Oral Presentation First Malaria World Congress 2018

Implications for population immunity & the hidden benefits of malaria elimination   (#12)

Kevin Marsh 1
  1. University of Oxford, OX1 2JD, United Kingdom

As countries  move to malaria elimination  there are profound changes at the population level with both positive and negative implications. First, the gains  of elimination are often  seen  primarily in terms of reductions in malarial disease although there has long been the suggestion that removal of vaguely defined  malaria induced ‘immune suppression’ may  confer other  health benefits. A number of recent findings strongly support this; first the observation that sickle cell trait, long known to protect against malaria, confers protection against bacteraemia  allowed   a Mendelian   randomisation  approach to demonstrate that malaria directly leads to  a large burden of severe bacterial  disease which is reduced as malaria transmission reduces.  This is supported by  major reductions  in childhood  mortality  associated with  time limited antimalarial interventions. On the less positive side, reductions in malaria transmission lead to reductions  in antimalarial immunity rendering populations susceptible to  more severe disease should there be any rebound in transmission. The dynamics  of this are complex and involve two different  phenomena: the gradual accumulation  of a birth cohort no longer exposed to malaria and the possible waning of established immunity in older members of the population.