東京大学政策評価研究教育センター

CREPEDP-134

Number CREPEDP-134
Publication Date November 2022
Title Heterogeneous Risk Attitudes and Waves of Infection
Author Daisuke Fujii, Taisuke Nakata, and Takeshi Ojima
Abstract Many countries have experienced multiple waves of infection during the COVID-19 pandemic. We propose a novel extension of the SIR model, a CSIR model, that can endogenously generate waves. In the model, cautious individuals take appropriate prevention measures against the virus and are not exposed to infection risk. Incautious individuals do not take any measures and are susceptible to the risk of infection. Depending on the size of incautious and susceptible population, some cautious people lower their guard and become incautious—thus susceptible to the virus. When the virus spreads sufficiently, the population reaches “temporary” herd immunity and infection subsides thereafter. Yet, the inflow from the cautious to the susceptible eventually expands the susceptible population and leads to the next wave.
Keywords COVID-19, epidemiology, SIR model, waves, periodic solution
Other information Paper in English (28 pages)