The Centers for Disease Control and Prevention endorses these vaccines for persons with asplenia: http://www.immunize.org/catg.d/p4047.pdf[8]
CureSearch for Children's Cancer has published a wallet card that one can print out and carry. The card indicates the risk; need for medical attention to include parenteral antibiotics when a fever is 101°F; and suggested management: http://www.survivorshipguidelines.org/pdf/SplenicPrecautions.pdf (p.4)