Vaccination of patients with mild and severe asthma with a 2009 pandemic H1N1 influenza virus vaccine

Background: Asthma was the most common comorbidity of patients hospitalized with 2009 H1N1 influenza. Objective: We sought to assess the immunogenicity and safety of an unadjuvanted, inactivated 2009 H1N1 vaccine in patients with severe versus mild-to-moderate asthma. Methods: We conducted an open-label study involving 390 participants (age, 12-79 years) enrolled in October-November 2009. Severe asthma was defined as need for 880 mu g/d or more of inhaled fluticasone equivalent, systemic corticosteroids, or both. Within each severity group, participants were randomized to receive intramuscularly 15 or 30 mu g of 2009 H1N1 vaccine twice 21 days apart. Immunogenicity end points were seroprotection (hemagglutination inhibition assay titer >= 40) and seroconversion (4-fold or greater titer increase). Safety was assessed through local and systemic reactogenicity, asthma exacerbations, and pulmonary function. Results: In patients with mild-to-moderate asthma (n =217), the 2009 H1N1 vaccine provided equal seroprotection 21 days after the first immunization at the 15-mu g (90.6%; 95% CI, 83.5% to 95.4%) and 30-mu g (95.3%; 95% CI, 89.4% to 98.5%) doses. In patients with severe asthma (n = 173), seroprotection 21 days after the first immunization was 77.9% (95% CI, 67.7% to 86.1%) and 94.1% (95% CI, 86.8% to 98.1%) at the 15- and 30-mg doses, respectively (P = .004). The second vaccination did not provide further increases in seroprotection. Participants with severe asthma who are older than 60 years showed the lowest seroprotection (44.4% at day 21) with the 15-mg dose but had adequate seroprotection with 30 mg. The 2 dose groups did not differ in seroconversion rates. There were no safety concerns. Conclusion: Monovalent inactivated 2009 H1N1 pandemic influenza vaccine was safe and provided overall seroprotection as a surrogate of efficacy. In patients older than 60 years with severe asthma, a 30-mg dose might be more appropriate. (J Allergy Clin Immunol 2011;127:130-7.)