Table 1 Study Parameters and Operational Definitions

Anemia

The decrease in whole-blood hemoglobin concentration of more than 2 standard deviations below the mean of age- and sex-matched reference range [19].

VOC

Any painful episode requiring the intake of an analgesic (e.g., paracetamol, ibuprofen, or tramadol) or leading to a medical consultation in a healthcare structure.

Infectious episode

Any noted increase in the body temperature beyond 38.5 °C needed to be managed in a healthcare facility.

Red blood cell transfusion

Any administration of labile blood products (in particular, packed red blood cells or whole blood) that occurred in a healthcare facility.

Acute chest syndrome

Presence of fever, cough, chest pain, difficulty breathing ± performance of chest X-ray.

Jaundice

A clinical observation, i.e., the presence of yellow coloration of the bulbar conjunctiva.

Hospitalization

Admission to hospital for treatment lasting at least 24 h.

Adherence to care

Assessed as excellent, fair, or poor depending on the clinical follow-up as observed.

Large city

A city with an urban landscape and an international airport that is directly connected to foreign countries.

Remote city

Urban-rural town in the country with no direct contact with foreign countries.