Severe and invasive bacterial infections in infants aged less than 90 days with and without SARS-CoV-2 infection.

Background: Fever in children represents one of the most common causes of medical evaluation. Infants younger than 90 days of age are at higher risk of severe and invasive bacterial infections (SBI and IBI). However, clinical signs and symptoms of viral and bacterial infections in young infants are frequently similar, and several studies have shown that the risk of SBIs remains non-negligible even in the presence of a positive point-of-care viral test. Our study aims to evaluate whether the proportion of SBIs and IBIs in febrile infants younger than 90 days during the COVID-19 pandemic was higher than that in the pre-pandemic period, and to describe the proportion of SBIs and IBIs in infants with and without SARS-CoV-2 infection.

Methods: This was a retrospective single-center cohort study conducted at the Children's Hospital of the University of Padua in Italy, involving febrile young infants evaluated in the Pediatric Emergency Department (PED) and admitted to Pediatric Acute Care Unit (PACU) between March 2017 to December 2022. Infants admitted before the COVID-19 pandemic were compared to infants admitted during the pandemic period and SARS-CoV-2 positive patients to the negative ones.

Results: 442 febrile infants younger than 90 days were evaluated in Padua PED and admitted to the wards. The proportion of SBIs and IBIS did not significantly change over the study periods, ranging between 10.8% and 32.6% (p = 0.117) and between 0% and 7.6%, respectively (p = 0.367). The proportion of infants with a diagnosis of SBIs and IBIs was higher in the SARS-CoV-2 negative group (30.3% and 8.2%, respectively) compared to the positive group (8.5% and 2.8%, respectively) (p < 0.0001). The most common diagnosis in both groups was UTI, mainly caused by E. coli. A similar proportion of blood and urine cultures were performed, whereas lumbar puncture was more frequently performed in SARS-CoV-2 negative infants (40.2% vs 16.9%, p = 0.001).

Conclusions: Although the risk of concomitant serious bacterial infection with SARS-CoV-2 is low, it remains non-negligible. Therefore, even in SARS-CoV-2-positive febrile infants, we suggest that the approach to screening for SBIs remains cautious.