Malaria is caused by a parasite that is transmitted by certain types of mosquitoes. Despite various prevention efforts from insecticide-treated bed nets to disease-preventing medications malaria continues to exact a huge toll. The World Health Organization approved the first-ever malaria vaccine, for use in young children. The vaccine, called Mosquirix, is given in three doses between the ages of 5 and 17 months, with a fourth dose about 18 months later. While the vaccine was welcomed as a breakthrough, it is not a home run. Lab engineered antibody protected most participants from infection with the malaria parasite. Why has been so hard to develop an effective vaccine?