Vaccine Info

RH5.1/AS01 Malaria Vaccine

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Last reviewed
August 6, 2021
Fact checked by
Robert Carlson, MD

RH5.1/AS01 Malaria Vaccine Description

RH5.1/AS01 is a novel, recombinant malaria antigen developed at the University of Oxford.

RH5.1/AS01 is based on recombinant RH5.1 protein produced in the ExpreS2 platform using Drosophila Schneider 2 (S2) cells. RH5.1 is a part of a larger protein complex expressed by the malaria parasite during infection, helping it to invade red blood cells and causing the disease.

The RH5.1 vaccine is intended to block red blood cell invasion and thus the progression of the disease.

The vaccine in the VAC063 study is formulated in the AS01B adjuvant, a liposome-based vaccine adjuvant system used to improve vaccine immunogenicity and efficacy. 

RH5.1/AS01 Malaria Vaccine Indication

RH5.1/AS01 is indicated to prevent the pathogenic blood-stage infection of human malaria. Malaria is a mosquito-borne disease caused by a parasite. 

RH5.1/AS01 Malaria Vaccine News

April 21, 2021 - ExpreS2ion Biotechnologies ApS (“ExpreS2ion”) and its protein production platform ExpreS2™ have contributed to a scientific article published in the journal Med. The article highlights the outcome of the VAC063-study, a Phase I/IIa clinical trial to assess the safety, immunogenicity, and efficacy of the blood-stage Plasmodium falciparum malaria vaccine candidate RH5.1/AS01B

RH5.1/AS01 Malaria Vaccine Clinical Trials

This Phase I/IIa Clinical Trial is to Assess the Safety, Immunogenicity, and Efficacy of the Blood-stage Plasmodium Falciparum Malaria Vaccine Candidate RH5.1/AS01.

This study was completed on June 27, 2019. 

Findings were posted by Med NY on June 11, 2021.

Findings: The RH5.1/AS01B formulation was administered using a range of RH5.1 protein vaccine doses (2, 10, and 50 μg) and was found to be safe and well-tolerated. A regimen using a delayed and fractional third dose, in contrast to three doses given at monthly intervals, led to significantly improved antibody response longevity over ∼2 years of follow-up. Following primary and secondary CHMI of vaccinees with blood-stage P. falciparum, a significant reduction in parasite growth rate was observed, defining a milestone for the blood-stage malaria vaccine field. We show that growth inhibition activity measured in vitro using purified immunoglobulin G (IgG) antibody strongly correlates with in vivo reduction of the parasite growth rate and also identify other antibody feature sets by systems serology, including the plasma anti-RH5 IgA1 response, that are associated with challenge outcome.

Conclusions: Our data provide a new framework to guide rational design and delivery of next-generation vaccines to protect against malaria disease.

Clinical Trials

No clinical trials found