Low-dose intradermal versus intramuscular trivalent inactivated seasonal influenza vaccine in lung transplant recipients

Background In this study we compared the immunogenicity of influenza vaccine administered intradermally to the standard intramuscular vaccination in lung transplant recipients. Methods Patients were randomized to receive the trivalent inactivated seasonal 2008–9 influenza vaccine containing either 6 μg (intradermal) or 15 μg (intramuscular) of hemagglutinin per viral strain. Immunogenicity was assessed by measurement of geometric mean titer of antibodies using the hemagglutination-inhibition (HI) assay. Vaccine response was defined as a 4-fold or higher increase of antibody titers to at least one vaccine antigen. Results Eighty-five patients received either the intradermal ( n = 41) or intramuscular ( n = 44) vaccine. Vaccine response was seen in 6 of 41 patients (14.6%) in the intradermal vs 8 of 43 (18.6%) in the intramuscular group ( p = 0.77). Seroprotection (HI ≥1:32) was 39% for H1N1, 83% for H3N2 and 29% for B strain in the intradermal group vs 28% for H1N1, 98% for H3N2 and 58% for B strain in the intramuscular group ( p = 0.36 for H1N1, p = 0.02 for H3N2, p p = 0.38). Conclusions Immunogenicity of the 2008–9 influenza vaccine given intradermally or intramuscularly was overall poor in lung transplant recipients. Novel strategies for influenza vaccination in this population are needed.