In the series The Walking Dead, the protagonist, Rick Grimes, learns not only to grow food, but also to operate life or death and repair all kinds of vehicles to escape the attack of the undead. The fiction continues in real life. In the book Zombie: Survival Guide, Max Brooks explains in detail the skills necessary to survive a zombie attack and, on the Internet, there are plenty of videos, courses and books to learn all the skills necessary to survive in a hostile environment, including nuclear attacks, natural disasters or a global pandemic. Despite this, not all of us have the time or the necessary capacity to acquire these skills, and even less so in the middle of the August holidays. The good news is that our survival does not depend on it, just as the well-being of countries does not depend on each territory being able to supply itself with everything its inhabitants need. In the same way that it is not necessary to know how to build a bivouac [para dormir al raso en la montaña]Whether it's repairing a car engine or cauterizing a wound to survive from Monday to Sunday, countries do not need to produce each and every product they consume. In this sense, the Covid-19 health emergency has shown that no country can deal with the coronavirus alone and that, in a crisis situation, self-sufficiency does not work. Between February and April 2020, 90 countries took measures to liberalise trade. Although many, including the European Union, restricted the export of certain medical products in the first months of the pandemic, most, including European countries, facilitated the procedures for purchasing them abroad, reducing or eliminating import tariffs. The import of products for the treatment of Covid-19 increased rapidly. What's more, overcoming the production restrictions imposed during the lockdown, supermarkets have continued to sell and there has been no shortage of food or products, domestic or imported. However, it is true that this crisis has highlighted the fragility of global supply chains. Products are no longer manufactured in one country and global trade is based on the purchase and sale of components, which originate in one country and cross multiple borders to another, where they are assembled and from where they are exported to the rest of the world for consumption. Two weeks after the Chinese government quarantined Wuhan, Hyundai had to stop its car production in South Korea due to a lack of devices from China. The European Union, for its part, was unable for months to provide masks to all its citizens, despite doubling the number purchased abroad, and had to increase its internal production, which already accounts for 60% of the masks in the community territory. The world, therefore, is debating whether globalization has gone too far and whether, in the division of functions, countries have lost the technical capacity to manufacture essential and apparently simple products such as masks. The debate is welcome, but it needs figures and analysis. Regarding the Covid-19 crisis, these analyses indicate that no country could have dealt with the virus alone. According to the OECD, Germany, one of the world's largest producers of medical supplies, imported 0.72 euros for every euro it exported in coronavirus-related medical supplies. Similarly, for every dollar the United States imports in medical supplies for the treatment of Covid-19, American companies exported 0.75 dollars. China, where half of all the world's masks are produced, imported medical protective equipment from Europe when the virus was still confined to Wuhan. It can therefore be concluded that the vulnerability associated with imports of certain products, such as medicines or medical supplies, has not been conditioned by whether or not a country has been able to produce these products, but by the magnitude of the crisis and the lack of diversification of its suppliers, whether they are national or foreign companies. In other words, when all imports of a product come from a single country, a natural disaster, a political dispute or a pandemic can put the purchase of these products at risk. To reduce this vulnerability, it is possible to establish reserves of medical products, in the same way that oil reserves were created in the 1970s; harmonising product standards to make it easier to find alternative suppliers, or removing tariffs on imports of medical products. In the case of the European Union, vulnerability is minimised by the fact that only 1% of all its imports come from a single country. Repatriating the production of certain products to Spain or the EU will not only make these products more expensive, but will make us more fragile if something happens, since we will be conditioned only by our own capacity to react. In the pandemic, globalisation has helped us through imports from foreign companies that have been able to produce the necessary goods when our factories were closed. In this crisis we have needed respirators, masks and medical protection systems, but in the next one dialysis equipment, certain foods or medicines made from a specific compound may be required. This is why a production system made up of multiple companies in various geographical locations is able to react more quickly to situations such as the coronavirus crisis. Research into the Covid-19 vaccine is a good example of how collaboration between countries is enabling processes to be optimised and progress to be made more quickly. Unlike Rick Grimes' character, the key to building a productive system capable of withstanding natural disasters, conflicts or pandemics is diversification and not self-sufficiency. Having the productive and industrial capacity of the rest of the world makes each of the countries that make it up stronger and more agile, not more fragile, in order to protect their citizens. Óscar Guinea is an economist at the think tank European Centre for International Political Economy. On Twitter: @osguineaIsabel Pérez del Puerto is a journalist and communicator in finance for development.