Diabet. Med. 28, 1530–1536 (2011) Aims  To evaluate the long‐lasting immunogenicity and safety of a pandemic vaccine co‐administered with a seasonal influenza vaccine in young subjects with Type 1 diabetes. Methods  Eighty patients (mean age: 16.7 ± 5.5 years, disease duration: 10.2 ± 4.7 years) were randomly assigned to receive a single or a double dose (1 month apart) of MF59‐adjuvanted influenza A(H1N1) vaccine, simultaneously with a single dose of a virosome‐adjuvanted trivalent influenza vaccine for the 2009–2010 season. Results  One month after immunization, the rate of seroconversion to 2009 pandemic A(H1N1) was 92.5% with an overall 100% proportion of vaccinees with protective antibody titres (≥ 1:40). No significant differences were observed between vaccinees who received the one‐dose or the two‐dose schedule. Seasonal vaccine induced a significant increase of both seroprotection rates and antibody levels. Local adverse events at the injection site of pandemic and seasonal vaccines were reported by 66.3% and 50% of subjects, respectively. Solicited systemic adverse events, mainly mild in intensity, were reported by 26.7% of vaccinees. No subjects had an influenza‐like illness during the 6‐month follow‐up. Conclusions  One injection of 2009 pandemic influenza A(H1N1) MF59‐adjuvanted vaccine is immunogenic and safe in young patients with Type 1 diabetes who are at increased risk of influenza morbidities. Pandemic vaccine can be safely co‐administered with seasonal influenza vaccine.