A vaccine including recombinant vaccinia virus (ATCC VR-1354) having an inserted
gene for coding glutamic acid decarboxylase is used for preventing type 1 diabetes
mellitus. The glutamic acid decarboxylase expressed from the recombinant virus
suppresses or tolerizes the autoreactive T cell, and induces immunological tolerance,
thus effectively prevents or delays the development of type 1 diabetes mellitus.