Diverse microbial exposure - Consequences for vaccine development

► The term “hygiene hypothesis” is unfortunate, as neither poor hygiene nor infections, but microbial diversity, is the issue. ► Gut microbiota, including probiotic bacteria, may become novel opportunities as adjuvants and/or delivery vehicles for vaccines. ► The role of gut microbiota on immune function are most pronounced in infancy. ► Current vaccines do not have any major effect on the risk for childhood allergies.