Assessing Vaccine Effectiveness of R21/Matrix-M Across Malaria Transmission Settings (AVERT)

Inclusion Criteria: * Residence in an area where R21/Matrix-M is implemented and within the catchment area of a selected study facility. * Younger than 5 years and eligibleto receive R21/Matrix-M under the national vaccination schedule at rollout. * Meets the country definition of suspected malaria, generally axillary temperature of at least 37.5 degrees Celsius or a history of fever within the previous 24 hours, and is undergoing malaria testing. * Written informed consent provided by an adult caregiver aged 18 years or older. Exclusion Criteria: * Caregiver is unable or unwilling to provide informed consent. * Severe non-malaria illness at presentation that would interfere with study participation. * Repeat presentation within the protocol-defined exclusion window after a previous enrollment: within 14 days after a microscopy-positive visit; or more than 7 but fewer than 14 days after a microscopy-negative visit. A microscopy-negative visit followed by a positive diagnosis within 7 days will be reclassified as positive rather than treated as a new enrollment. * Documented receipt of any RTS,S malaria vaccine dose.