Is It Just The Vaccine? Post-Vaccination Fever in Infants

May 15, 2024

Written by Millie Cossé

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Serious bacterial infections were significantly less common in this study of recently immunized infants 6-12 weeks presenting to the emergency department with a fever.

It’s probably just the vaccine, right?
Fever is an anticipated reaction to childhood immunization, and the evaluation of the recently immunized febrile infant presents a diagnostic challenge in the emergency department. This retrospective chart review evaluated the prevalence of serious bacterial infections in infants aged 6-12 weeks who presented to the emergency department with a fever (≥38°C). Patients were divided based on immunization status: Infants who had received immunizations in the preceding 72 hours were considered recently immunized (RI), and the remainder were considered non recently immunized (NRI). The prevalence of serious bacterial infection in NRI infants was 13.7% (95%CI 10.6-17.6) compared to 3.5% (95%CI 1.1-9.3) in RI infants. Authors identified no cases of bacteremia or meningitis in the RI group, and all but one case of serious bacterial infection was due to urinary tract infection.

How will this change my practice?
Currently, children who have been immunized in the last 48 hours are excluded from the American Academy of Pediatrics febrile infant guideline. In the well-appearing infant who has received vaccines within the last 48 hours, we have a great opportunity to use shared decision making with parents. I’ll be advocating for at least a urinalysis with culture in these patients.

Source
Serious bacterial infection risk in recently immunized febrile infants in the emergency department. Am J Emerg Med. 2024 Mar 24;80:138-142. doi: 10.1016/j.ajem.2024.03.025. Epub ahead of print. PMID: 38583343.