Serious Bacterial Infection Risk in Febrile Infants Aged ≤90 Days With COVID-19

Background This retrospective cohort study compared the risk of serious bacterial infection (SBI) in febrile infants aged ≤90 days with and without COVID-19. While some studies have suggested that COVID-19-positive febrile infants may have a lower risk of SBI, this remains unclear, particularly in Japan. We investigated the incidence of SBI and clinical characteristics in COVID-19-positive versus COVID-19-negative febrile infants. Methods Febrile infants aged ≤90 days who visited the emergency department of the children's hospital in Japan between April 2021 and November 2022 were enrolled. The subjects were divided into a COVID-19 group, defined as subjects with positive polymerase chain reaction (PCR) findings for SARS-CoV-2 or those with close contact with a SARS-CoV-2 PCR-positive family member. SBI was defined as urinary tract infection (UTI), bacterial pneumonia, bacteremia, or bacterial meningitis. Results In total, 396 patients were included; of these, 125 patients were in the COVID-19 group. SBI was diagnosed in 7/125 patients (5.6%) of this group vs. 45/271 patients (16.6%) of the non-COVID-19 group (p<0.05). All cases of SBI diagnosed in the former were of UTI. No notable differences in respiratory or gastrointestinal symptoms were observed between patients with and without SBI. Conclusion The present study demonstrated that the SBI rate was significantly lower in the COVID-19 group than in the non-COVID-19 group. However, the complication rate of SBI, especially UTI, was not negligible, suggesting that at least urinalysis should be performed for target patients. Our study provided more evidence to support the published data pertaining to the risk of SBI in febrile infants with COVID-19.