Placebo-controlled clinical trial with 900 COVID-19 patients shows success of a new patent-protected compound from the Cluster of Excellence PMI in Kiel (Germany). / An innovative nutritional supplementation restores physical performance significantly faster in patients with COVID-19. / For the first time, a targeted release of the vitamin B3 form nicotinamide from CICR-NAM tablets has been shown to influence the gut microbiome in COVID-19: a new way to combat COVID-19 and to reduce the consequences of the disease. / A secondary analysis shows that patients at risk who responded well to the intervention with vitamin B3 also develop fewer post-COVID symptoms.