Randomized clinical trial to assess the protective efficacy of a Plasmodium vivax CS synthetic vaccine

This is the authors' abstract. We don't add key points for this paper.

A randomized, double-blind, controlled clinical trial was conducted to assess the safety and protective efficacy of the Plasmodium vivax circumsporozoite (CS) protein. A total of 35 healthy adults, either malaria-naïve (n = 17) or P.vivax semi-immune (n = 18), were enrolled and immunized intramuscularly (i.m.) at months 0, 2, and 6, with the Pv CS (150 µg) formulated in Montanide ISA-51 adjuvant. Most volunteers developed Pv CS specific antibody and T-cell responses and were subjected to a P. vivax sporozoite controlled human malaria infection (CHMI) 30 days after the last immunization. Sterile protection was observed in five of 11 naïve (42%) and four of 11 semi-immune (36%) volunteers by showing no parasitemia during the 60 days follow-up, as did a semi-immune control (1/5) volunteer. All non-protected volunteers developed malaria symptoms 10–19 days after CHMI and were immediately treated with antimalarial drugs. This is the first study of a P. vivax sub-unit vaccine demonstrating sterile protection against P. vivax infection.