- Bastiaens, Guido JH;
- van Meer, Maurits PA;
- Scholzen, Anja;
- Obiero, Joshua M;
- Vatanshenassan, Mansoureh;
- van Grinsven, Tim;
- Sim, B Kim Lee;
- Billingsley, Peter F;
- James, Eric R;
- Gunasekera, Anusha;
- Bijker, Else M;
- van Gemert, Geert-Jan;
- van de Vegte-Bolmer, Marga;
- Graumans, Wouter;
- Hermsen, Cornelus C;
- de Mast, Quirijn;
- van der Ven, André JAM;
- Hoffman, Stephen L;
- Sauerwein, Robert W
Immunization of volunteers under chloroquine prophylaxis by bites of Plasmodium falciparum sporozoite (PfSPZ)-infected mosquitoes induces > 90% protection against controlled human malaria infection (CHMI). We studied intradermal immunization with cryopreserved, infectious PfSPZ in volunteers taking chloroquine (PfSPZ chemoprophylaxis vaccine [CVac]). Vaccine groups 1 and 3 received 3× monthly immunizations with 7.5 × 10(4) PfSPZ. Control groups 2 and 4 received normal saline. Groups 1 and 2 underwent CHMI (#1) by mosquito bite 60 days after the third immunization. Groups 3 and 4 were boosted 168 days after the third immunization and underwent CHMI (#2) 137 days later. Vaccinees (11/20, 55%) and controls (6/10, 60%) had the same percentage of mild to moderate solicited adverse events. After CHMI #1, 8/10 vaccinees (group 1) and 5/5 controls (group 2) became parasitemic by microscopy; the two negatives were positive by quantitative real-time polymerase chain reaction (qPCR). After CHMI #2, all vaccinees in group 3 and controls in group 4 were parasitemic by qPCR. Vaccinees showed weak antibody and no detectable cellular immune responses. Intradermal immunization with up to 3 × 10(5) PfSPZ-CVac was safe, but induced only minimal immune responses and no sterile protection against Pf CHMI.