ABSTRACT
BACKGROUND: To combat the coronavirus disease 2019 pandemic, many countries, including Japan, implemented policies limiting social activities and encouraging preventive behaviors. This study examines the influence of such policies on the trends of 10 infectious pediatric diseases: pharyngoconjunctival fever; group A streptococcal pharyngitis; infectious gastroenteritis; chickenpox; erythema infectiosum; hand, foot, and mouth disease; herpangina; respiratory syncytial virus; exanthem subitum; and mumps. METHODS: The research adopted a retrospective cohort study design. We collected data from Japan's National Epidemiological Surveillance Program detailing the incidences of the 10 diseases per pediatric sentinel site for a period beginning at 9 weeks before government-ordered school closures and ending at 9 weeks after the end of the state of emergency. We obtained corresponding data for the equivalent weeks in 2015-2019. We estimated the influence of the policies using a difference-in-differences regression model. RESULTS: For seven diseases (pharyngoconjunctival fever; group A streptococcal pharyngitis; infectious gastroenteritis; chickenpox; erythema infectiosum; hand, foot, and mouth disease; and herpangina), the incidence in 2020 decreased significantly during and after the school closures. Sensitivity analysis, in which the focus area was limited to the policy-implementation period or existing trend patterns, replicated these significant decreases for one of the above mentioned seven diseases - infectious gastroenteritis. CONCLUSIONS: Policies such as school closures and encouragement of preventive behaviors were associated with significant decreases in the incidences of most of the 10 diseases, which sensitivity analysis replicated in infectious gastroenteritis. To determine the long-term effects of these policies, prospective cohort studies are needed.