Recently Immunized Febrile Infants Have Low Infection Risk

TOPLINE:

Recently immunized febrile infants aged 6-12 weeks exhibited a low risk for invasive bacterial infections (IBIs), with a significantly lower risk for non-IBI within the first 24 hours after immunization versus nonrecently immunized infants.

METHODOLOGY:

• Researchers evaluated 508 infants aged 6-12 weeks who presented with a fever of 38 °C or greater at two US military academic emergency departments (EDs) over a span of 4 years.
• The infants were categorized as “recently immunized” if they had received immunizations within 72 hours before ED presentation and “not recently immunized” if they had not. Among the 508 infants, 114 were immunized recently.
• The primary outcome was the prevalence of a serious bacterial infection (SBI), categorized into IBI and non-IBI on the basis of culture and radiography findings.

TAKEAWAY:

• The prevalence of SBI was 3.5% in the recently immunized febrile infants and 13.7% in not recently immunized febrile infants.
• Among the recently immunized infants, the prevalence of SBI was lower in those immunized within the first 24 hours than those immunized more than 24 hours before ED presentation (2% vs 14.3%, respectively).
• Almost all identified SBI cases were of urinary tract infection (UTI), with the only non-UTI case being pneumonia in an infant who exhibited respiratory symptoms within 24 hours of receiving immunization.

IN PRACTICE:

Physicians should discuss the possibilities of a less invasive approach for evaluating recently immunized febrile infants. The study findings support the general recommendation to obtain a urinalysis for all recently immunized infants over 60 days presenting with fever, including those presenting less than 24 hours post immunization.

SOURCE:

This study, led by Kyla Casey, MD, Department of Emergency Medicine, Naval Medical Center San Diego, was published online in The American Journal of Emergency Medicine.

LIMITATIONS:

The small sample size and retrospective design might have resulted in an overestimation of outcomes like IBIs within 24 hours after immunization. As the study was conducted in a specific clinical setting with febrile infants from military medical centers, the findings may have limited generalizability. Moreover, the inclusion of premature infants without age correction for prematurity could have impacted the prevalence of IBIs. Factors like missing vaccination history, healthcare referral patterns, and immunization practices in the military system may have introduced bias.

DISCLOSURE:

This research did not receive any specific grant from funding agencies in the public, commercial, or not for profit sectors. The authors had no conflicts of interest to disclose.

A version of this article appeared on Medscape.com.