Research Trial Assessing the Immunogenicity and Safety of Three Meningococcal B Vaccine Strategies Among Patients With Asplenia.

Currently, in France, no immunogenicity data on Meningococcal B vaccines, neither with Bexsero® nor with Trumenba®, are available in asplenic patients, population at high risk of infection.

As asplenic individuals (all causes) show less optimal immune response to conjugate meningococcal C vaccine compared to matched controls. [4], we hypothesize that a similar less optimal response may be expected for MenB vaccines among asplenic subjects. .

That is why, we proposed in this study to evaluate two reinforced strategies with 3 administrations (M0, M1, and M6) of Bexsero® or Trumenba ®. Moreover, the study will also allow exploring the persistence of the immune response in this population. Indeed, few data are available on this persistence in the general population.

Inclusion criteria

• Male or female, >=18 to <=75 years old.
• Asplenic patient (for at least 2 weeks) with Howell Jolly bodies visible on blood film
• Splenectomy confirmed by consultation and/or hospitalization report or the ultrasound if it has been performed during the routine follow-up
• Women of childbearing age must have an effective contraception during the first 9 months of the study.
• Participants must give written consent prior to any trial procedure
• Participants must be covered by social security regimen or equivalent.
• Participants will be followed during the 4 years from the inclusion visit.

Exclusion criteria

• History of meningococcal vaccination B.
• History of anaphylaxis post vaccination.
• Known allergy to any components (active substances or excipients) of both vaccines.
• Patients who cannot stop antibiotics 3 days before blood collection.
• Participants who have received any another vaccines within 4 weeks prior to immunization or who are planning to receive any vaccine within the first 7 months of the study (except the meningococcal ACWY vaccine, the anti-pneumococcal vaccine, the Haemophilus influenzae type B vaccine, the anti-Covid-19 vaccine), annual influenza vaccination which is permitted 2 weeks before and after each vaccination visit of the study and then allowed at any time during the study follow up).
• Parenteral Ig within the 3 months prior to VS or planned during the study.
• Chemotherapy agents within 6 months prior M0 or planning to take any during the study.
• Steroids (> 10mg/day; > 14 days) within the month preceding M0 or planning to take any during the study.
• Any pathology or condition that may impair the immune response, apart from splenectomy: immunosuppressive therapy in progress or in the 6 months prior to inclusion, hematopoietic stem cells allo / autograft, primary immunodeficiency, nephrotic syndrome, evolutive cancer, cirrhosis, known infection to HIV;
• Thrombocytopenia or any coagulation disorder contra-indicating intramuscularly injections.
• Pregnancy, breastfeeding or positive pregnancy test up to 7 months after inclusion.
• Severe acute febrile illness within the week before inclusion.
• Registration for any other clinical trial throughout the trial period except observational study.