*Purpose: Patients receiving eculizumab are at a 1,000-2,000-fold increased risk of invasive meningococcal infections. Therefore, the Advisory Committee for Immunization Practices recommends that these patients receive meningococcal vaccination at least 2 weeks prior to the start of therapy. However, despite adequate vaccination, multiple reports of breakthrough meningococcal disease have been reported. Solid organ transplant (SOT) recipients are a unique population with notoriously diminished vaccine response due to chronic immunosuppression, potentially placing them at increased risk for breakthrough meningococcal disease while receiving eculizumab. Therefore, the purpose of this study is to evaluate meningococcal vaccine response in this patient population.

*Methods: This is a single-center, retrospective evaluation of all solid organ transplant recipients 18 years of age or older that underwent eculizumab therapy between January 1, 2014 and June 1, 2020. All patients that received both doses of the meningococcal vaccines and had subsequent N. meningitidis IgG concentrations available within 6 months of vaccination were included. The primary outcome was the meningococcal vaccine response rate, which was measured using N. meningitidis IgG concentrations against serogroups A, C, Y, and W-135.

*Results: A total of 17 patients met the pre-specified inclusion criteria and was primarily composed of lung transplant recipients. Preliminary results indicated that N. meningitidis IgG serologic response occurred in only 41.2% of patients against serogroup A, 58.8% against serogroup C, 47.0% against group Y, and 70.6% to serogroup W-135 following vaccination. Further results to follow.

*Conclusions: Meningococcal IgG vaccine response varied against the different meningococcal serogroups. Consideration should be given towards repeat vaccination and prolonged antimicrobial prophylaxis in vaccine non-responders undergoing eculizumab therapy.

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