Long-lasting immunogenicity and safety of a 2009 pandemic influenza A(H1N1) MF59-adjuvanted vaccine when co-administered with a 2009-2010 seasonal influenza vaccine in young patients with type 1 diabetes mellitus.

Objective: 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.