Sequential acquisition of T cells and antibodies to Salmonella Typhimurium (STm) in children. Age distribution of STm bloodstream infection in children <5 years old at Queen Elizabeth Central Hospital (Blantyre, Malawi; 2006–2011) was superimposed with kinetics of STm-specific CD4⁺ T-cell immune responses and STm-specific serum bactericidal activity (y-axis was inverted) in children aged 0–60 months. Abbreviations: CFU, colony-forming units; SBA, serum bactericidal activity.