NIH-funded study reveals why malaria vaccine only partially protected children, infants

Public Release: 22-Oct-2015


NIH/National Institute of Allergy and Infectious Diseases

Using new, highly sensitive genomic sequencing technology, an international team of researchers has found new biological evidence to help explain why the malaria vaccine candidate RTS,S/AS01 (called RTS,S) provided only moderate protection among vaccinated children during clinical testing. The researchers, funded in part by the National Institute of Allergy and Infectious Diseases at the National Institutes of Health, found that genetic variability in the surface protein targeted by the RTS,S vaccine likely played a significant role. The findings are published online today in the New England Journal of Medicine.

The RTS,S vaccine was designed to target the circumsporozoite (CS) protein found on the surface of malaria-causing Plasmodium parasites. However, while the CS protein is genetically diverse, meaning that it has different variants, the RTS,S vaccine incorporates only one variant. In an evaluation of blood samples from nearly 5,000 of the infants and children who participated in Phase 3 clinical testing of the vaccine, the researchers found that the RTS,S vaccine was most effective at preventing malaria in children ages 5 to 17 months infected with parasites with the same protein variant as the RTS,S vaccine, while a mismatch corresponded with a lesser degree of protection. This differential effect was not seen in blood samples from vaccinated infants ages 6 to 12 weeks.

Previous studies that have looked at the genetic variations in the CS protein did not suggest that these variations may limit or restrict vaccine protection. This new study included a larger sample size and used advanced, more sensitive genomic sequencing technology than previously available. The findings will inform future malaria vaccine development, and the genomics approach used could be applied to other infectious diseases with changing vaccine targets, according to the authors.


This research was conducted with NIAID support provided under contract number HHSN2727200900018C.


Daniel E. Neafsey et al. Genetic Diversity and Protective Efficacy of the RTS,S/AS01 Malaria Vaccine. New England Journal of Medicine DOI: 10.1056/NEJMoa1505819 (2015).


NIAID Director Anthony S. Fauci, M.D., and Lee Hall, M.D., Ph.D., chief of NIAID’s Parasitology and International Programs Branch, are available to comment on this study.


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NIAID conducts and supports research–at NIH, throughout the United States, and worldwide–to study the causes of infectious and immune-mediated diseases, and to develop better means of preventing, diagnosing and treating these illnesses. News releases, fact sheets and other NIAID-related materials are available on the NIAID website.

About the National Institutes of Health (NIH): NIH, the nation’s medical research agency, includes 27 Institutes and Centers and is a component of the U.S. Department of Health and Human Services. NIH is the primary federal agency conducting and supporting basic, clinical, and translational medical research, and is investigating the causes, treatments, and cures for both common and rare diseases. For more information about NIH and its programs, visit

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Categories: . Vaccine failure

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