Longitudinal Dynamics of Anti-Plasmodium Immunity in Relation to Transmission Intensity in a Nigerian Cohort: A Five-Year Study

The acquisition kinetics and durability of naturally acquired anti-Plasmodium immunity are critically shaped by cumulative transmission intensity, yet longitudinal cohort data from Nigeria's highly heterogeneous transmission settings remain limited. This doctoral study characterised longitudinal anti-Plasmodium immunity dynamics across five years in two cohorts: one from a high-transmission riverine community in Anambra State and one from a low-transmission urban community in Abuja, North Central Nigeria. A total of 320 children aged 1 to 10 years at baseline were enrolled per cohort and followed with six-monthly clinical assessments and blood sampling. Antibody titres to AMA1, MSP1-19, MSP2, and GLURP antigens were measured by ELISA at each timepoint. Malaria clinical episodes were recorded prospectively. Mixed-effects regression models assessed antibody-acquisition and decay kinetics. High-transmission cohort children acquired anti-AMA1 IgG titres reaching protective thresholds (defined by literature correlates) approximately 24 months earlier than low-transmission cohort peers. Anti-MSP1-19 antibodies showed the highest durability with half-life greater than 36 months in high-transmission children. Protection against clinical malaria was significantly associated with anti-AMA1 and anti-MSP2 antibody levels in both cohorts (p less than 0.01). The study provides the most comprehensive longitudinal immunity acquisition dataset from Nigeria to date and informs age-targeted vaccine deployment strategies. Keywords: naturally acquired immunity, Plasmodium falciparum, longitudinal cohort, transmission intensity, Nigeria.