Antibodies to Influenza Virus A / H 1 N 1 Hemagglutinin in Type 1 Diabetes Children Diagnosed Before, During and After the SWEDISH A ( H 1 N 1)pdm09 Vaccination Campaign 2009–2010

We determined A / H 1 N 1‐hemagglutinin (HA) antibodies in relation to HLA ‐ DQ genotypes and islet autoantibodies at clinical diagnosis in 1141 incident 0.7‐to 18‐year‐old type 1 diabetes patients diagnosed April 2009–December 2010. Antibodies to 35 S‐methionine‐labelled A / H 1 N 1 hemagglutinin were determined in a radiobinding assay in patients diagnosed before ( n = 325), during ( n = 355) and after ( n = 461) the October 2009–March 2010 Swedish A ( H 1 N 1)pdm09 vaccination campaign, along with HLA ‐ DQ genotypes and autoantibodies against GAD , insulin, IA ‐2 and ZnT8 transporter. Before vaccination, 0.6% patients had A / H 1 N 1‐ HA antibodies compared with 40% during and 27% after vaccination ( P < 0.0001). In children