At least 2 weeks before the bone marrow infusion, the patient will be immunized with Prevnar 7. Prevnar 7 is a vaccine that is used in children to protect against some types of bacteria called Streptococcus pneumoniae, which can cause the lung infection called pneumonia. People with Sickle Cell anemia are at a higher risk of dying from an infection from this type of bacteria. Although children are regularly given the Prevnar 7 vaccine, it is not common to test a child's immune response to the vaccine. In this study, we will check the immune system's response to the vaccine by drawing an extra 3 mL (less than 1 teaspoon) of blood 3 weeks after the patient gets the Prevnar 7 vaccine.