Early life Bacillus Calmette-Guerin vaccination and incidence of type 1, type 2, and latent autoimmune diabetes in adulthood

Aims Bacillus Calmette-Guerin (BCG) vaccination limits blood sugar elevations and autoimmunity. Previous studies focused on type 1 diabetes among children, despite possible effects on other phenotypes later in life. We studied associations between BCG vaccination and type 1, type 2 and latent autoimmune diabetes (LADA) in adulthood. Methods A 1970–1974 birth cohort was linked with the BCG vaccination registry and administrative health data of Quebec. 396,118 people aged 22–44 years were followed-up for diabetes mellitus (DM) onset. Incident DM cases were subjects with ≥1 hospitalization or ≥2 physician claims related to DM over a 2-year period. Type 1 diabetes, type 2 diabetes, and LADA cases were individuals with ≥1 reimbursement of insulin, oral antidiabetic agent, or both. Cox proportional regressions were used to estimate hazard ratios (HR), adjusting for potential confounders. Results Forty-four percent of subjects were BCG vaccinated, 88% of these before age 1. For type 1 diabetes, no association was found before 30 years old, but vaccinated subjects had a lower risk of this phenotype after age 30 (HRadj= 0.65, 95% CI: 0.44–0.95). BCG vaccination was associated with a lower risk of type 2 diabetes (HRadj=0.85, 95% CI: 0.79–0.92), whereas no association was observed for LADA (HRadj=1.30, 95% CI: 0.71–2.38). Results did not differ by sex. Conclusions Early life BCG vaccination was associated with lower risks of both type 1 and type 2 diabetes from early to middle adulthood, but not of LADA. Future studies should explore these long-term associations, while distinguishing diabetes phenotypes.