Clinical Study to Assess Minimum Mosquito Bites for P. Vivax Infection in Thai Adults

Recruiting now · Not applicable

Conditions studied: Plasmodium Vivax Infection

In brief

This study is a human challenge study to assess the minimum infective mosquito bite dose in a controlled human malaria Infection (via P. vivax sporozites) in healthy volunteers. The results will inform the development of a P. vivax mosquito-delivered CHMI trial platform, supporting safer and more accurate vaccine efficacy assessments. Conducting the trial in individuals genetically and immunologically similar to the target population will also enhance the relevance of findings to real-world endemic settings. This study is funded by the UK Wellcome Trust. The grant reference number are Oxford/MORU: 212336/Z/18/Z and 212336/Z/18/A, and Mahidol University: 212336/A/18/Z and 212336/A/18/A.

Key facts

Study ID

NCT07257965

Run by

University of Oxford

People needed

24

Starts

2026-02-02

Expected to finish

2027-08-31

Last updated by the study team

2026-03-27

Who can join

Age: 20 and older, up to 55. Sex: any. Healthy volunteers: accepted.

You may qualify if…

• Healthy adult aged 20 to 55 years with weight more than 50 kg.
• No recent malaria infection.
• Red blood cells positive for the Duffy antigen/chemokine receptor (DARC).
• CYP2D6 alleles consistent with normal metaboliser status.
• Normal level of Glucose-6-phosphate dehydrogenase (G6PD) enzyme activity by the WHO definition.
• Women only: Must practice continuous effective contraception for the duration of study period until 3 months post-challenge.
• Agreement to refrain from blood donation during the course of the study and for 1 year after the end of their involvement in the study.
• Willing to take a curative antimalarial regimen following challenge.
• Willing to be admitted in the Hospital for Tropical Diseases for clinical monitoring until antimalarial treatment (chloroquine) is completed and their symptoms are settling.
• Willing to reside in Bangkok for the duration of the clinical part of the study, until all antimalarial treatment has been completed.
• Willing to be followed up for 1 year post treatment initiation.
• Reachable (24/7) by mobile phone during the period between challenge CHMI and completion of all antimalarial treatment.
• Able to read and write in Thai and able to answer ALL questions on the informed consent questionnaire correctly.
• Provided written informed consent to participate in the trial.
• Cardiovascular risk assessment is low (less than 10% in the next 10 years according to the cardiovascular risk assessment from Thai NCD Division, DDC, MoPH (2016)
• Educational level: has at least a bachelor's degree.
• The volunteer MUST NOT enter the study if any of the following apply:
• History of clinical malaria.
• Positive malaria PCR OR malaria film OR malaria serology (recent exposure by Multiplex Bead Based Immunoassay)
• History of severe allergy to mosquito bite
• G6PD mutation
• Presence of any medical condition (either physical or psychological) which in the judgment of the investigator would place the participant at undue risk or interfere with the results of the study (e.g. serious underlying cardiac, renal, hepatic or neurological disease; severe malnutrition; congenital defects or febrile condition)
• Presence of chronic disease or chronically use of medication.
• Plan to travel outside of Bangkok within the period of challenge until 3 months after.
• Use of systemic antibiotics with known antimalarial activity in the 30 days before challenge (e.g. trimethoprim-sulfamethoxazole, doxycycline, tetracycline, clindamycin, erythromycin, fluoroquinolones and azithromycin).

Where it is running

• Faculty of Tropical Medicine, Mahidol University — Bangkok, Thailand (enrolling)

Full record on ClinicalTrials.gov

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