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NCT Number: NCT07194668

R21/MM Dosing, Presentations, and Preservatives

This is a single blind randomised controlled trial (Phase 3 trial). This study aims to assess whether a half-dose of the R21/Matrix-M malaria vaccine is as effective as the full dose in children and adults. The results will help optimize vaccine usage and improve malaria prevention strategies.

All participants will receive the same number of injections and will be randomly assigned to receive one of the followings:

* Group 1: Adults and adolescents receiving the standard adult vaccine dose: 10μg R21/50μg Matrix-M (n=125). * Group 2: Adults and adolescents receiving a half of the standard adult vaccine dose: 5μg R21/50μg Matrix-M: 10 dose vials with adaptor Preservative Free (n=125) * Group 3: Adults and adolescents receiving a half of the standard adult vaccine dose: 5μg R21/50μg Matrix-M: 10 dose vials with 2PE Preservative (n=125)

Clinical procedure for participants:

* Standardized symptom questionnaire * Physical examination:

Weight, height, pulse, blood pressure, respiratory rate, tympanic temperature. Spleen and liver size will be recorded if palpable. Pregnancy test (for female of child bearing potential)

* Venous blood collection (Pre-vaccination) 3mL * Vaccination

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Key information

Conditions

Plasmodium Falciparum Malaria Infections Malaria Malaria, Falciparum Mosquito-Borne Diseases Parasitic Diseases Protozoan Infections Vaccine Reaction Vector Borne Diseases

Age range

14 year–60 year

Sex eligibility

All sexes

Study type

Interventional

Phase

Phase 4

Primary location

Lama Upazila Health Complex, Lāma, Lama, Bangladesh

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About this study

This study was funded by Hanako Foundation. The grant reference number: 001/2026.

Who can participate

Healthy volunteers accepted: Yes

Only the study team can determine whether someone qualifies for participation.

Inclusion criteria

  • Residence in a study village for the study period, i.e. 12 months.
  • Age 14 years to 60 years.
  • Written informed consent/assent provided by participants (or a parent/guardian in case the participant is under 18 years old).

Exclusion criteria

  • Pregnancy, plan to get pregnant within one month of vaccination, or breastfeeding.
  • Acute illness requiring intervention.
  • A history of an adverse reaction to study vaccine.
  • Prior receipt of any other malaria vaccine.
  • Enrolment in another intervention trial in the last month.
  • Planned enrolment in another intervention trial in the coming 12 months.
  • Regular use of Immunomodulating drugs e.g, Steroid, Methotrexate, Immunotherapy etc. in the past month and/or planned for the coming 12 months.

Treatment and study plan

10μg R21/50μg Matrix-M

Biological

Adults and adolescents receiving the standard adult vaccine dose: 10μg R21/50μg Matrix-M (n=125)

5μg R21/50μg Matrix-M with adaptor preservative free

Biological

Adults and adolescents receiving a half of the standard adult vaccine dose: 5μg R21/50μg Matrix-M using two presentations: 10 dose vials with adaptor Preservative Free (n=125)

5μg R21/50μg Matrix-M with 2PE preservative

Biological

Adults and adolescents receiving a half of the standard adult vaccine dose: 5μg R21/50μg Matrix-M using two presentations: 10 dose vials with 2PE Preservative (n=125)

Primary outcomes

  1. The concentration of antibodies against Plasmodium falciparum circumsporozoite (anti-NANP total IgG antibody)

    Time frame: One month after the completion of the third dose (at M3), and one month after the booster dose (at M12).

  2. The concentration of antibodies against Plasmodium falciparum circumsporozoite (anti C-Term, and full length R21 total IgG antibody), in addition to total IgG against Hepatitis B surface antigen

    Time frame: One month after the completion of the third dose (at M3), and one month after the booster dose (at M12).

Secondary outcomes

  1. Adverse event and severe adverse event reports for safety and tolerability assessment of the standard adult vaccine dose 10μg R21/50μg Matrix-M and a half of the standard adult dose 5μg R21/50μg Matrix-M

    Time frame: At Month 1, Month 2, Month 3, Month 11 and Month 12

  2. Adverse event and severe adverse event reports for safety and tolerability assessment a half of the standard adult dose 5μg R21/50μg Matrix-M with 2PE preservative vs, without 2PE preservative.

    Time frame: At Month 1, Month 2, Month 3, Month 11 and Month 12

Other outcomes

  1. Prevalence and level of vaccine-induced antibodies.

    Time frame: At Month 0, Month 3, Month 11 and Month 12

  2. Prevalence and level of immunity to malaria and immunological responsiveness that may be relevant to prior malaria exposure and be used to predict vaccine immunogenicity.

    Time frame: At Month 0, Month 3, Month 11 and Month 12

  3. Prevalence and level of other factors affecting vaccine immunogenicity, such as antibodies against viral pathogens including cytomegalovirus.

    Time frame: At Month 0, Month 3, Month 11 and Month 12

Study contacts

Contact information is provided by the study sponsor or research team.

Lorenz von Seidlein

CONTACT

[email protected]

+66926486322

Rupam Tripura

CONTACT

[email protected]

+8801572288558

Sponsors and collaborators

Lead sponsor

University of Oxford

Other

Registry information

Official study title

Immunogenicity of a Fractional Adult Dose of the Malaria Vaccine R21/Matrix-M - A Noninferiority Trial

Acronym: VAC100

Important dates

Study start
2026
Primary completion
2026
Study completion
2026
First posted
Sep 26, 2025
Registry last updated
Mar 16, 2026

OpenTrials presents study information sourced from ClinicalTrials.gov. The official registry record should be consulted for the latest information.

View the official ClinicalTrials.gov record (opens in a new tab)

This listing is for discovery and informational purposes only. It is not medical advice, does not guarantee that a study is recruiting, and does not determine eligibility. Contact the study team and a qualified healthcare professional when considering participation.

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