In a 2018 study, serum zinc levels were found to be significantly lower among pneumonia pediatric patients admitted to PICU compared with patients admitted to other wards; there was a statistically significant decrease in zinc level in critically ill children complicated by sepsis, mechanically ventilated and fatal cases [252]. Some studies reported similar duration of hospital stay, time to symptoms resolution, and risk of treatment failure in the intervention and in the control group [254,255,256,258,259,262,264,265], while others described partially positive results. Basnet and colleagues [260] found that zinc recepients recovered slightly faster than controls, although the difference was not statistically significant; Sempertegui et al. [263] evidenced that a higher basal zinc concentration was associated with faster resolution of chest indrawing, although there was no difference in time needed to fully recover nor in the risk of treatment failure; Mahalanbis et al. found a reduced duration of ALRI symptoms in boys, but not in girls [253].