Declining Incidence of Kawasaki Disease During the COVID-19 Pandemic: A Time Series Analysis.

Background: In 2020, Taiwan experienced a dramatic disruption of daily life due to measures aimed at limiting the spread of coronavirus disease 2019 (COVID-19), although domestic COVID-19 cases were extremely rare. This provided a chance to investigate the change of incidence and possible triggers of Kawasaki disease (KD) without the interference of multisystem inflammatory syndrome in children.

Methods: This population-based study used Taiwan's National Health Insurance Research Database. To detect the change in KD incidence in children less than 6 years old during the period of social distancing policy in 2020, the autoregressive integrated moving average model was used based on seasonal variation and the increasing trend of KD incidence over the past 10 years. The trends in population mobility and common infectious diseases were also analyzed to observe their effects on KD incidence.

Results: The predicted monthly incidence [95% confidence interval (CI)] of KD in April, May and June 2020 were 5.26 (3.58-6.94), 5.45 (3.70-7.20) and 5.41 (3.61-7.21) per 100,000 person-months. The actual observed incidences were 2.41, 2.67 and 2.60 per 100,000 person-months, respectively, representing a 51.2%, 51.0% and 51.9% reduction in incident rates in the 3-month period of stringent COVID-19 mitigation measures. The trend was not proportionate to the profound decline of common infectious cases.

Conclusions: KD incidence decreased by approximately 50% during the period of stringent COVID-19 mitigation measures in 2020 in Taiwan. Human-to-human contact may be a potential KD trigger, but there are likely other contributing factors aside from infection.