Primary Objective:

To assess the distribution of IARs by severity grade when LEMTRADA is administered to RRMS patients who will be medicated according to specified algorithm designed to manage infusion associated reactions.

The total duration of participation in the study per patient is approximately 13.5 months.

After the end of the second course of LEMTRADA treatment, patients will be followed by their physician in a regular healthcare setting until 48 months safety monitoring period is completed.

Inclusion criteria:

• Adult RRMS patients who will be initiating treatment with Lemtrada according to local approved label.
• Signed written informed consent.

Exclusion criteria:

• Previously treated with LEMTRADA.
• Contraindications to LEMTRADA according to the labeling in the country.
• Any known contraindications to the symptomatic therapy used in the infusion management guidance based on their local approved label.
• Currently participating in another investigational interventional study.
• Any technical/administrative reason that makes it impossible to enroll the patient in the study.
• Patient is the Investigator or any Sub-investigator, research assistant, pharmacist, study coordinator, other staff or relative thereof directly involved in the conduct of the protocol.
• Patient who has withdrawn consent before enrollment (starting from signed informed consent form).
• Despite screening of the patient, enrolment is stopped at the study level.
• Woman of childbearing potential not protected by highly-effective method(s) of birth control (as defined in a local protocol amendment in case of specific local requirement) and/or who are unwilling or unable to be tested for pregnancy.
• Pregnancy (defined as positive beta human chorionic gonadotropin (β-HCG) blood test), breast feeding.
• Known infection with latent tuberculosis or active tuberculosis.
• Known infection with Hepatitis B, Hepatitis C.

The above information is not intended to contain all considerations relevant to a patient's potential participation in a clinical trial.