BCG immunization was routinely given to elementary and junior high school students in Japan until it was
abruptly discontinued after 2002. Data on the incidence of type 2 diabetes was analyzed to see if there was a change following
discontinuation of BCG. The incidence of type 2 diabetes dropped by over 50% in children from Tokyo following
discontinuation of BCG immunization, the relative risk reached 2.78 (95% confidence interval 1.03 - 7.480). This drop
appears to be more significant given the epidemic of type 2 diabetes in children around the world. The increased secretion
of cortisol following immunization is thought to result in metabolic syndrome and type 2 diabetes. Japanese children produce
larger amounts of cortisol following immunization than White children. This increased production of cortisol may
explain why Japanese children have a high risk of type 2 diabetes but low risk of type 1 diabetes compared to White children.
The proposed mechanism may explain the epidemic of obesity which starts in children under 6 months of age.