There has been substantial progress in the control of malaria during the past decade but it is estimated that in 2015 there were still 429,000 (uncertainty interval 235-639,000) deaths from malaria, mainly in African children, 1 and current gains are threatened by the emergence of artemisinin and insecticide resistance. New tools, including malaria vaccines, are needed. The malaria vaccine RTS, S/AS01 has so far attracted the most attention, as it is the first malaria vaccine to obtain a positive approval from a regulatory authority 2 following a long period of development and evaluation. 3 However, during this period, substantial progress has been made with the development of several other malaria vaccines, including the Plasmodium falciparum sporozoite vaccine PfSPZ.

In this edition of Lancet Infectious Diseases Sissoko, Healy and colleagues report the results of one of the first efficacy trials of this vaccine undertaken in a malaria endemic country. 4 The development of PfSPZ has been based on the observation made in the 1970s that immunisation with irradiated sporozoites, delivered through the bites of over 1,000 infected mosquitoes, provided protection against challenge from a mosquito infected with viable sporozoites. 5 Irradiated sporozoites undergo partial development in liver cells to form a schizont, which induces an immune response, but which dies before rupturing into the blood stream and releasing the blood stage parasites which cause symptoms. Development of a vaccine based on irradiated sporozoites was for many years considered to be impractical because of the need for delivery by mosquito bite and a requirement to store the vaccine at a very low temperature. However, with courage and persistence, Hoffman and his colleagues at Sanaria have overcome these challenges by developing novel methods