Deficient Long-Term Response to Pandemic Vaccine Results in An Insufficient Antibody Response to Seasonal Influenza Vaccination in Solid Organ Transplant Recipients

Background. Little is known about the long-term antibody response to the 2009-H1N1 vaccine in solid organ transplant recipients (SOTR) and its clinical repercussion on the efficacy of following 2010-2011 influenza vaccine. Methods. We performed a multicenter prospective study in SOTR receiving one dose of the nonadjuvant 2010-2011 seasonal influenza vaccine and determined the immunological response at 5 weeks after vaccination. Results. One hundred SOTR were included. Long-term antibody titers to the previous vaccine were only detected in one third of the patients. Patients with baseline titers had significantly higher seroprotection for the 2009-H1N1 strain (100% vs. 73%, relative risks [RR] 1.37, 95% confidence intervals [CI] 1.19-1.57; P = 0.006), for H3N2 strain (100% vs. 62.2%, RR 1.61, 95% CI 1.36-1.90; P = 0.005), and for B strain (100% vs. 69%; P = 0.02). The seroconversion rate in patients with baseline titers was 90.9% vs. 73% (RR 2.97, 95% CI 0.75-11.74; P = 0.07) for the 2009-H1N1 strain, 92.2% vs. 62.2% (RR 5.29, 95% CI 0.8-35.7; P = 0.02) for the H3N2 strain, and 58.3% vs. 69% (P = 0.45) for the B strain. Conclusions. SOTR response to the 2010-2011 influenza vaccine was not optimal. The response was related to baseline titers; however, most of the patients did not exhibit detectable antibodies at vaccination lacking long-term response. New strategies are necessary to improve vaccination efficacy.