Factors associated with humoral immune response to pandemic A/H1N1(v) 2009 influenza vaccine in cystic fibrosis.

Influenza vaccination is recommended in cystic fibrosis patients. The objective of this study was to assess the immunogenicity of vaccination against 2009 pandemic A/H1N1 influenza and to study the factors associated with the immune response in patients with cystic fibrosis. 122 patients with cystic fibrosis were enrolled in a prospective study and received 1 dose of 2009/H1N1v adjuvanted vaccine, or for children <2 years and lung-transplanted patients, two doses of non-adjuvanted 2009/H1N1v vaccine administered 21 days apart. Hemagglutination inhibition antibodies were assessed before and 21 days after vaccination and at least 6 months after vaccination. After vaccination, 85% of the patients had an influenza antibody titer ≥1:40 and 69% seroconverted. 13% of the transplanted patients seroconverted compared with 72% of the non-transplanted patients. In this latter group, non-adjuvanted vaccine and low body mass index were independently associated with lower response to vaccination. 86% of the non-transplanted patients with normal BMI and receiving adjuvanted vaccine seroconverted. Persistence of seroprotection 10 months after vaccination was found in 50% of the patients. In patients with cystic fibrosis, malnutrition and receipt of non-adjuvanted vaccine were associated with lower immune response to pandemic influenza vaccination. Our data also suggest a potential defect in the immune response to influenza vaccination of patients with cystic fibrosis and raise the question of whether a different immunization strategy is needed.