Impact of CORona Virus Pandemic on Allergic and Autoimmune Dysregulation in Infants Born During Lockdown. CORAL

Several hypotheses link reduced microbial exposure to increased prevalence of allergies, but none has been experimentally tested in humans. Here we capitalize on the opportunity to study a cohort of infants (CORAL), raised during COVID-19 associated social distancing measures, to test the hypothesis that reduced exposure to microbial biodiversity during the first year of life may increase risk of allergic outcomes. We show that the relative abundance of maternally acquired Bifidobacteria was higher while environmentally transmitted bacteria such as Clostridia were significantly less abundant in fecal samples of CORAL infants compared to previous cohorts. Plant based foods during weaning positively impacted microbiota development. The prevalence of allergen sensitization and atopic dermatitis at 12 and 24 months did not increase over expected levels. Our results suggest that vertically transmitted bacteria and appropriate dietary supports may be more important than exposure to environmental microbes alone for protection against allergic diseases in infancy.