A Phase II Clinical Study to Assess the Safety, Immunogenicity, and Efficacy of Blood-stage Plasmodium Vivax Malaria Vaccine Candidate PvRII/Matrix-M in Healthy Thai Adults Living in Thailand

This study will recruit up to 36 eligible healthy volunteers aged 20-55 in Thailand at the Faculty of Tropical Medicine, Mahidol University. Eighteen volunteers will receive three doses of the PvRII/Matrix-M candidate vaccine, and 18 volunteers will receive three doses of the placebo vaccine. Safety and immunogenicity will be evaluated after each dose as per protocol. Approximately four weeks after receiving the third vaccination, 24 volunteers will undergo blood-stage CHMI with Plasmodium vivax. The volunteers will be monitored closely as in-patients in the Hospital for Tropical Diseases and treated according to the Research Proposal Submission Form. This is a randomized controlled single-centre Phase II P. vivax blood-stage CHMI trial to assess the safety, immunogenicity, and efficacy of the candidate malaria vaccine PvRII/Matrix-M.Healthy Thai adults aged between 20 and 55 years will be recruited and randomized at the Faculty of Tropical Medicine, Mahidol University in Bangkok.Vaccination group: Up to 18 healthy adults aged between 20 and 55 years will be recruited. These volunteers will receive three doses of the PvRII/Matrix-M vaccine intramuscularly at months 0, 1, and 6. Approximately three to four weeks post-boost (3rd vaccination), 12 volunteers will undergo P. vivax blood-stage CHMI, induced by injection of P. vivax infected erythrocytes.Control group: Up to 18 healthy adults aged between 20 and 55 years will be recruited. These volunteers will receive three doses of HBV vaccine intramuscularly at months 0, 1, and 6.12 volunteers will undergo P. vivax blood-stage CHMI, induced by injection of P. vivax infected erythrocytes. Volunteers will have blood taken at regular intervals following vaccination and in the post-CHMI period to assess the immune response to vaccination and subsequent challenge, as well as parasite growth dynamics and gametocytaemia. Close monitoring will continue until volunteers meet the criteria for treatment or until 28 days after the challenge, when treatment will be started empirically. Therapy will be with a standard course of chloroquine where not contraindicated. As infection will be induced via intravenous injection of blood-stage parasites, there will be no liver-stage infection and no hypnozoite formation, thereby eliminating the need for radical cure with primaquine therapy. Follow-up at the study site will be up to 1 year after antimalarial treatment.

Study type: Interventional
Enrollment:  36 participants
Primary purpose: Prevention
Allocation: Randomized
Interventional Model: Parallel Assignment
Masking : Triple
NCT number: NCT05380388
Phase: Phase II

P. vivax
Vaccines (Immune Correlates)

Dec 2024 — Dec 2025

Thailand

Towards a vaccine for Plasmodium vivax