Objective We aimed to evaluate the association of height of fever with invasive bacterial infection (IBI) among febrile infants <=60 days of age.

Methods In a secondary analysis of a multicentre case–control study of non-ill-appearing febrile infants <=60 days of age, we compared the maximum temperature (at home or in the emergency department) for infants with and without IBI. We then computed interval likelihood ratios (iLRs) for the diagnosis of IBI at each half-degree Celsius interval.

Results The median temperature was higher for infants with IBI (38.8°C; IQR 38.4–39.2) compared with those without IBI (38.4°C; IQR 38.2–38.9) (p<0.001). Temperatures 39°C–39.4°C and 39.5°C–39.9°C were associated with a higher likelihood of IBI (iLR 2.49 and 3.40, respectively), although 30.4% of febrile infants with IBI had maximum temperatures <38.5°C.

Conclusions Although IBI is more likely with higher temperatures, height of fever alone should not be used for risk stratification of febrile infants.