Sustained Reduction in Kawasaki Disease During The Post-Acute Phase of The Coronavirus Disease 2019 Pandemic: A Follow-Up Study in Shiga, Japan

Objective: To determine the epidemiologic change in Kawasaki disease (KD) during the post-acute phase of the coronavirus disease 2019 (COVID-19) pandemic compared with the pre- and acute phases. Study design: A follow-up epidemiological study was conducted using data obtained from hospitalized patients with KD in Shiga Prefecture, Japan. The study period was divided into three phases: pre-pandemic (January 2015 to March 2020), acute pandemic (April 2020 to December 2020), and post-acute pandemic (January 2021 to December 2022). The incidence of KD was compared among these phases, focusing on monthly variation, patient age, and regional population density. Results: A total of 1,598 patients with KD were analyzed. The incidence of KD (per 100,000 person-years) was 105.6 [95% confidence interval 99.8–111.8], 69.9 [57.9–84.5], and 76.1 [68.1–85.2] in the pre-, acute, and post-acute phases, respectively. Monthly variation during the post-acute phase dramatically differed from that observed in the pre- and acute phases, with the highest incidence in August and the lowest in April. The reduction in KD incidence was larger in older age groups during the post-acute phase. During the post-acute phase, an association between population density and decrease in KD incidence was no longer observed, contrary to the result during the acute phase. Conclusions: The reduction in KD incidence in Shiga Prefecture remained after the acute phase of the COVID-19 pandemic, although seasonal variation dramatically differed in the post-acute phase from the traditional pattern. Our data indicate that for older children, minimal infection control measures might reduce KD development.