sentences:  The EWOG-MDS JMML study allows each child's physician to determine whether or not a splenectomy should be done, and large spleens are commonly removed prior to bone marrow transplant.When a splenectomy is scheduled, JMML patients are advised to receive vaccines against "Streptococcus pneumoniae" and "Haemophilus influenza" at least 2 weeks prior to the procedure.Following splenectomy, penicillin may be administered daily in order to protect the patient against bacterial infections that the spleen would otherwise have protected against; this daily preventative regimen will often continue indefinitely.