Comparison of immunogenicity and safety of a virosome influenza vaccine with those of a subunit influenza vaccine in pediatric patients with cystic fibrosis

The objective of this study was to compare the immunogenicity and safety of a single dose regimen and a two-dose regimen of a trivalent virosome influ enza vaccine (Inflexal Berna V) with those of a trivalent subunit influenza vaccine (Influvac) in children and adolescents with cystic fibrosis (CF), In an open, randomized, multicenter study with parallel groups, 11 young ch ildren with CF (1 to 6 years old) and 53 older children and adolescents wit h CF (>6 years old) were randomly assigned to one of the following immuniza tion regimens: virosome vaccine at 0.5 ml on study day 0 or 0.25 ml on days 0 and 28 or a standard regimen of subunit vaccine, i.e., 0.5 ml on day 0 f or older children and 0.25 ml on days 0 and 28 for younger children. Safety assessments, i.e., recording of systemic and local adverse events (AEs) an d vital signs, were made for a 5-day observation period after each immuniza tion, Hemagglutination inhibition (HI) titers were determined at baseline a nd 4 weeks after the single-dose and the two-dose immunizations, respective ly. Immunogenicity was assessed according to the criteria of the European A gency for the Evaluation of Medicinal Products (EMEA). Both vaccines induce d comparable HI antibody titers. Seroconversion (greater than or equal to 4 -fold rise in HI antibody titers, reaching a titer of greater than or equal to 1:40) was achieved in 41 to 100% of the participants. Seroprotection (H I titer, greater than or equal to 1:40) and a >2.5-fold increase in geometr ic mean titers were achieved in 100% of the participants. Thus, all three E MEA requirements for influenza vaccine efficacy were met by all treatment g roups and for both vaccines. The virosome vaccine, when administered as a s ingle dose, seemed to induce superior immunogenicity compared with the stan dard pediatric two-dose regimen. Totals of 42 and 57% of vaccinees receivin g virosome and subunit vaccines, respectively, reported at least one local AE (predominantly pain). Totals of 84 and 71% of subjects receiving virosom e and subunit vaccines, respectively, complained in response to questions o f at least one systemic AE (mainly cough, fatigue, coryza, or headache). Th e majority of events were mild or moderate and lasted 1 or 2 days only. No obvious relationship was found between AE reporting rate and vaccine formul ation, age group, or dose regimen. The relatively high AE reporting rate se emed to be partly related to the symptomatology of the underlying CF diseas e. In summary, the virosome and subunit vaccines induced in both age groups and against all three influenza strains an efficient immune response and w ere well tolerated by the children and adolescents with CF.