In patients with an increase in EDSS of 0.5 or 1.0 during relapse , natalizumab increased the probability of 12-week confirmed complete recovery from relapse by 55 % ( hazard ratio [ HR ] = 1.554 ; P = 0.0161 ) and 67 % ( HR = 1.673 ; P = 0.0319 ) compared to placebo , respectively .