Pediatric Inpatients with Coronavirus Disease 2019 in Chiba Prefecture

<p>We conducted a retrospective study of pediatric inpatients with coronavirus disease 2019 (COVID-19) in 38 medical facilities, including in all secondary medical care areas in Chiba Prefecture affiliated to the Chiba Pediatric Disaster Network. The first five waves of the pandemic (between March 2020 and December 2021) included 155 cases (median age, 6 years 10 months) and were noted in the observational study, and the sixth wave (between January 2022 and May 2022) included 354 cases (median age; 3 years) were noted on the mailing list. Comparison of the peak months showed that there were five times as many inpatients in the sixth wave as in the first to fifth waves. In the first to five waves, 90% of the cases showed mild symptoms (fever, upper respiratory tract infection, asymptomatic), and there was only one case of severe pneumonia. On the other hand, in the sixth wave, there was a higher number of cases hospitalized with convulsions (19.5%) or croup (4.5%). Status epilepticus and cluster cases accounted for 42% and 30.4% of the patients with seizures, respectively, and three cases were diagnosed as having encephalitis/encephalopathy. A total of 13 cases (3.7%), including the three cases, required intensive care or equivalent treatment. In the sixth wave, only 2.6% of patients aged 5-11 years and 40% of patients aged ≥12 years had received both primary doses of the vaccine against COVID-19. Therefore, during the Omicron wave, the symptoms of pediatric inpatients with COVID-19 changed as compared with those during the previous waves. The vaccine coverage among hospitalized cases was low, suggesting the importance of promoting vaccination of children to prevent severe COVID-19.</p>