BCG (Tuberculosis) Vaccine
Data has been published that immunization with the tuberculosis, also called BCG, vaccine starting at birth is associated with a decreased risk of IDDM. The data includes an ecological study of European countries (BCG Graph 1) (Classen,DC & Classen, 1997) as well as a cohort study from Sweden (BCG Graph 2) (Classen,JB & Classen, 1996; Classen,DC & Classen, 1997). In both studies the administration of one dose of BCG vaccine at birth is associated with a decreased risk of about 50 cases of IDDM/100,000 children immunized. Ecological data has also been published that immunization with BCG starting at school age is associated with an substantial increased risk of IDDM, possibly doubling one's risk of IDDM (BCG Graph 3). Interestingly the ecological data shows immunization at school age is not associated with an increased incidence of IDDM if a dose is also given at birth. Those countries where BCG vaccine is given at birth typically give booster shots at school age yet still have lower incidence than those countries not giving the BCG vaccine.
The Israeli government routinely immunized newborns with BCG until the practice was stopped in 1982 (Zilber, Simchen, Wartskiet al.1984). Since the discontinuation of the BCG vaccine at birth there has been a gradual increase in the incidence of IDDM in the younger populations in Israel (Shamis, Gordon, Albaget al.1997). This is also consistent with the previously described data.