Clustering of cases of insulin dependent diabetes (IDDM) occurring three years after hemophilus influenza B (HiB) immunization support causal relationship between immunization and IDDM.
OBJECTIVE
The hemophilus vaccine has been linked to the development of autoimmune type 1 diabetes, insulin dependent diabetes (IDDM) in ecological studies.


METHODS
We attempted to determine if the Hemophilus influenza B (HiB) vaccine was associated with an increased risk of IDDM by looking for clusters of cases of IDDM using data from a large clinical trial. All children born in Finland between October 1st, 1985 and August 31st, 1987, approximately 116,000 were randomized to receive 4 doses of the HiB vaccine (PPR-D, Connaught) starting at 3 months of life or one dose starting after 24 months of life. A control-cohort included all 128,500 children born in Finland in the 24 months prior to the HiB vaccine study. Non-obese diabetic prone (NOD) mice were immunized with a hemophilus vaccine to determine if immunization increased the risk of IDDM.


RESULTS
The difference in cumulative incidence between those receiving 4 doses and those receiving 0 doses is 54 cases of IDDM/100,000 (P = 0.026) at 7 years, (relative risk = 1.26). Most of the extra cases of IDDM appeared in statistically significant clusters that occurred in periods starting approximately 38 months after immunization and lasting approximately 6-8 months. Immunization with pediatric vaccines increased the risk of insulin diabetes in NOD mice.


CONCLUSION
Exposure to HiB immunization is associated with an increased risk of IDDM. NOD mice can be used as an animal model of vaccine induced diabetes.