To determine the epidemiologic change in Kawasaki disease during the post-acute phase of the coronavirus disease 2019 pandemic compared with the pre- and acute phases.

A follow-up epidemiological study was conducted using data obtained from hospitalised patients with Kawasaki disease 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 Kawasaki disease was compared among these phases, focusing on monthly variation, patient age, and regional population density.

A total of 1,598 patients with Kawasaki disease were analysed. The per cent change in Kawasaki disease incidence from the pre-pandemic phase was −33.8% and −27.9% in the 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 Kawasaki disease reduction was larger in patients ≥4 years old during the post-acute phase. An association between population density and reduction in Kawasaki disease incidence was no longer observed during the post-acute phase, contrary to the result during the acute phase.

The reduction in Kawasaki disease incidence in Shiga Prefecture remained in the post-acute phase of the coronavirus disease 2019 pandemic, although seasonal variation dramatically differed from the traditional pattern. Infection prevention measures by individuals might reduce Kawasaki disease development in the children ≥4 years old.