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. 2023 Oct 12:8:450.
doi: 10.12688/wellcomeopenres.19795.1. eCollection 2023.

Safety and immunogenicity of varied doses of R21/Matrix-M™ vaccine at three years follow-up: A phase 1b age de-escalation, dose-escalation trial in adults, children, and infants in Kilifi-Kenya

Samuel Sang  1 , Mehreen S Datoo  2 , Edward Otieno  1 , Charles Muiruri  1 , Duncan Bellamy  3 , Emmaloise Gathuri  1 , Omar Ngoto  1 , Janet Musembi  1 , Sam Provstgaard-Morys  3 , Lisa Stockdale  3 , Jeremy Aboagye  3 , Daniel Woods  3 , Alison Lawrie  2 , Racheal Roberts  2 , Kelvias Keter  1 , Domtila Kimani  1 , Francis Ndungu  1   4 , Melissa Kapulu  1   4 , Irene Njau  1 , Benedict Orindi  1 , Katie J Ewer  3 , Adrian V S Hill  2   3 , Philip Bejon  1   4 , Mainga Hamaluba  1   4
Affiliations

Safety and immunogenicity of varied doses of R21/Matrix-M™ vaccine at three years follow-up: A phase 1b age de-escalation, dose-escalation trial in adults, children, and infants in Kilifi-Kenya

Samuel Sang et al. Wellcome Open Res. .

Abstract

Background: Falciparum malaria remains a global health problem. Two vaccines, based on the circumsporozoite antigen, are available. RTS, S/AS01 was recommended for use in 2021 following the advice of the World Health Organisation (WHO) Strategic Advisory Group of Experts (SAGE) on Immunization and WHO Malaria Policy Advisory Group (MPAG). It has since been pre-qualified in 2022 by the WHO. R21 is similar to RTS, S/AS01, and recently licensed in Nigeria, Ghana and Burkina Faso following Phase 3 trial results.

Methods: We conducted a Phase 1b age de-escalation, dose escalation bridging study after a change in the manufacturing process for R21. We recruited healthy adults and children and used a three dose primary vaccination series with a booster dose at 1-2 years. Variable doses of R21 and adjuvant (Matrix-M ™) were administered at 10µgR21/50 µg Matrix-M™, 5µgR21/25µg Matrix-M™ and 5µgR21/50µg Matrix-M™ to 20 adults, 20 children, and 51 infants.

Results: Self-limiting adverse events were reported relating to the injection site and mild systemic symptoms. Two serious adverse events were reported, neither linked to vaccination. High levels of IgG antibodies to the circumsporozoite antigen were induced, and geometric mean titres in infants, the target group, were 1.1 (0.9 to 1.3) EU/mL at day 0, 10175 (7724 to 13404) EU/mL at day 84 and (following a booster dose at day 421) 6792 (5310 to 8687) EU/mL at day 456.

Conclusion: R21/Matrix-M™ is safe, and immunogenic when given at varied doses with the peak immune response seen in infants 28 days after a three dose primary vaccination series given four weeks apart. Antibody responses were restored 28 days after a 4 th dose given one year post a three dose primary series in the young children and infants.

Registration: Clinicaltrials.gov (NCT03580824; 9 th of July 2018; Pan African Clinical Trials Registry (PACTR202105682956280; 17 th May 2021).

Keywords: Adults; CSP; Kenya; Matrix-M™; R21; age de-escalation; children; dose escalation; falciparum; immunogenicity; infants; safety.

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Conflict of interest statement

Competing interests: AVSH and KJE are named as coinventors on patent applications related to R21. No competing interests were disclosed for other authors.

Figures

Figure 1.
Figure 1.. Study profile [CONSORT diagram].
Figure 2.
Figure 2.. Geometric mean for NANP IgG antibody titres by age at dose administered.
See this image and copyright information in PMC

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