Retrospective analyses in subgroups showed that a treatment effect on disability progression is most likely in patients with active disease before treatment commences (Hazard Ratio 0.72, 95% confidence interval (0.59, 0.88), p=0.0011, corresponding to a 28% risk reduction due to Betaferon in patients with relapses or pronounced EDSS progression, 8 million IU Betaferon versus all placebo patients).