Vaccine 29 (2011) 6888–6893 Contents lists available at ScienceDirect Vaccine j ourna l ho me pag e: www.elsevier.com/locate/vaccine Pandemic influenza A H1N1 vaccine in recipients of solid organ transplants: Immunogenicity and tolerability outcomes after vero cell derived, non-adjuvanted, whole-virion vaccination Heimo Lagler a , Judith M. Wenisch a , Selma Tobudic a , Guido A. Gualdoni a , Susanne Rödler b , Susanne Rasoul-Rockenschaub c , Peter Jaksch d , Monika Redlberger-Fritz e , Theresia Popow-Kraupp e , Heinz Burgmann a,∗ a Division of Infectious Diseases and Tropical Medicine, Department of Medicine 1, Medical University of Vienna, Waehringer Guertel 18-20, 1090 Vienna, Austria b Division of Heart Surgery, Department of Surgery, Medical University of Vienna, Austria c Division of Transplantation, Department of Surgery, Medical University of Vienna, Austria d Department of Cardiothoracic Surgery, Medical University of Vienna, Austria e Institute of Virology, Medical University of Vienna, Austria a r t i c l e i n f o Article history: Received 7 March 2011 Received in revised form 26 June 2011 Accepted 16 July 2011 Available online 29 July 2011 Keywords: Influenza A (H1N1) Vaccine Solid organ transplantation Immunogenicity Tolerability a b s t r a c t During the 2009/10 pandemic of influenza A (H1N1), the American Society of Transplantation and other health organizations recommended that immunocompromised patients should be vaccinated as the key preventive measure. Since there are no data available for the immunogenicity of the unadjuvanted pan- demic influenza vaccine in immunocompromised patients – as opposed to the adjuvanted preparation – the objective of this study was to evaluate the immunogenicity of an adjuvant-free H1N1 vaccine in recipients of solid organ transplants. Patients were recruited at the Vienna General Hospital, Austria. The vaccination schedule consisted of 2 doses of a whole-virion, vero cell derived, inactivated, non-adjuvanted influenza A/California/07/2009 (H1N1) vaccine given with an interval of 3 weeks. A hemagglutination inhibition (HI) assay on blood samples obtained prior to the first and after each vaccination was used for serologic analysis. The primary immunologic endpoint was the seroconversion rate, defined as the pro- portion of subjects with an individual 4-fold increase in HI titer of at least 1:40. In addition, virus-specific IgG antibodies to the pandemic H1N1 strain were measured using a commercially available ELISA. Twenty-five organ transplant patients (16 males, 9 females) aged 25–79 years were vaccinated and provided blood samples for serologic analysis. The time elapsed since transplantation was 10 months to 25 years (mean: 9 years; 95% CI 6–13 years). The vaccine was well tolerated and no local adverse events were noticed. After two vaccinations 37% of the patients demonstrated seroconversion in the HI assay as defined above and 70% had virus-specific IgG antibodies. Among the HI vaccine responders were 6 of 14 heart transplant recipients and 1 of 4 liver transplant recipients. The number and type of immunosuppressive agents did not significantly differ in their effect on the immune response. Our results show that the novel vero cell derived and adjuvant-free pandemic A/California/07/2009 (H1N1) influenza vaccine induced limited but measurable immune responses in adult recipients of solid organ transplants. © 2011 Elsevier Ltd. All rights reserved. 1. Introduction In influenza infection, recipients of solid organ transplants (SOTs) are at increased risk of higher morbidity, mortality [1] and a lower immune response to vaccination [2–4] compared with immunocompetent individuals. It is therefore not surprising that more severe courses of pandemic H1N1 influenza have occurred in ∗ Corresponding author. Tel.: +43 1 40400 4440; fax: +43 1 40400 4418. E-mail address: heinz.burgmann@meduniwien.ac.at (H. Burgmann). SOT patients. A recent multicenter study in 237 patients found more cases of severe illness in SOT recipients than in healthy individu- als: 32% of the infected transplant recipients developed pneumonia and 16% needed admission to intensive care units [5]. During the 2009/10 pandemic of influenza A (H1N1), the American Society of Transplantation [6] and other health authorities recommended that all SOT recipients and their close contacts should receive an inacti- vated influenza vaccine, although the efficacy of this intervention was uncertain at that time. Antibody titers as an indicator of immu- nity and a surrogate marker for clinical protection against influenza or severe outcome of influenza infection are currently the method 0264-410X/$ – see front matter © 2011 Elsevier Ltd. All rights reserved. doi:10.1016/j.vaccine.2011.07.050