Effect of switching on the relapse rate measured as incidence rate ratio (IRR), using a Poisson regression model, after adjusting for baseline EDSS, disease duration and time on first-line disease modifying therapy.

Within group comparison compares the relapse rate before and after the switch for each group. The between group comparison compares treatment effect on immunosuppressant and natalizumab groups with non-switchers or between natalizumab and immunosuppressants.