the HPV vaccine. The women were 15 to 25 years of age at vaccination, had normal cytology, were seronegative for HPV-16/18, and had no oncogenic HPV DNA.

In the according-to-protocol efficacy cohort, 465 women received the vaccine and 454 were given placebo. In the total vaccinated cohort, 560 women received the vaccine and 553 were given placebo.

The vaccine was 95.3% effective against incident infection with HPV 16/18 and 100% effective against 12-month persistent infection. Vaccine efficacy against cervical intraepithelial neoplasia grade 2 and above for HPV-16/18-associated lesions and for HPV-independent lesions were 100% and 71.9%, respectively.

ELISA testing showed that antibody levels against both antigens were at least 12 times higher after vaccination than after natural infection.

No significant differences in serious adverse events were noted between the vaccine and placebo groups, with rates of 8% and 10%, respectively, during the follow-up study.

In a related editorial, Dr. Gary M. Clifford, from the International Agency for Research on Cancer, Lyon, France, comments that while the present findings "suggest that this window of protection (against infection with HPV-16/18) is at least 6 years," the immunogenicity data suggest that "the period of protection might be much longer."

Funding for the study was provided by GlaxoSmithKline, which manufactures and markets the vaccine as Cervarix.

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