IL-6 has been previously described as a marker of different types of SBI (alone or in combination with other biomarkers) [23, 24] such as early-onset neonatal sepsis [25, 26], sepsis and septic shock [21, 23, 27] bacteremia in patients with febrile neutropenia [28, 29] or pneumococcal pneumonia [30–33]. Here, IL6 is linked to pneumococcal pneumonia.