Why Were the Emergency Measures Tougher Than Expected? On the Influences of Mathematical Model Analysis

This paper examines how the analysis based on the mathematical model of infectious diseases influenced the choice of measures in the first emergency declaration in the spring of 2020. Specifically, we investigate the causes and implications of selecting measures that deviated from the ex-ante assumptions established at the enactment of the Act on Special Measures for Pandemic Influenza and New Infectious Diseases The ex-ante scenario was that strong measures, entailing restrictions on private rights, would last one to two weeks, but this was determined in consideration of legal and social aspects, rather than medical grounds. The duration of the first emergency (one month) exceeded the ex-ante scenario, driven by the anticipation of a surge in severe cases beyond ventilator capacity. However, the model utilized failed to adequately account for real social contact structures, leading to an overestimation of epidemic size, thereby prolonging the duration of measures beyond the initial scenario. The explanation provided by infectious disease experts, based on the mathematical model, suggested that new infections could be contained within the capacity of contact tracing over a one-month period with an 80% reduction in contact opportunities, but not with a 70% reduction. However, this analysis was scientifically unfounded and improperly manipulated, with errors such as conflating infected and newly infected persons, mislabeling 65% as 70%, tilting the line indicating 100 persons, assuming inequalities, and biasing the addition of days before contact reduction to one side only. All of these manipulations skewed the results in favor of the 80% reduction, which the experts strongly advocated, over the alternative. Correcting these manipulations would demonstrate that even with a 70% reduction, the target could be achieved within the timeframe, rendering the 80% reduction unsupported by scientific evidence. Thus, accepting the analysis provided by infectious disease experts uncritically in studying the policy process of the time is ompromised, because it begins with a misconception of the facts.