This is an age de-escalation, dose-escalation open label randomised trial studying the safety and immunogenicity of RH5.1/Matrix-M, administered intramuscularly in healthy adults, young children and infants in Tanzania

A total of 60 participants will be enrolled consisting of healthy adults (18-45 years) and infants (5-17 months) residing in Bagamoyo district, Tanzania. Participants will be recruited from areas of low malaria transmission in Bagamoyo town and areas of high malaria transmission within Bagamoyo district. All participants will be followed for 2-2.5years after the first vaccination with RH5.1/Matrix-M vaccination. The duration of the entire study will be 2-2.5years per participant from the time of first vaccination.

The trial is funded by EDCTP (reference: RIA2016V-1649 MMVC).

The paper containing this trial's results is available at: https://www.thelancet.com/journals/laninf/article/PIIS1473-3099(24)00312-8/fulltext

Inclusion Criteria:

• Group 1: Healthy male or female adults aged 18-45 years at the time of enrolment with signed consent.
• Group 1 (Female only participants): Must be non-pregnant (as demonstrated by a negative urine pregnancy test), and practice continuous effective contraception* for the duration of the study. (Female volunteers are required to use an effective form of contraception during the course of the study as this is a Phase I, study and there is currently no information about the effect of this vaccine on a foetus. Acceptable forms of contraception for female volunteers include:
• Established use of oral, injected or implanted hormonal methods of contraception.
• Placement of an intrauterine device (IUD) or intrauterine system (IUS).
• Total abdominal hysterectomy.
• Groups 2a, 2b, 2c & 2d: Healthy male or female infants aged 5-17 months at the time of enrolment with signed consent obtained from parents or guardians.
• Planned long-term (at least 24 months from the date of recruitment) or permanent residence in the study area.
• Adults with a Body Mass Index (BMI) 18 to 30 Kg/m2; or infants with Z-score of weight- for-age within ±2SD.

Exclusion Criteria:

• Clinically significant congenital abnormalities as judged by the PI or other delegated individual.
• Clinically significant history of skin disorder (psoriasis, contact dermatitis etc.), allergy, cardiovascular disease, respiratory disease, endocrine disorder, liver disease, renal disease, gastrointestinal disease and neurological illness as judged by the PI or other delegated individual.
• 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).
• History of cancer (except basal cell carcinoma of the skin and cervical carcinoma in situ).
• Weight for age z-scores below 2 standard deviations of normal for age.
• History of allergic disease or reactions likely to be exacerbated by any component of the vaccines, e.g. egg products, Kathon, neomycin, betapropiolactone.
• Any history of anaphylaxis in relation to vaccination.
• Clinically significant laboratory abnormality as judged by the PI or other delegated individual.
• Blood transfusion within one month of enrolment.
• History of vaccination with previous experimental malaria vaccines.
• 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).
• Any other finding which in the opinion of the PI or other delegated individual would increase the risk of an adverse outcome from participation in the trial.
• Likelihood of travel away from the study area.
• Positive malaria by blood smear at screening.
• Female participant who is pregnant, lactating or planning pregnancy during the course of the trial.
• Scheduled elective surgery or other procedures requiring general anaesthesia during the trial.
• Any other 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.

Study information will be made available through a repository. The information to be made available will be anonymized so that there is no link to participants and will include data on safety, immune responses and any other data generated from samples obtained in this study.

After publication of manuscripts related to the trial and for a minimum of 15 years from the end of the trial.

Anonymized participant data will be made available when the trial is complete, upon requests directed to a corresponding author. Proposals will be reviewed and approved by the sponsor, investigators, and collaborators on the basis of scientific merit. After approval of a proposal, data can be shared through the secure online repository.