Abstract
COVID-19 has caused huge losses to countries around the world, and it will not end in a short time. The lack of motivation for international joint prevention and control is one of the important reasons for the global pandemic of COVID-19. How to improve the efforts and level of international joint prevention and control has become an urgent problem to be solved. Considering the long-term and dynamic nature of international joint prevention and control, the differential game method is used to compare and analyze the optimal decisions of countries in the three scenarios of spontaneous governance, external subsidies and internal cost sharing. The results show that the optimal prevention and control efforts of countries are negatively correlated with discount rates, prevention and control cost coefficients, decay rate and risk factors. It is positively correlated with the impact degree of social benefits, the impact degree of prevention and control efforts on the level of joint prevention and control, the distribution ratio of social benefits, and the impact degree of prevention and control level on social benefits. The prevention and control efforts, joint prevention and control level, social benefits and system benefits under spontaneous governance are the lowest and highest under the internal cost sharing. The internal cost sharing will only be carried out when social benefits distribution ratio obtained reach a certain threshold. This study provides decision-making support for the joint prevention and control of countries to defeat COVID-19 under the normalization of the epidemic.