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The endemic dilemma: why whole sporozoite malaria vaccine efficacy falls in the field
Journal article   Open access   Peer reviewed

The endemic dilemma: why whole sporozoite malaria vaccine efficacy falls in the field

Mariah Hassert and John T. Harty
Trends in parasitology, Vol.42(2), pp.105-114
02/2026
DOI: 10.1016/j.pt.2025.12.003
PMCID: PMC12854258
PMID: 41565496
url
https://doi.org/10.1016/j.pt.2025.12.003View
Published (Version of record) Open Access

Abstract

Whole sporozoite vaccines (WSVs) induce near complete sterilizing immunity in homologous CHMI settings, but efficacy drops in malaria endemic regions for unclear reasons.The ‘antigen mismatch’ hypothesis posits that the limited breadth of genetic diversity in vaccine strains does not capture the parasite genetic diversity in the field, contributing to reduced durability of protection.The ‘host context’ hypothesis posits that variability in vaccine efficacy arises from differences in host genetics, infection history, microbiome, and nutritional status.Both hypotheses should be considered in the design of future malaria vaccines. Whole sporozoite vaccines (WSVs) are the most effective malaria vaccines developed to date. However, their durable efficacy declines sharply when moving from homologous CHMI studies to field trials in endemic regions. We argue this reduced efficacy reflects the complex context of vaccine deployment rather than a single cause. The antigen mismatch hypothesis postulates that limited genetic diversity in current vaccines fails to capture the diversity of field parasites, reducing immune recognition. The host-context hypothesis describes how genetics, infection history, microbiome, and nutrition influence vaccine outcomes. We propose that the future of malaria vaccines will depend on integrating parasite genomics, systems immunology, and the development of animal models which more accurately depict the context of individuals living in malaria endemic regions. Whole sporozoite vaccines (WSVs) are the most effective malaria vaccines developed to date. However, their durable efficacy declines sharply when moving from homologous CHMI studies to field trials in endemic regions. We argue this reduced efficacy reflects the complex context of vaccine deployment rather than a single cause. The antigen mismatch hypothesis postulates that limited genetic diversity in current vaccines fails to capture the diversity of field parasites, reducing immune recognition. The host-context hypothesis describes how genetics, infection history, microbiome, and nutrition influence vaccine outcomes. We propose that the future of malaria vaccines will depend on integrating parasite genomics, systems immunology, and the development of animal models which more accurately depict the context of individuals living in malaria endemic regions.
 liver stage Plasmodium infection Plasmodium whole sporozoite vaccines

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