Patients with SCD are at higher risk of infections and prophylactic vaccination is strongly recommended. Recent data suggest that vaccinal response to pneumococcal antigens in SCD patients is identical to healthy control while controversy concern the stability of the immune protection after vaccination of SCD patient. Antibody levels declined over the year and the need for more frequent vaccination in SCD patient should be investigated. Currently, there is no evidence whether HU may interfere with pneumococcal immune response. Purohit showed that immune response to inactivated influenza A (H1N1) virus vaccine was altered in patient with SCD receiving CT but little is known on immune response to vaccination in patients with SCD receiving HU.