First-in-human trial in Burkinabe adults and children of replication-competent, genetically attenuated PfSPZ-LARC2 Vaccine for malaria

The World Health Organization has called for malaria vaccines with > 90% efficacy against Plasmodium falciparum (Pf) infection.

By Sirima, Richie, Ouedraogo +26Oct 21, 2026

Score█████░░░░░4.8

Key numbers

50,000 times within a hepatocyte
90% efficacy against Plasmodium falciparum
100% protective efficacy at 12

Caveats

Preprint; not yet peer reviewed.

VerdictWorth a reader's time today.

Read the original PDF

Abstract

The World Health Organization has called for malaria vaccines with > 90% efficacy against Plasmodium falciparum (Pf) infection. The live, non-attenuated PfSPZ-CVac (chloroquine) vaccine provides the strongest protection against controlled human malaria infection (CHMI). Its 100% protective efficacy at 12 weeks against genetically distant Pf stems from a highly amplified immune stimulus. After inoculation, each invading sporozoite (SPZ) replicates up to 50,000 times within a hepatocyte. Over six days of development, these parasites express thousands of distinct proteins, presenting a vast and diverse array of antigens to the host immune system. The late liver stage parasites then rupture into the bloodstream, where they are killed by the co-administered drug, chloroquine. To engineer a Pf parasite that develops to the late liver stage like PfSPZ-CVac (chloroquine), but then arrests before transitioning to the blood stage, two genes required for transition from non-pathogenic liver to pathogenic blood stages were identified and deleted, creating late-liver stage arresting, replication-competent (LARC) PfSPZ. In a first-in-human, randomized, double-blind, placebo-controlled clinical trial, we assessed PfSPZ-LARC2 Vaccine in 75 malaria-exposed Burkinabe 1- to 48-year-olds. No vaccine-strain breakthrough blood-stage infections were detected; safety and tolerability profiles were similar in vaccinees and placebo recipients; and the highest immunogenicity was observed in the youngest recipients. Based on these findings, PfSPZ-LARC2 Vaccine has progressed to Phase 2 testing with the goal of rapidly advancing this genetically attenuated whole parasite vaccine to licensure and deployment.

S. B. Sirima, T. L. Richie, A. Ouedraogo, B. I. Soulama, A. R. Zou, I. Nebie, N. KC, N. Camargo, D. Goswami, J. M. T. Kabore, N. Kirakoya, R. K. Mbaiasra, S. Ezinmegnon, E. S. Badoum, S. Y. Ouedraogo, N. B. Henry, J. B. Yaro, T. Mabuka, T. Murshedkar, Y. Abebe, D. Perez, E. R. James, N. Minkah, A. M. Vaughan, M. B. Laurens, B. K. L. Sim, S. H. I. Kappe, A. B. Tiono, S. L. Hoffman

The editor's rubric

Heuristic review

Leverage3 / 5: A method or resource many groups across the field will adopt within a year.; 10% of this desk’s rubric
Magnitude3 / 5: Large gain: roughly 2x, or a clear new state of the art on a hard, unsaturated problem.; 20% of this desk’s rubric
Evidence3 / 5: Solid: multiple benchmarks or cohorts, ablations, fair baselines, released code or data.; 32% of this desk’s rubric
Novelty2 / 5: A new combination of known ideas.; 8% of this desk’s rubric
Trajectory2 / 5: Some room to improve with obvious engineering.; 5% of this desk’s rubric
Stakes3 / 5: Meaningful benefit to many people within a few years.; 25% of this desk’s rubric

Dimension	Level	Weight	What that level means
Leverage	███░░ 3	10%	A method or resource many groups across the field will adopt within a year.
Magnitude	███░░ 3	20%	Large gain: roughly 2x, or a clear new state of the art on a hard, unsaturated problem.
Evidence	███░░ 3	32%	Solid: multiple benchmarks or cohorts, ablations, fair baselines, released code or data.
Novelty	██░░░ 2	8%	A new combination of known ideas.
Trajectory	██░░░ 2	5%	Some room to improve with obvious engineering.
Stakes	███░░ 3	25%	Meaningful benefit to many people within a few years.

Editor’s rationale

Heuristic triage from title and abstract text only, not a reading of the paper. Cues found: method (named contribution); breadth (wide range); gains (x-fold, efficacy); design (randomized, blinded, placebo-controlled); verification (independent replication); stakes (major disease, prevention or cure, genetic disease). Red flags: hype (hype words).

How the score was computed

rank-2026-10-18

Score█████░░░░░4.8

Score = 10 × (80% × adjusted merit / 10 + 10% × attention + 10% × freshness)

Desks place stronger verdicts first, then use this score to order work within the same verdict.

Merit: 5.7 / 10; Weighted rubric, evidence-gated.
Adjusted merit: 4.9 / 10; Shrunk toward the desk prior by editor confidence (50%).
Attention: 0%; Citations, upvotes, points, mentions.
Freshness: 92%; Half-life decay since publication.

Citations0 (reference 20, via semantic-scholar, Oct 22, 2026, 06:17 UTC)

The record

Reviewed by heuristic-v7 on Oct 22, 2026, 06:17 UTC. Paper type: clinical.
Categories: infectious diseases
BRIEF, No.2 in the Medicine edition of October 22, 2026.