The diversity in the clinical features of children hospitalized with COVID-19 during the nonvariant, Alpha (B.1.1.7), Delta (B.1.617.2), and Omicron (B.1.1.529) variant periods of SARS CoV-2: Caution for neurological symptoms in Omicron variant.

Since the COVID-19 pandemic began, various severe acute respiratory syndrome coronavirus 2 variants have been identified with different characteristics than the nonvariant strain. We retrospectively evaluated the demographic and clinical differences in the cohort of hospitalized COVID-19 children (1 month-18 years old) between March 11, 2020, and September 31, 2022, by the time the variants identified in our country predominate. Bonferroni post hoc analysis was performed to compare the differences between the periods. Of the 283 children in this study, 142 (50.2%) were females. The median age was 36 (interquartile range [IQR]: 7-132) months. Sixty-three (22.2%) patients were hospitalized in the nonvariant period, 24 (8.5%) in the Alpha period, 93 (32.9%) in the Delta period, and 103 (36.4%) in the Omicron period. Fever was the most common symptom in all groups, with no statistically significant differences (p = 0.25). In the Omicron period, respiratory and gastrointestinal symptoms decreased, and neurological symptoms increased significantly compared to other periods: [respiratory symptoms; nonvariant (65.1%) vs. Omicron (41.7%), (p = 0.024)], [gastrointestinal symptoms; Delta (41.9%) vs. Omicron (22.3%), (p = 0.018), [neurological symptoms; Delta (14.5%) vs. Omicron (31.1%), (p = 0.03]. Altered mental status and seizures were more common during the Omicron period compared to the pre-Omicron (nonvariant, Alpha, and Delta) period (p = 0.017 and p = 0.005, respectively). Although the main symptoms in children with COVID-19 were fever and respiratory symptoms, an increase in severe neurological manifestations was seen throughout the Omicron variant period.