CoV--a decisive • VitD deficiency-risk factor pathology Vitamin D SARS-CoV-2-Virus suppl.Hans-Klaus Goischke ( 2024) SARS-CoV-2 Infection and Multiple Sclerosis: Proactive Approach in a Vulnerable Patient Group through Daily Vitamin D Supplementation? rate was significantly lower than with values below or with deficiency [17]. Current data suggest a protective role for VitD, particularly with a lower risk of intensive care unit admission and a reduced risk of death [18,19]. In addition, the occurrence of Long-Covid is an aspect of implementing this simple, effective, safe and costeffective therapy with a broad therapeutic window for the prevention and treatment of COVID-19 disease [20-22]. Although there is still no indisputable evidence that Vit D supplementation (VitD suppl.) reduces the risk of SARSCov-2 infection in healthy individuals, there is collective evidence that it benefits vulnerable individuals [23]. PwMS with comorbidities, psychiatric illnesses, hypertension, obesity (an increased BMI may correlate with a severe course of Covid-19), age > 50 years, severe disability and methylprednisolone boost therapy as well as some DMTs (disease-modifying therapies) have a higher risk of infection and an increased risk of severe COVID-19 courses [24-26]. Infections (SARS-COV-2) can increase MS symptoms (pseudo-relapses) or cause real relapses [27]. In post-COVID syndrome (Long Covid), one in eight patients presents with symptoms such as fatigue, shortness of breath, cough, joint pain, chest pain, muscle pain, headache and paresthesia in the limbs after at least 3 months. The latter can also occur in PwMS per se [28,29]. If vitamin D administration results in a lower risk of infection, severity of illness with admission to the intensive care unit or a reduced risk of death in people at risk, Long-Covid occurs less frequently [18,19,21,22,[30][31][32][33], it is not ethically justifiable to withhold high dose vitamin-D administration from people at risk.