In patients with MS, DMT such as interferon (IFN)-β, glatiramer acetate and dimethyl fumarate (DMF) are not expected to compromise vaccine efficacy13, although the effect of DMF-induced lymphopenia on vaccine efficacy is unknown, and attenuated vaccine responses in patients with moderate or severe lymphopenia is conceivable14. Here, IFNB1 is linked to lymphopenia.