The Cervarix vaccine against human papillomavirus (HPV) offers long-term protection of at least 6.4 years after administration, a new study has confirmed. Cervarix is made by UK-based GlaxoSmithKline, which funded the study.

"Prophylactic vaccines against HPV infection are expected to provide a major advance in the prevention of cervical cancer," wrote lead author Dr. Barbara Romanowski, University of Alberta, and GlaxoSmithKline Vaccine HPV-007 Study Group colleagues. "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 double-blind, randomized, placebo-controlled study involved 1,113 women ages 15-25 at 27 sites in three countries.

In the study group's according-to-protocol analysis (465 vaccine vs. 454 placebo), Cervarix was 95.3 percent effective against incident infection by the HPV types it targets, HPV 16 and 18, for 6.4 years. Efficacy against 12-month persistent infection was 100 percent. For the total vaccinated cohort (560 vaccine vs. 553 placebo), vaccine efficacy against cervical intraepithelial neoplasia grade 2 and above was 100 percent for HPV 16/18-associated lesions and 71.9 percent for lesions independent of HPV DNA.

Antibody concentrations measured by ELISA testing were 12-fold or more compared with natural HPV infection for both antigens. Safety outcomes were similar between groups, with serious adverse events reported by 8 percent of participants in the vaccine group and 10 percent in the placebo group. None was judged related or possibly related to the vaccine, and no deaths occurred.

The findings "suggest that this window of protection (against infection with HPV-16/18) is at least six years," and immunogenicity data suggest "the period of protection might be much longer," Dr. Gary M. Clifford of the International Agency for Research on Cancer wrote in an accompanying editorial.

The study, "Sustained Efficacy and Immunogenicity of the Human Papillomavirus (HPV)-16/18 AS04-Adjuvanted Vaccine: Analysis of a Randomised Placebo-Controlled Trial up to 6.4 Years," and the editorial, "Global Access to HPV Vaccination: What Are We Waiting For?" were published in The Lancet (2009;374(9706):1975-1985 and 1948-1949).