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Background: Natalizumab (NAT) has a strong impact on disease activity of aggressive pediatric multiple sclerosis (MS), with no difference in safety profile compared to adult MS. However, available data are limited by short follow-up. Our aim was to report long-term follow-up data (up to 11 years) of a large Italian pediatric MS cohort treated with NAT. Materials and methods: We retrospectively collected data of pediatric MS patients treated with NAT included in a previous study and prospectively followed in Italian MS centers. We compared disease activity pre, during, and post-NAT and we performed survival analyses of time to evidence of disease activity (EDA) during NAT, time to reach EDA post-NAT, and time to NAT discontinuation. Results: Ninety-two patients were included from 19 MS centers in Italy. At NAT initiation, cohort's characteristics were as follows: 55 females; 14.7 ± 2.4 (mean ± SD) years of age; 34 naïve to disease modifying therapies; 1-year pre-NAT annualized relapse rate (ARR): 2.2 ± 1.2; EDSS (median [IQR]): 2.5 [2.0–3.0]; gadolinium-enhancing lesions: 2 [1–5]; 41 JCV positives. During NAT treatment (61.9 ± 35.2 mean infusions), ARR lowered to 0.08 ± 0.23 (p < 0.001), EDSS score to 1.5 [1.0–2.5] at last infusion (p < 0.001), and 51% patients had EDA (21% after 6 months of rebaseline). No serious adverse events were reported. Forty-nine patients discontinued NAT, mainly due to PML concern; the majority (29/49) had disease reactivation in the subsequent 12 months, of which three with a clinical rebound. Conclusion: NAT treatment maintains its high efficacy for a long time in pediatric MS patients, with no new safety issues. [ABSTRACT FROM AUTHOR]