Summary data from the Costa Rica Vaccine Trial ( CVT ; NCT00128661 ) and ~ the PATRICIA trial ( NCT001226810 ) , two phase 3 , double-blind , randomised controlled clinical trials of the HPV-16 / 18 AS04-adjuvanted vaccine in young women , were combined in a post-hoc analysis ( GlaxoSmithKline [ GSK ] e-track number 202142 ) to investigate the efficacy of fewer than three doses of the HPV-16 / 18 vaccine after 4 years of follow-up .