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.
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 < 0.01 for B). Mild adverse events were seen in 44 % of patients in the intradermal group and 34 % in the intramuscular group (p = 0.38).
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.