1 Shoklo Malaria Research Unit (SMRU), PO Box 46, Mae Sot, Tak 63110 Thailand.
2 Aide Médicale Internationale (AMI), Mae Sot, Tak Thailand.
3 Shoklo Malaria Research Unit (SMRU), PO Box 46, Mae Sot, Tak 63110 Thailand ; Mahidol-Oxford Tropical Medicine Research Unit (MORU), Mahidol University, Bangkok, 10400 Thailand ; Centre for Clinical Vaccinology and Tropical Medicine, Churchill Hospital, Oxford, OX3 7LJ UK.