Updates on Coronavirus Disease 2019 in Children in Japan

Abstract

This review provides updates on coronavirus disease 2019 (COVID-19) in children in Japan by summarizing published data. By the end of March 2022, Japan had experienced 6 waves of COVID-19 outbreaks. Over this time, the clinical features presented among children have changed in the context of the predominant variants. Although the COVID-19 pandemic affected children in terms of medical, physical and psychosocial aspects, the clinical outcomes have been favorable in Japan compared with those in some European countries and the United States, which may be partly due to a lower incidence of multisystem inflammatory syndromes in children and obesity. The COVID-19 vaccine has been available for children; however, the vaccination rate in children 5–11 years of age is lower than that in older children due to the government’s lack of an active approach in this specific population. Further action is needed to improve the overall vaccination rates in children.

Comparison of clinical characteristics of COVID-19 in pregnant women between the Delta and Omicron variants of concern predominant periods

“…In the present study, the SARS-CoV-2 vaccination coverage of pregnant women differed greatly, ranging from 3.6% in the Delta VOC period to 64.3% in the omicron VOC period. At the time of the Delta VOC period, SARS-CoV-2 vaccines had already been approved for two doses for adult population [ 33 ], and the cause of this difference is unknown. However, we speculate that the higher vaccine efficacy against the Delta VOC [ 14 ] prevented a significant proportion of hospitalizations during this period.…”

“…Therefore, we could not investigate about the association with predominant VOCs and pregnancy outcomes. Several meta-analyses revealed the negative impacts of maternal COVID-19 on pregnancy outcomes, such as increasing preterm birth, preeclampsia, and stillbirth [ 33 , 34 ]. However, the information regarding the effect of predominant VOCs on fetal outcomes is still limited and further study is warranted to reveal the unreported effects in Japan.…”

Acute and Postacute Clinical Characteristics of Coronavirus Disease 2019 in Children in Japan

“…In Japan, severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) Delta and Omicron variants became predominant in August 2021 and January 2022, respectively. 5 Hence, we divided the survey periods by VOC into the pre-Delta period (from February 2020 to July 2021), the Delta period (from August 2021 to December 2021), and the Omicron period (from January 2022 to April 2022). Then, we analyzed the influence of age and the predominant SARS-CoV-2 variant on the clinical manifestations and severity of pediatric COVID-19 patients.…”

Kawasaki disease following SARS-CoV-2 infection: Stronger inflammation with no increase in cardiac complications

“…The first case of MIS-C in Korea was reported in October 2020 ( 31 ), and as of February 2022, a total of 19 cases have been confirmed ( 32 ). In Japan, MIS-C was reported in 10 children during the Delta wave and in 8 during the Omicron wave as of March 27, 2022 ( 33 – 35 ). Contrary to the higher incidence of KD in Korea and Japan, the incidence of MIS-C is far lower than that in other regions, such as the United States or Europe.…”