Immunogenicity and safety of double versus standard dose of the seasonal influenza vaccine in solid-organ transplant recipients: A randomized controlled trial

Background: The use of vaccines with higher doses of antigen is an attractive strategy to improve the immunogenicity of influenza vaccination in transplant recipients. However, the effect of vaccination with a double-dose (DD) containing 30 µg of antigen in this population remains unknown.

Methods: We performed a randomized controlled trial to compare the immunogenicity and safety of DD (30 µg) vs. standard dose (SD, 15 µg) of a trivalent inactivated influenza vaccine in kidney and liver transplant recipients. Immunogenicity was assessed by hemagglutination-inhibition assay. Vaccine response was defined as seroconversion to at least one viral strain 2 weeks after vaccination and seroprotection as a titer ≥40.

Results: Sixty-three kidney and 16 liver transplant recipients were enrolled. Forty patients received the DD and 39 the SD vaccine. Overall, 40% of patients in the DD compared to 26% in the SD group (P = 0.174) responded to vaccine. In the DD arm, more patients were seroprotected to all viral strains after vaccination (88% vs 69%, P = 0.048). Post vaccination geometric mean titers of antibodies were 131.9 vs. 89.7 (P = 0.187) for H1N1, 185.4 vs. 138.7 (P = 0.182) for H3N2, and 96.6 vs. 68.8 (P = 0.081) for influenza B with the DD vs. SD. In both groups, most of the adverse events were mild and no vaccine-related severe adverse events were observed.

Conclusion: Double-dose influenza vaccine is safe and may increase antibody response in transplant recipients. In this population, DD vaccination could be an alternative when high-dose vaccine is not available. NCT02746783.