IFNB1 and relapsing-remitting multiple sclerosis: The number of observations supporting a protective effect of vitamin D in MS fostered the idea that vitamin D deficiency might be an important modifiable risk factor, and several clinical trials have been performed to evaluate the efficacy of vitamin D in relapsing-remitting MS (RRMS), also in combination with interferon β (IFNβ) [5,6,7].