Background: Influenza A (H1N1) has emerged as a considerable threat for recipients of organ transplants. Vaccination against the novel influenza A (H1N1) virus has generally been advocated. There is limited experience with AS03-adjuvanted A/H1N1 pandemic influenza vaccines in immunosuppressed patients.
Methods: We conducted an observational, nonrandomized single-center study to assess antibody response and vaccine-related adverse effects in 47 heart transplant recipients (44 men; age, 56±13 years). The AS03-adjuvanted, inactivated split-virion A/California/7/2009 H1N1v pandemic vaccine was administered. Antibody titers were measured using hemagglutination inhibition; immunoglobulin G (IgG) response was assessed using a new pandemic influenza A IgG enzyme-linked immunosorbent assay (ELISA) test kit and compared with hemagglutination-inhibition titers. Adverse effects of vaccination were assessed by a questionnaire.
Results: Postvaccination antibody titers of greater than or equal to 1:40 were found in only 15 patients, corresponding to a seroprotection rate of 32% (95% confidence interval, 19%-47%). Sensitivity, specificity, positive predictive value, and negative predictive value of ELISA testing were 80.0%, 68.8%, 54.5%, and 88.0%, respectively. Age, time posttransplantation, and immunosuppressive regimen did not impact antibody response. Vaccination was well tolerated.
Conclusions: Single-dose administration of an AS03-adjuvanted vaccine against the novel influenza A (H1N1) virus did not elicit seroprotective antibody concentrations in a substantial proportion of heart transplant recipients; the new pandemic influenza A IgG ELISA test kit proved to be of limited clinical use.