According to their calculations https://argoprep.com/blog/k8/go-math-grade-5-vs-argoprep/, in 63% of cases, these measures did not affect the spread of coronavirus.
In 63% of cases, the closure of borders in the second half of 2020 did nothing to contain the spread of coronavirus infection. This is the conclusion reached by mathematicians, 
whose findings were published in the scientific journal Communications Physics. According to their article, China, Russia, Spain, New Zealand and South Africa fought the most effectively against the coronavirus at this time.
“We evaluated the effectiveness of countries’ distance from each other using the approach used in physics to determine the resistance of parallel and series circuits. These calculations https://argoprep.com/blog/k8/go-math-grade-6-vs-argoprep/ showed that 63% of measures taken after June 1, 2020 were ineffective. reduced the total number of cases by about 13 million, “the researchers write.
Most countries of the world, including Russia, in the first weeks and months after the start of the COVID-19 epidemic in China, partially closed borders and introduced other restrictions on the movement of people. Epidemiologists and economists have long been interested in how these measures have prevented the spread of coronavirus and how much the situation would have changed if they had not been.
American and Chinese mathematicians, led by Jianxi Gao, Associate Professor at the Rensselaer Polytechnic Institute (USA), studied in detail how such measures influenced the spread of SARS-CoV-2 in the second half of last year. Scientists analyzed how the frequency of flight of passenger airliners and the volume of air traffic between 250 countries, geographic regions of the world, individual cities and other isolated territories have changed.
The nature of the spread of the virus between these points reminded the researchers of how current flows through complex electrical circuits, which consist of many conductors with different levels of resistance. Using this analogy, Gao and his colleagues created a computer model that described how the appearance of breaks in circuits and areas of increased resistance influenced the increase 
in the number of infections.
Having calculated in a similar way how SARS-CoV-2 was supposed to be distributed, the scientists compared the figures obtained with real data. Thanks to this, it was possible to assess how border closures and other epidemiological measures influenced the development of the second wave of the COVID-19 pandemic.
It turned out that in about 63% of cases, border closures did not bring any results. That is, the number of infections from this did not decrease, and the spread of COVID-19 around the world did not slow down, since the infection bypassed these restrictions and entered the territory of those countries that took these measures in other ways.
The remaining 36.3% reduced the number of infected by about 13 million people, and also delayed the onset of local epidemics in certain regions of the world by about 18-19 days. Measures taken by China, Russia, Spain, New Zealand and South Africa, as well as the suspension of US flights with China, have been particularly effective.
All these measures have significantly reduced the number of cases of infection or postponed the onset of the first outbreaks of COVID-19 in these countries and related territories by about 20-40 days. Scientists hope that the information they have collected will help the authorities of all countries of the world develop a more flexible approach to closing borders, which will simultaneously slow down the spread of disease as much as possible and at the same time will minimize the impact on the global economy.