Febrile infants under 3 months of age represent a high risk group for serious bacterial infection (SBI) with approximately 10-20% having bacteremia, meningitis or urinary tract infection. The assessment of febrile infants is challenging, and current National Institute for Health and Care Excellence (NICE) guidance advocates a cautious approach with the majority of infantsrequiring a septic screen, parenteral broad-spectrum antibiotics, and admission to hospital. Internationally there is significant variation in the approach to febrile infants with European and USA guidance advocating a tailored approach based on clinical features and biomarker testing. None of the available clinical decision (CDAs) have been validated in a UK and Irish cohort.