Or poor fucking diets, sedentary lifestyle and global warming (had to slide that in, someone else would have) ....
Reference...
The hypothesis that the timing of vaccines either causes or prevents diabetes was tested in 21,421 children who received the Haemophilus influenzae type b (Hib) conjugate vaccine between 1988 and 1990 in the United States. These children were followed for 10 years after receiving the Hib vaccine. The risk of diabetes was indistinguishable from a group of 22,557 children who did not receive the Hib vaccine.
Correlation does not equal causeation.