The annual publication of subpar U.S. vaccination rates against human papillomavirus (HPV) consistently shows that while half of teenage girls receive one dose, far fewer come back to complete the regimen. What is less clear is whether one dose offers any protection, but a new study offers some hope.
A randomized trial of GlaxoSmithKline's ($GSK) bivalent HPV vaccine Cervarix in Costa Rica found that women who received one dose of the vaccine had an immune response, although antibody levels were higher in those who received two or three jabs. The antibody levels in women who received one dose were stable four years later. While it is unclear what antibody level is needed to confer protection--and the study looked at Cervarix, not Merck's ($MRK) more widely used Gardasil--the trial still suggests one dose might do some good.
The result is a positive for the American teenage girls who only receive one dose, and also has implications for the developing world, where the cost and inconvenience of the three-dose regimen limits uptake. "Cervix cancer is generally one of the leading causes of cancer death in women in the third world. These areas don't have big healthcare budgets and if we can give one dose of HPV vaccine that can provide a measure of protection, as this study suggests, that's really exciting news," Cleveland Clinic gynecologic oncologist Dr. Robert DeBernardo, who was not involved with the research, told Reuters Health.
An earlier study by the same team found that one or two doses of Cervarix provided similar protection as three doses against persistent HPV16/18 infection over 4 years. The finding prompted the team to look into the underlying antibody responses and ultimately to the data published in Cancer Prevention Research this week. Real-world evidence of the effectiveness of a two-dose regimen could soon arrive to back up the trial data. Switzerland and parts of Canada have already adopted a two-dose schedule, and positive data from these regions could prompt other healthcare systems to switch, potentially dampening vaccine sales.
Special Report: The 20 top-selling vaccines in H1 2012