Clinical Characteristics of Hospitalized Children With Coronavirus Disease 2019 After the Spread of the BA.5 Omicron Variants in Japan

Jun Tachikawa; Yuta Aizawa; Tatsuki Ikuse; Takayuki Yamanaka; Satoshi Hasegawa; Akihiko Saitoh

doi:10.1097/INF.0000000000004729

Clinical Characteristics of Hospitalized Children With Coronavirus Disease 2019 After the Spread of the BA.5 Omicron Variants in Japan

Pediatr Infect Dis J. 2025 Jan 21. doi: 10.1097/INF.0000000000004729. Online ahead of print.

Authors

Jun Tachikawa¹, Yuta Aizawa¹, Tatsuki Ikuse¹, Takayuki Yamanaka², Satoshi Hasegawa³, Akihiko Saitoh¹

Affiliations

¹ From the Department of Pediatrics, Niigata University, Graduate School of Medical and Dental Sciences, Niigata, Japan.
² Department of Pediatrics, Niigata City General Hospital, Niigata, Japan.
³ Department of Patient Coordinate Center, Niigata Prefectural Office, Niigata, Japan.

PMID: 39841934
DOI: 10.1097/INF.0000000000004729

Abstract

Background: The spread of the BA.5 Omicron variant of severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) has increased the number of hospitalized children. However, the impact of the spread of new omicron subvariants in children remains poorly described.

Methods: This prospective observational study evaluated the clinical characteristics of children hospitalized with coronavirus disease 2019 (COVID-19) in 13 hospitals in Niigata, Japan, during September 2022-February 2024. The data were divided and compared across 3 periods based on the dominant subvariants: BA.5/BF.5/BF.7 period (September 2022-April 2023), XBB/EG.5 period (May-December 2023) and BA.2.86/JN.1 periods (January-February 2024). In addition, the COVID-19 vaccination rates in hospitalized patients were compared with those in the general population.

Results: In total, 298 children with COVID-19 were hospitalized during the study period. The patients' median ages were 4.7 years during the BA.5/BF.5/BF.7 period, 1.2 years during the XBB/EG.5 period and 2.4 years during the BA.2.86/JN.1 period. The peak monthly number of admissions decreased over time, with 44, 32, 19 cases/mo during the BA.5/BF.5/BF.7 period, the XBB/EG.5 period and the BA.2.86/JN.1 period, respectively. Dehydration/oral intake failure (37.2%, 111/298) and febrile seizures (16.8%, 50/298) were the predominant reasons for hospitalization. The COVID-19 vaccination rates in hospitalized children 5-11 years of age (11.1%) and 12-15 years of age (38.9%) were significantly lower than those in the general population (41.5% and 71.0%).

Conclusions: Although the clinical impact of the Omicron subvariants in children diminished over time, they continued to pose a risk. Continued efforts are needed to protect children from this evolving virus.