In 2017, a new regulation introduced the quadrivalent meningococcal conjugate vaccine (MenACWY) for mandatory immunization individuals with anatomical or functional asplenia (e.g., splenectomy, sickle cell anemia), complement deficiencies (C5–C9), or those undergoing hematopoietic stem cell transplantation. The gene discussed is C5; the disease is familial isolated congenital asplenia.