Effect of a Mycobacterium vaccae derivative on paediatric atopic dermatitis: a randomized, controlled trial.

Summary Background.  The prevalence of atopic diseases in the Western world is rising while infectious diseases decline. The ‘hygiene hypothesis’ suggests that reduced exposure to microbes such as mycobacteria in early life is associated with increased atopic disease. Recent research showed that Mycobacterium vaccae reduced the severity of atopic dermatitis (AD) in children. Objective.  To evaluate the efficacy of a derivative of heat-killed M. vaccae in children with AD. Methods.  In total, 129 children, aged 5–16 years old with moderate to severe AD participated in this randomized, double-blind, placebo-controlled trial. Participants received an intradermal injection of either M. vaccae or placebo three times at 2-weekly intervals. The two groups were compared for changes in severity and extent of AD from baseline to 3 and 6 months after treatment. Results.  There was no significant difference between the two groups for change in severity of AD at 3 and 6 months (P = 0.77 and P = 0.70, respectively) or in extent of disease at 3 months (P = 1.0). Local injection-site reactions occurred in 47% of participants, of whom 75% received M. vaccae. Conclusion.  In this study, M. vaccae did not improve AD significantly in children with moderate to severe disease.