The antibody response to pandemic H1N1 2009 influenza vaccine in adult organ transplant patients

Limited data are available regarding antibody response and the safety of the monovalent influenza A H1N1/09 vaccine for immunocompromised patients. In this study, the humoral response to this vaccine in solid organ transplant (SOT) recipients and healthy individuals was evaluated. Eighty‐two SOT recipients and 28 healthy individuals received two doses of the influenza A H1N1/09 AS03 adjuvanted vaccine containing 3.75 mg of haemagglutinin at a 3‐ to 4‐week interval. Serum samples were drawn at baseline and 3–4 weeks after the first and second vaccine doses. Seroprotective titres were measured with a haemagglutination inhibition. After the first dose seroprotective titres were observed in 69% of the SOT patients and in 96% of the healthy controls (P = 0.006), and increased after the second dose to 80% and 100%, respectively (P = 0.003). All controls and 77% of the SOT recipients achieved a ≥4‐fold titre rise after the first immunisation (P = 0.005). The vaccine was well tolerated and no acute rejection was observed. Influenza A H1N1/09 vaccine elicited a protective antibody response in the majority of SOT recipients, but the response was lower when compared with controls. A second dose significantly improved vaccine immunogenicity in SOT recipients. (ClinicalTrials.gov number: NCT01254955)