a study to determine if new types of malaria vaccines are safe, effective and lead to immunity in kenyan adults

Conditions: Malaria,Falciparum

Summary: this is a phase iib clinical trial in malaria-exposed individuals to assess the immunogenicity, safety and efficacy of the two vaccines in the context of controlled human malaria infection, p. falciparum sporozoite challenge (pfspz challenge).

a total of 64 participants will be enrolled for challenge and divided into four groups as follows: * 20 participants to receive r21/matrix m (r21/mm) with intradermal pfspz challenge; * 20 participants to receive viral-vectored me-trap with intradermal pfspz challenge; * 10 participants to receive r21/mm with direct venous inoculation pfspz challenge; and * 14 participants comprising of the control group with intradermal pfspz challenge. blood tests and clinical assessments will be conducted to screen out participants with health conditions that may impact participation in the study.

Eligibility criteria:
inclusion criteria: * healthy adults aged 18 to 45 years * able and willing (in the investigator's opinion) to comply with all study requirements * non-pregnant, non-lactating adult female or adult male * agreement to refrain from blood donation during the study * use of effective method of contraception for the duration of study for female participants. for those with no contraception, they will be referred for contraception at the relevant health facility. for female participants, we will ask them to attend with their family planning records for verification. effective contraception is defined as a contraceptive method with failure rate of less than 1% per year when used consistently and correctly, in accordance with the product label. examples of these include: combined oral contraceptives; injectable progestogen; implants of etenogestrel or levonorgestrel; intrauterine device or intrauterine system; male condom combined with a vaginal spermicide (foam, gel, film, cream or suppository); and male condom combined with a female diaphragm, either with or without a vaginal spermicide (foam, gel, film, cream, or suppository) * provide written informed consent * plan to remain resident in the study area for 1 year following first dose of vaccination exclusion criteria: * clinically significant congenital abnormalities as judged by the study clinicians * any confirmed or suspected immunosuppressive or immunodeficient state, including hiv infection; asplenia; recurrent, severe infections and chronic (more than 14 days) immunosuppressant medication within the past 6 months (inhaled and topical steroids are allowed). * sickle cell disease * any history of anaphylaxis in relation to vaccination * clinically significant laboratory abnormality as judged by the study clinician * blood transfusion within one month of enrolment * haemoglobin less than 11.3 g/dl for men and less than 10g/dl for in women, where judged to be clinically significant in the opinion of the investigator. * administration of immunoglobulins and/or any blood products within the three months preceding the planned administration of the vaccine candidate * participation in another research study involving receipt of an investigational product in the 30 days preceding enrolment, or planned use during the study period * seropositive for hepatitis b surface antigen (hbsag) or hepatitis c (hcv igg) * use of systemic antibiotics with known antimalarial activity within 30 days of administration of pfspz challenge (e.g. trimethoprim-sulfamethoxazole, doxycycline, tetracycline, clindamycin, erythromycin, fluoroquinolones and azithromycin) * women only; pregnancy, or an intention to become pregnant a day before challenge i.e. at c-1 * any significant disease, disorder or situation which, in the opinion of the investigator, may either put the participants at risk because of participation in the trial, or may influence the result of the trial, or the participant's ability to participate in the trial * confirmed parasite positive by pcr a day before challenge i.e. at c-1.