One or two doses of the HPV vaccine Cervarix may be as effective in protecting against persistent HPV infections as the standard three-dose regimen, new research suggests.
US researchers looked at data from the Costa Rica Vaccine Trial in which 7,000 women were assigned to receive either Cervarix or a control.
Some 5,967 women had three doses of the vaccine, 802 had two doses and 394 had one dose and participants were followed up for four years.
The efficacy of the vaccine against newly detected HPV -16 or HPV-18 that persisted for at least one year was 80.9% for three doses, where there were 25 and 133 events in the vaccine and control arms respectively.
Efficacy was 84.1% for two doses, with three and 17 events respectively, and 100% for one dose, with one and 10 events respectively. The trend for increasing vaccine efficacy with fewer doses was not statistically significant.
Study leader Dr Aimée Kreimer, an investigator in the division of cancer epidemiology and genetics at the US National Cancer Institute, concluded: ‘We provide the first clinical evidence that two doses of the bivalent HPV vaccine are highly efficacious…and that even a single dose may be highly efficacious.”
J Natl Cancer Inst 2011, online 9 September