Apr 24 2023

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) began to spread in Niigata, Japan in early 2020; however, the number of hospitalized children with coronavirus disease 2019 (COVID-19) was limited. An epidemiological survey conducted by a research group led by IKUSE Tatsuki (graduate student) and Professor SAITOH Akihiko in the Department of Pediatrics, Niigata University Graduate School of Medical and Dental Sciences, revealed that Omicron BA.1 and BA.2, variants of SARS-CoV-2, became prevalent from January 2022, leading to an increase in the number of infected children. In July 2022, the number of infected children surged as soon as BA.5 began to spread, resulting in a sharp rise in hospitalizations among infected children. In particular, many children were hospitalized due to febrile seizures, and one child (without underlying disease) died due to acute encephalopathy. To investigate the COVID-19 vaccine effectiveness (VE) against hospitalization for children infected with BA.5 in Niigata, we found that completed COVID-19 vaccination reduced the risk of hospitalization (VE 75%).

Research Results

• SARS-CoV-2 Omicron BA.5 spread in Niigata Japan from July 2022.
• The outbreak of BA.5 increased the number of infected and hospitalized patients, with a notable rise in cases of febrile seizures.
• The COVID-19 vaccine reduced the hospitalizations due to BA.5 infection in children: the vaccine effectiveness against hospitalization was 75%.

Publication Details

Journal: The Pediatric Infectious Disease Journal
Title:Comparison of Clinical Characteristics of Children Infected with Coronavirus Disease 2019 between Omicron Variant BA.5 and BA.1/BA.2 in Japan
Authors:Tatsuki Ikuse, Yuta Aizawa, Takayuki Yamanaka, Satoshi Hasegawa, Takanori Hayashi, Miyako Kon, Tsutomu Tamura, Akihiko Saitoh
doi: 10.1097/INF.0000000000003894