April 25, 2021
- Malaria is a serious and sometimes deadly disease caused by the parasite Plasmodium falciparum.
- Malaria is usually transmitted by infected Anopheles mosquitoes.
- The progression in controlling the disease stalled and the need for an effective and deployable vaccine has been emphasized.
- RTS,S/AS01 is the world’s first malaria vaccine shown to provide protection against malaria in young children.
- RTS,S/AS01 is the most effective malaria vaccine up to date and showed 55.8% efficacy over 12 months in African children.
- Researchers conducted a double-blind study of a low-dose circumsporozoite protein-based vaccine called R21.
- Circumsporozoite protein is a secreted protein of the sporozoite stage of the malaria parasite.
- Two different doses of adjuvant, Matrix-M™, were added to the R21 vaccine.
- An adjuvant is a substance that increases the effectiveness of a vaccine.
- The group composed of 5 to 17 month-old children in Nanoro, Burkina Faso.
- Prior to the malaria season, vaccinations were administered every 4 weeks.
- Three vaccinations were administered with a fourth dose one year later.
- Over one year, the safety, immunogenicity, and efficacy were evaluated.
- 450 children were randomized to receive the R21-Matrix-M™ vaccine or a control rabies vaccine.
- R21-Matrix-M™ had a 43 favorable safety profile.
- After 6 months, 29.5% who received R21-Matrix-M™ with low dose adjuvant developed malaria.
- 26% who received R21-Matrix-M™ with high-dose adjuvant developed malaria.
- 71.4% who received the control rabies vaccine developed malaria.
- On average, 72.25% who received R21-Matrix-M™ did not develop clinical malaria.
- Vaccine efficacy was 74% and 77% in the low and high dose adjuvant groups respectively.
- After one year, vaccine efficacy remained at 77% in the high-dose adjuvant group.
- After 28 days from the third vaccination, the individuals showed a high concentration of malaria-specific antibodies.
- Malaria-specific antibodies were doubled in a higher adjuvant dose.
- Antibodies diminished however, they were boosted to levels similar to peak concentrations after the primary series of vaccinations following the fourth dose administered one year later.
 Porter, Michael; Jennifer Nicki; Christopher Pool (June 2013). “Transgenic Parasites Stably Expressing Full-Length Plasmodium falciparum Circumsporozoite Protein as a Model for Vaccine Down-Selection in Mice Using Sterile Protection as an Endpoint”. Clinical and Vaccine Immunology. 20 (6): 803–810. doi:10.1128/cvi.00066-13. PMC 3675977. PMID 23536694