Prior to progression to Clinical Development Phase III, GlaxoSmithKline Biologicals performed a pooled analysis of phase two safety data following administration of 8,860 doses of RTS,S/AS to 2,981 children under 5 years old. RTS,S/AS was associated with increased rates of non-serious URTI, rash and diaper dermatitis graded mild or moderate. There was no significant increased rate of overall or single SAEs. Two episodes of simple febrile seizure were estimated to be related to vaccination. Significant decreased relative risks of death, any SAE, any SAE excluding malaria- and pneumonia were observed. The results suggest a favorable risk-benefit balance which is to be confirmed in the ongoing Phase III trials.