SARS-CoV-2 infection in infants under 1 year of age in Wuhan City, China

Background The clinical characteristics and outcome of COVID-19 in children are different from those in adults. We aimed to describe the characteristics of infants under 1 year of age (excluding newborns) with COVID-19. Methods We retrospectively retrieved data of 36 infants with SARS-CoV-2 infection in Wuhan Children's Hospital from January 26 to March 22, 2020. Clinical features, chest imaging findings, laboratory tests results, treatments and clinical outcomes were analyzed. Results The mean age of the infected infants was 6.43 months, with a range of 2-12 months. 61.11% of the patients were males and 38.89% females. 86.11% of the infants were infected due to family clustering. Cough (77.78%) and fever (47.22%) were the most common clinical manifestations. Chest CT scan revealed 61.11% bilateral pneumonia and 36.11% unilateral pneumonia. 47.22% of the infants developed complications. Increased leucocytes, neutrophils, lymphocytes, and thrombocytes were observed in 11.11, 8.33, 36.11 and 44.44% of infants, respectively. Decreased leucocytes, neutrophils, thrombocyte and hemoglobin were observed in 8.33, 19.44, 2.78 and 36.11% of infants, respectively. Increased C-reactive protein, procalcitonin, lactate dehydrogenase, alanine aminotransferase, creatine kinase and D-dimer were observed in 19.44, 67.74, 47.22, 19.44, 22.22 and 20.69% of infants, respectively. Only one infant had a high level of creatinine. Co-infections with other respiratory pathogens were observed in 62.86% of infants. CD3 (20.69%), CD4 (68.97%), CD19 (31.03%) and Th/Ts (44.83%) were elevated; CD8 (6.9%) and CD16+CD56 (48.28%) was reduced. IL-4 (7.69%), IL-6 (19.23%), IL-10 (50%), TNF-alpha (11.54%) and IFN-gamma (19.23%) were elevated. Up to March 22, 97.22% of infants recovered, while a critical ill infant died. When the infant's condition deteriorates rapidly, lymphocytopenia was discovered. Meanwhile, C-reactive protein, D-dimer, alanine aminotransferase, creatine kinase, creatinine, IL-6 and IL-10 increased significantly. Conclusions In the cohort, we discovered that lymphocytosis, elevated CD4 and IL-10, and co-infections were common in infants with COVID-19, which were different from adults with COVID-19. Most infants with COVID-19 have mild clinical symptoms and good prognosis.