From the CDC website: "In 1998 a researcher presented a theory suggesting that vaccines, depending on when they are administered, may increase or decrease the risk that certain people may develop type 1 diabetes, previously called juvenile onset or insulin-dependent diabetes mellitus (IDDM). The cause of type 1 diabetes is not completely understood but it is believed that genetic and environmental factors may be involved. Vaccinations have been studied as a possible environmental risk factor and the scientific studies conducted have found no relationship between immunizations and type 1 diabetes."