IL6 and malaria: No differences in IL-6 levels between patients with severe malaria and non-severe malaria among the studies that enrolled only children (P = 0.147, WMD = 98.5 pg/mL, 95% CI =  − 34.46 −231.47 pg/mL, I2 = 100%, eight studies) and only adults (P = 0.155, WMD = 67.64 pg/mL, 95% CI =  − 25.56 −160.84 pg/mL, I2 = 98.4%, three studies; Fig. 5) were observed.