Children younger than 36 months with fever without a source (FWS) are at risk of serious bacterial infections (SBI). The risk of occult bacteremia (OB) has been greatly reduced in vaccinated children. The aim of this study is to describe the epidemiology of SBI in children with FWS in our setting and to evaluate the performance of our management algorithm.

We designed a prospective cohort study. We included children aged 0–36 months presenting with FWS in our emergency unit. Demographic and clinical characteristics, investigations, and management procedures were recorded at the time of inclusion. Information on clinical evolution, final diagnosis, and immunization history were obtained after 10 days. Potential predictors of SBI were compared between patients with and without SBI.

Between October 2015 and September 2017, 173 children were recruited, with a median age of 4.4 months (2.1–1). Of these children, 166 (96%) were up to date with their vaccinations. A total of 47 children (27%) had a final diagnosis of SBI, which were all urinary tract infections (UTI). Presence of chills (odds ratio [OR] 5.6, 95% confidence interval [CI] 1.3–24.3), fever for>2 days (OR 29.1, 95% CI 3.5–243.5), and age<9 months (OR: 45.3, 95% CI: 4.9–415.7) were statistically significant predictors of UTI in a multivariate logistic regression. The sensitivity and specificity of our management algorithm were 100% (95% CI: 92.4–100%) and 21.4% (14.6–29.6%), respectively.

In the setting of high vaccination coverage, we only identified SBI related to UTIs. We could not identify any OB. Our management algorithm was able to identify all SBI, but specificity was low. Refined criteria for screening of UTI could slightly increase this.