Here, we study the impact of immunoglobulin A (IgA) coating of gut bacteria in infancy on allergic outcomes in two distinct populations: (1) an urbanized cohort of Rochester infants (ROC) enriched for allergies (prevalence of 40%) and (2) infants from a traditional, agrarian Old Order Mennonite (OOM) community with a low prevalence of allergies (less than 2%).<h4>Methods</h4>We performed immunoglobulin A sequencing (IgA-SEQ) on stool samples collected at an average of 6 months of life to assess gut microbiome IgA coating levels in 9 OOM and 21 ROC infants. Here, CD79A is linked to Allergy.