71 - Serious bacterial infection in recently immunized young infants with fever without a source.

Poster Number: 71
Publication Number: 71.105

Borja Gomez, Pediatric Emergency Department. Cruces University Hospital, Barakaldo, Pais Vasco, Spain; Eider Lopez, Cruces University hospital, bilbao, Pais Vasco, Spain; Ana María Barreiro Parrado, Cruces University Hospital, Bilbao, Pais Vasco, Spain; Amaia Fernandez-Uria, Cruces University Hospital, Bilbo, Pais Vasco, Spain; Ainara Lejarzegi, Osakidetza, Zalla, Pais Vasco, Spain; Javier Benito, Cruces University Hospital, Bilbao, Pais Vasco, Spain; Santiago Mintegi, Hospital Universitario Cruces, Bilbao, Pais Vasco, Spain

Background: The American Academy of Pediatrics recently published guidelines addressing the evaluation and management of infants 8 to 60 days of age with fever≤38.0ºC. Evidence is lacking regarding the best approach to young febrile infants who have received immunizations within the previous 48 hours. For this reason, these infants were excluded from these guidelines.

Objective: To compare the prevalence of invasive bacterial infection (IBI) and urinary tract infection (UTI) in infants 42 to 90 days of age with fever without a source (FWS) who have received immunizations in the preceding 48 hours and those who have not.

Design/Methods: We carried out a secondary analysis of a prospective registry that includes all the infants ≤90 days of age with FWS attended in a pediatric ED. We analyzed those 42 to 90 days of age infants attended over an 11-year period (2010–2021). Preterm infants ( < 37 weeks’ gestation) were excluded. We classified the infants either as having received immunizations (RI group) within the 48 hours preceding the ED visit or as not having received immunizations (non-RI group) during that period. We compared the prevalence of IBI (isolation of a bacterial pathogen in blood or cerebrospinal fluid) and UTI (urine culture with growth of ≥10 000 CFU/mL in combination with leukocyturia) in both groups.

Results: We registered 1490 episodes corresponding to infants 42 to 90 days of age born at term with FWS. Information about recent immunization was available in 1448 (97.1%): 174 (12.0%) included in the RI group and 1274 (88.0%) in the non-RI group. Among the infants included in the RI-group, 77.6% of them had received the immunization in the same day the fever began.
Overall, 272 (18.7%) were diagnosed with an UTI and 18 (1.2%) with an IBI (10 UTIs with associated bacteremia, 7 occult bacteremias and 1 sepsis). The prevalence of UTI was significantly lower in the RI group [6.9% vs 20.4% in the non-RI group, p < 0.01; Odds Ratio: 0.28 (95% CI: 0.15-0.52)]. None of the recently immunized infants were diagnosed with an IBI [vs 18 of the non-RI group (1.4%), p=0.15]Conclusion(s): Although the prevalence of UTI in infants 42 to 90 days of age with FWS who have received immunizations within the previous 48 hours is lower, recommending screening for UTI seems appropriate. Prevalence of IBI was also lower among infants with a recent immunization. If further studies confirm this finding, the recommendation of performing blood tests systematically in these infants should be reconsidered.