Relapse was defined as new neurological symptoms or worsening of previous neurological symptoms with an objective change on neurological examination, attributable to multiple sclerosis (MS) that last for at least 48 hours, present at normal body temperature, and that were preceded by at least 30 days of clinical stability. ARR was obtained from the total number of confirmed relapses that occurred during the treatment follow-up time of all participants divided by the sum of follow-up time of all participants involved in certain treatment groups. ARR was estimated through negative binomial regression with robust variance estimation.

Relapse was defined as new neurological symptoms or worsening of previous neurological symptoms with an objective change on neurological examination, attributable to MS that last for at least 48 hours, present at normal body temperature, and that were preceded by at least 30 days of clinical stability. ARR was obtained from the total number of confirmed relapses that occurred during the treatment follow-up time of all participants divided by the sum of total follow-up time of all participants involved in certain treatment groups. ARR was estimated through repeated negative binomial regression with robust variance estimation and covariate adjustment for geographic region. The IFNB-1a/Alemtuzumab switch from CAMMS323 or CAMMS324 to CAMMS03409 pre alemtuzumab reporting group consisted of the same participants as those in the corresponding post alemtuzumab reporting group.

Relapse was defined as new neurological symptoms or worsening of previous neurological symptoms with an objective change on neurological examination, attributable to MS that last for at least 48 hours, present at normal body temperature, and that were preceded by at least 30 days of clinical stability. ARR was obtained from the total number of confirmed relapses that occurred during the treatment follow-up time of all participants divided by the sum of total follow-up time of all participants involved in certain treatment groups. ARR was estimated through negative binomial regression with robust variance estimation without covariate adjustment.

SAD: defined as an increase of at least 1.5 points in Expanded Disability Status Scale (EDSS) score for participants with prior study baseline score of 0 and increase of at least 1.0 point for participants with a prior study baseline score of 1.0 or more; and the increase persisted over a 6-month consecutive period. EDSS is an ordinal scale in half-point increments that quantifies disability in participants with MS. It assesses 7 functional systems (visual, brainstem, pyramidal, cerebellar, sensory, bowel/bladder and cerebral) and ambulation. EDSS total score ranges from 0 (normal neurological examination) to 10 (death due to MS), higher scores indicating worse neurological function. Number of participants with SAD was estimated by Kaplan-Meier method and reported in this outcome measure. Baseline was defined as Year 0 of CAMMS323 and Year 0 of CAMMS324 for "alemtuzumab treatment CAMMS323 extension" group and "alemtuzumab Treatment CAMMS324 Extension" group, respectively.

SAD: defined as an increase of at least 1.5 points in EDSS score for participants with prior study baseline score of 0 and increase of at least 1.0 point for participants with a prior study baseline score of 1.0 or more; and the increase persisted over a 6-month consecutive period. EDSS is an ordinal scale in half-point increments that quantifies disability in participants with MS. It assesses 7 functional systems (visual, brainstem, pyramidal, cerebellar, sensory, bowel/bladder and cerebral) and ambulation. EDSS total score ranges from 0 (normal neurological examination) to 10 (death due to MS), higher scores indicating worse neurological function. Number of participants with SAD over 2 years before and 2 years after alemtuzumab treatment were estimated by Kaplan-Meier method and reported in this outcome measure. The IFNB-1a/Alemtuzumab switch pre alemtuzumab reporting group consisted of the same participants as those in the corresponding post alemtuzumab reporting group.

EDSS is an ordinal scale in half-point increments that qualifies disability in participants with MS. It assesses 7 functional systems (visual, brainstem, pyramidal, cerebellar, sensory, bowel/bladder and cerebral) as well as ambulation. EDSS total score: 0 (normal neurological examination) to 10 (death due to MS). As measured by EDSS score, SAD was defined as increase of at least 1.5 points for participants with Baseline score of 0 and increase of at least 1.0 point for participants with a Baseline score of 1.0 or more; and the increase persisted for at least the next 2 scheduled assessments, that is, 6 consecutive months. The onset date of SAD was date of first EDSS assessment that began 6 month consecutive period of SAD. Participants who did not reach SAD endpoint were censored at their last visit. Percentage of participants with SAD, estimated by Kaplan-Meier (KM) method, was reported.

Relapse was defined as new neurological symptoms or worsening of previous neurological symptoms with an objective change on neurological examination, attributable to multiple sclerosis that lasted for at least 48 hours, that were present at normal body temperature, and that were preceded by at least 30 days of clinical stability. Annualized relapse rate was estimated through negative binomial regression with robust variance estimation and covariate adjustment for geographic region using observed number of relapses as dependent variable, the log total amount of follow-up from date of first study treatment for each participant as an offset variable, and treatment group and geographic region as model covariates.