Recurrent venous thromboembolism occurred in 3 patients in the warfarin group and 25 patients in the placebo group ( HR , 0.15 ; 95 % CI , 0.05-0 .43 ) ; major bleeding occurred in 4 patients in the warfarin group and in 1 patient in the placebo group ( HR , 3.96 ; 95 % CI , 0.44 to 35.89 ) .