This is a clinical trial to evaluate the safety and immunogenicity of R21/MM in healthy Kenyan participants from the different age groups.Participants will receive 3 vaccinations 4 weeks apart.

The study includes three age groups:

Group 1: healthy adults (18-45 years) Group 2: young children (aged 1-5 years) Group 3: infants (aged 5- <12 months of age) Each group will receive 3 vaccine doses which will be 4-weeks apart. A booster dose will be administered at 9-25 months post 3rd dose.

The trial is funded by The European & Developing Countries Clinical Trials Partnership (EDCTP), European Union, ref: RIA2016V-1649 MMVC

Inclusion Criteria:

• Healthy adults aged 18 to 45 years (Group 1), Healthy child aged 1-5 years (Group 2), healthy infant aged 5- <12 months (Group 3)
• 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 duration of study for female participants.

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 partner sterilisation at least 6 months prior to the female subject's entry into the study, and the relationship is monogamous; 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)

• Adults with a Body Mass Index (BMI) 18 to 30 Kg/m2; or young children and infants with Z-score of weight-for-age within ±2SD
• Provide written informed consent
• Plan to remain resident in the study area for 2 years following last dose of vaccination

Exclusion Criteria:

• Clinically significant congenital abnormalities as judged by the study clinician.
• 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 trait or disease or G6PD deficiency.
• 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.
• 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 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.