Several studies have demonstrated that antibiotic exposure can safely be decreased by PCT-guided antibiotic therapy, notably in respiratory infections and febrile infants, without affecting clinical outcomes [23,24]. The largest paediatric data set to date, an individual-patient meta-analysis of 2,024 children [12], confirmed that PCT-guided therapy significantly reduced antibiotic duration without compromising safety. Here, CALCA is linked to respiratory tract infectious disorder.