BCG vaccine for clinically isolated syndrome and MS

Infections may be harmful for people with multiple sclerosis (MS), resulting in fever, "pseudo-exacerbations," and increased risk of relapses.1 Can infections ever be beneficial for MS? The long-held yet unproven "hygiene hypothesis" proposes that certain infections early in life might reduce the risk of developing autoimmune diseases by inducing protective immunity.2 In addition, parasitic intestinal infections in people with MS may reduce disease activity.3 It follows that better sanitation and common use of disinfectants and antibiotics may account in part for the increased prevalence of MS and other autoimmune diseases in North America and much of Europe, compared with Africa, South America, and parts of Asia. If true, might we harness this natural phenomenon to develop new treatments for MS?