Booster Vaccination Against Invasive Pneumococcal Disease and Hepatitis B in Previously Vaccinated Solid Organ Transplant Recipients Without Seroprotection

Background: Despite pre-transplantation vaccination against invasive pneumococcal disease (IPD) and hepatitis B virus (HBV), most solid organ transplant (SOT) recipients are without post-transplantation seroprotection against IPD and HBV. We aimed to determine the seroprotection rates and changes in antibody concentrations after booster vaccination against IPD and HBV in SOT recipients without post-transplantation seroprotection after pre-transplantation vaccination. Furthermore, we aimed to identify risk factors associated with non-response to booster vaccination. Methods: In this prospective cohort study, we included adult SOT recipients without post-transplantation seroprotection against IPD who then received the 23-valent pneumococcal polysaccharide vaccine (PPSV23) booster, as well as adult SOT recipients without seroprotection against HBV who then received the Engerix-B^® booster after pre-transplantation vaccination. Logistic regression models were used to analyze risk factors for non-response to booster vaccination. Results: We included 50 SOT recipients in analyses of booster vaccination against IPD and 52 SOT recipients in analyses of booster vaccination against HBV. Seroprotection rates were 52% after booster vaccination against IPD and 7.7% after booster vaccination against HBV. The median geometric mean concentration of pneumococcal antibodies increased from 0.54 µg/mL IgG (interquartile range, IQR: 0.35–0.77) to 1.21 µg/mL IgG (IQR: 0.87–1.62) after booster vaccination (p < 0.001). Having pre-transplantation seroprotection against IPD at time of listing was associated with lower odds of non-response to booster vaccination. We were not able to identify risk factors for non-response to HBV booster vaccination. Conclusions: Booster vaccination improved seroprotection against IPD, but not HBV. Further studies are needed to examine optimal vaccination strategies for SOT recipients.