Antibody response to influenza immunization in patients after heart transplantation

The aim of this study was to evaluate post-heart transplantation (Htx) response to two-dose and three-dose influenza vaccine. Hemagglutination inhibition antibodies were monitored in HTx recipients immunized twice (n = 25) or three times (n = 17), and non-HTx controls (n = 8) once, with inactivated influenza vaccine, Post-first dose protective antibody titers (≤1:40) were demonstrated in 9/25 (36%) for A/Singapore/(H₁N₁), 5/25 (20%) for A/Shanghai/(H₃N₂) and 2/25 (8%) for B/Yamagata compared with 4/8 (50%), 6/8 (75%) and 2/8 (25%), respectively, for controls. Post-second dose protective titers remained low, increasing following the third dose to 71%, 65% and 29%, respectively. The abnormally low antibody responses of HTx recipients to one-dose and two-dose influenza vaccine can be overcome by a third dose.