Immunity to P. vivax malaria protozoa mapped to guide future vaccine design 

Study co-led by WEHI and Burnet Institute identifies functional antibody responses that cut Plasmodium vivax malaria risk by more than 75%

Research co-led by a team from the Walter and Eliza Hall Institute (WEHI) of Medical Research and Burnet Institute, both in Melbourne, Australia, has clarified how the human immune system mounts protection against Plasmodium vivax (P. vivax), the most geographically widespread cause of malaria. The findings have provided detailed evidence of what protective immunity looks like in this infection and have identified specific parasite targets and antibody functions that could underpin the first effective vaccine against this species.

Global malaria research has long concentrated on Plasmodium falciparum, which causes the numbers of deaths, particularly in sub-Saharan Africa. As a consequence, major gaps have persisted in understanding immunity to P. vivax, which predominates across Asia and the Pacific and places millions at risk of recurrent disease.

P. vivax possesses a dormant liver stage – known as a hypnozoite – which can reactivate weeks or months after initial infection and trigger relapse.

“Unlike P. falciparum, P. vivax has unique biological features including a dormant liver stage that causes relapses, making it more difficult to eliminate,” said Dr Rhea Longley, the laboratory head at the WEHI.

“Strategies that work for one species do not translate to the other,” she said.

Despite decades of progress in malaria control, recently developmental momentum has faltered. Two vaccines have entered deployment in parts of Africa targeting P. falciparum  but in regions where P. vivax dominates, populations remain without vaccine-based defence.

“While two malaria vaccines have been rolled out in parts of Africa, [they] both target Plasmodium falciparum and offer no protection against P. vivax, which dominates in Asia and the Pacific,” said Dr Herber Opi, senior research fellow at the Burnet Institute.

A central obstacle in vaccine development has been uncertainty over the precise immune mechanisms that confer protection. The mere presence of antibodies in the bloodstream has not proved sufficient to predict resistance to infection. The present study addressed this problem through detailed immunological analysis of blood samples drawn from children in Papua New Guinea, where P. vivax transmission has remained intense and where repeated exposure provides an opportunity to observe naturally acquired immunity.

Researchers examined how antibodies recognised parasite proteins and how effectively they engaged other components of the immune system. The data demonstrated that protection did not depend simply on antibody quantity. Instead, outcome correlated with functional quality with antibodies recruiting immune cellsaactivating immune pathways, and proving to be far more protective than those that bound parasite proteins without triggering downstream responses.

The team identified particular combinations of parasite proteins that, when targeted simultaneously, elicited markedly stronger immune activation. Children whose immune responses focused on this optimal set of proteins exhibited substantially reduced malaria risk. Targeting the correct combination reduced the likelihood of disease by more than 75%, a level of protection that offers a tangible benchmark for vaccine design.

“These exciting findings open novel avenues to develop P. vivax vaccines to combat the malaria burden globally and support a path to elimination,” said Professor James Beeson, head of malaria immunity and vaccines at the Burnet Institute. He emphasised that the results provide critical evidence to guide antigen selection and formulation strategies.

The work reinforced a broader immunological principle whereby functional antibody responses – rather than sheer concentration – determine clinical protection. Vaccine platforms that aim to induce antibodies must therefore prioritise quality, specificity and the ability to orchestrate a coordinated immune response.

Although mortality from malaria has declined markedly since the early 2000s, progress has plateaued in several regions. For communities across Asia and the Pacific, where P. vivax dominates and disease relapse is commonplace, the absence of a targeted vaccine has represented a conspicuous gap in global public health.

For further reading please visit: 10.1016/j.immuni.2026.02.003