Since type 1 diabetes is an immunologically mediated disease, immune 
intervention should alter the natural history of the disease. This article 
reviews prevention studies undertaken either prior to any evidence of 
autoimmunity (primary prevention) or after the development of islet 
autoantibodies (secondary prevention). Most immune intervention studies have 
been conducted in recent-onset type 1 diabetes (tertiary prevention), and these 
are not reviewed herein. The goal of primary and secondary intervention is to 
arrest the immune process and thus prevent or delay clinical disease. Primary 
prevention studies have been conducted in infants with high genetic risk. 
Interventions tested include several dietary manipulations, including infant 
formulas free of either cow's milk or of bovine insulin, infant formula 
supplemented with the omega-3-fatty acid docosahexaenoic acid, delayed 
introduction of gluten-containing foods, and vitamin D supplementation. 
Secondary prevention studies have been conducted in both children and adults 
with diabetes autoantibodies. Interventions tested include nicotinamide, insulin 
injections, oral insulin, nasal insulin, glutamic acid decarboxylase, and 
cyclosporine. Underway are secondary prevention studies with teplizumab and with 
abatacept.