NHK reported online on Tuesday evening that according to a simulation conducted by a group of experts led by Hokkaido University Professor Nishiura, if Japan allows entry of 10 COVID-19-positive visitors per day, a large-scale outbreak will occur in three months with almost 100% probability even if they undergo PCR testing upon arrival and they self-quarantine for two weeks at hotels because some infected individuals will slip through these protocols. According to the simulation, the probability of a large-scale outbreak that would require the government to declare a state of emergency in three months under the scenario is 98.7%. Meanwhile, the group also reportedly found that if the GOJ successfully limits the number of foreign visitors with COVID-19 entering Japan to two per day by taking such measures as imposing strict restrictions on entry from nations that are facing an outbreak, the probability of a large-scale outbreak will be 58.1%. Similarly if the number is limited to one person per day, the probability will be reduced to 35.3%.
Professor Nishiura reportedly pointed to the need for entry restriction itself since there is a limit to preventing infection with COVID-19 through quarantine. He also pointed out that although the GOJ is planning to relax entry restrictions, it has failed to explain with clarity to what extent it is aware of the risk of infection when the entry restrictions are lifted. He reportedly added that quarantine and entry restrictions fall under the jurisdictions of different ministries, and stressed that the government should improve inter-ministerial coordination, analyze the risk of COVID-19-positive visitors, and swiftly create a system to restrict entry or relax restrictions.