The Prevalence of Bacterial Infection in Recently Vaccinated Febrile Infants

Background and aims: Evidence is lacking regarding the best approach to evaluating recently vaccinated infants younger than 3 months who present to the emergency department (ED) with fever. There have not been any recent published studies assessing the prevalence of bacterial infections in this population. The aim of the present study is to investigate the prevalence of bacterial infections in young infants presenting with fever within 72 hours after vaccination.

Methods: We reviewed the electronic medical records of infants aged between 6-12 weeks who presented with a fever >38C to paediatric ED, Tallaght University Hospital, Dublin, from January 2018 to December 2018. Febrile infants who recently vaccinated within 72 hours prior to ED presentation were compared with those who did not recently vaccinated. Bacterial infection were diagnosed based on culture results (urine or blood or CSF).

Results: A total of 70 infants (age: 8.8±1.9 weeks, male: 40(57.1%)) were enrolled in this study. Among 70 infants, 19 (27.1%) had recently vaccinated, of whom 11(57.9%) presented to ED within 24 hours of vaccination, 7 (36.8%) presented 24-48 hours after vaccination and 1(5.3%) presented 48-72 hours after vaccination. The prevalence of bacterial infection in non-recently vaccinated infants was 17.6% compared to 10.5% in recently vaccinated infants. Interestingly, all vaccinated infants who had bacterial infection, were presented to ED with fever within 24 hours of vaccination and all bacterial infections in this group were urinary tract infection (UTI).

Conclusion: Fever should not be attributed only to the vaccinations in young Infants who present to paediatric ED with fever after recent vaccination. All febrile recently vaccinated infants should be carefully evaluated and at least urine testing should be done regardless of the time of vaccination after the presentation.