In the EHMI-8 study (CMO 2006/207) the investigators induced sterile protection against P. falciparum challenge in healthy Dutch volunteers by repeated exposure to infected mosquitoes whilst under chloroquine prophylaxis. The surprisingly efficient induction of protection in this study strongly supports the development of whole parasite vaccines and is therefore an important finding to malaria vaccine development. In this study (EHMI8B) the investigators would like to explore the longevity of the protective immune response and simultaneously further characterise immune mechanisms responsible for protection by re-exposing EHMI-8 volunteers to infected mosquito bites.