The expression of the OAS1 isoform p46 encoded by the presence of the G allele leads to: (1) High OAS enzyme activity in leukocytes from Type 1 diabetics, (2) Low response to measles vaccination and higher virus-specific IL-2 secretion during rubella vaccination, and (3) Inhibition of WNV, HCV and Dengue virus replication. This evidence concerns the gene IL2 and measles.