Impact of declining transmission on immunity and risk of malaria rebound

Many trials of interventions to control and prevent malaria have reported rebounds in transmission following an initial period of reduced malaria incidence and mortality. Rebounds malaria have been attributed to a perceived loss of naturally acquired immunity during the period of reduced exposure. However, at present, there is no quantifiable data from studies assessing both the impact of mass drug administration and its effect on naturally acquired antimalarial immunity.

Objective

To achieve the goal of complete elimination of malaria from the Greater Mekong Subregion of Southeast Asia by the year 2030, the World 

Health Organisation now supports mass drug administration in selected high risk populations. Mass drug administration could be particularly effective in this region to eliminate asymptomatic reservoirs of Plasmodium spp. infection.

However there is hesitancy to adopt widescale use of mass drug administration to eliminate malaria over fears of drug resistance selection and its impact on population level antimalarial immunity. Although increases in malaria-associated morbidity following large-scale elimination campaigns have been attributed to a loss of population level antimalarial immunity, and therefore susceptibility to clinical illness, there is little quantifiable evidence of this loss of immunity.

Timeline

2015–2025.

Approach

Utilising data from malaria intervention trials in the Greater Mekong Subregion, we seek to quantify the impact of malaria control measures including the potential elimination on malaria immunity within communities and how this affects the long-term transmission of malaria and the risk of clinical or subclinical infection rebound. Additionally, we seek to understand the association between subclinical infection and the maintenance of antimalarial immunity in this population.

Community impact

This study will quantify the impact of Mass Drug Administration on antimalarial immunity and provide time frames to identify populations at risk of malaria rebound and establishment of submicroscopic infectious reservoirs of parasites. Findings are essential for guiding policy recommendations, the allocation of resources for the prevention of malaria rebound, and achieving malaria elimination in the Greater Mekong Subregion.