Five years ago, President Donald Trump ordered that U.S borders be closed to any foreigners arriving from China after the outbreak of the COVID-19 virus. Over the two months that followed, travel across the world would be restricted in unprecedented ways. In the absence of better options for controlling a deadly and highly contagious virus, hardening borders was one of the few tools governments had in their arsenal—despite the risk of human and civil rights violations. Some of the restrictions would last for three years or more.

COVID thus became a global experiment on the effectiveness of travel restrictions in reducing the spread of a contagious disease. Health researchers will be studying the impact for decades. In some places where borders were relatively easy to control—such as island nations including Australia, Japan, and New Zealand—the measures almost certainly reduced both COVID infections and deaths, but not without enormous costs. Couples, families, and friends living across national borders were separated, sometimes for years. Container ship workers were trapped for months at sea unable to disembark. Some countries even barred their own citizens from returning.

The lessons learned from COVID should inform more effective future public health responses to reduce the enormous collateral consequences of closing borders. Instead, the world seems to be moving in the opposite direction; the United States especially is taking actions that will leave countries with few choices other than border closures to deal with future pandemics. As Martin Cetron, head of the Division of Global Migration and Quarantine at the Centers for Disease Control and Prevention for more than a quarter century, told my coauthor Laurie Trautman and me for our new book on the COVID border closures: "This is the first time in my experience of 30 years that we are coming out of a crisis less prepared than when we went in."

Preparing for the Next Crisis

Returning President Donald Trump took several actions in his first week that reinforce the fears of Cetron and others. The president again announced his intention to pull the United States out of the World Health Organization (WHO), which will weaken the world's ability to respond quickly to novel disease outbreaks before they spread to become global threats. He halted funding for the President's Emergency Plan for AIDS Relief (PEPFAR) program to help treat HIV patients in high-burden countries, increasing the likelihood of wider spread that could produce drug-resistant strains. Trump's new executive orders on immigration and border control also go well beyond the Title 42 provision used during COVID to refuse entry to asylum seekers at the Mexican and Canadian borders. To justify those actions, his administration has asserted the constitutional authority—independent of congressional statutes—to close the nation's land borders against an "invasion." A primary rationale, among several others, is that migrants are "potentially carrying communicable diseases."

The United States will do little to help prevent the next pandemic, but when it arrives the government will shut its borders

The message behind these actions is clear: The United States will do little to help prevent the next pandemic, but when it arrives the government will shut its borders earlier, tighter, and—depending on the nature of the disease—for longer than they were during COVID. The rest of the world could have little choice but to follow along.

COVID should have been a case study on the limitations of borders for preventing disease transmission. Trump bragged in his first term that his February 2020 decision to block entry from China saved "millions of lives" —but the disease was already spreading widely in the United States. Despite the border restrictions, more Americans would die from COVID than in any other advanced economy. Countries that did far better—such as South Korea and Taiwan—combined flexible border restrictions with effective domestic public health interventions such as masking, widespread testing, contact tracing, and closely monitored isolation and quarantine. Even Europe, which lifted travel restrictions earlier than regions outside the tourist-dependent Caribbean, suffered far fewer COVID deaths than the United States. Border restrictions likely helped slow the spread of the virus in some countries, but only when coupled with a more comprehensive public health response.

The Risks of Border Closures

Since the first recorded border closure to prevent the spread of the Black Plague by the Adriatic port city of Ragusa in the fourteenth century, public health and border control have had an uneasy marriage. Borders were never designed for disease control; modern borders are built to screen goods and people, not viruses, but too often, they are the only tool that governments have.

The World Health Organization had historically discouraged border closures during pandemics, fearing that the threat of restrictions would prevent countries from early reporting of disease outbreaks that could help avoid global pandemics. It is not an idle fear—when South Africa reported its breakthrough discovery of the fast-spreading omicron variant in November 2021, giving the rest of the world a valuable head start in developing countermeasures—it immediately faced fresh travel bans from the United States, the European Union, Japan, and others. South Africans and others in the region were locked in just at a time the rest of the world was opening up due to higher levels of vaccination.

A passenger tries to find a flight as several airlines have stopped flying out of South Africa, due to the spread of the COVID-19 variant Omicron, in Johannesburg, South Africa, on November 28, 2021. — A passenger tries to find a flight as several airlines have stopped flying out of South Africa, due to the spread of the COVID-19 omicron variant, in Johannesburg, South Africa, on November 28, 2021. REUTERS/ Sumaya Hisham

Some of the worst human and civil rights violations in the name of public health occurred late in the pandemic as a result of border closures. In January 2022, when about 90% of its population had been vaccinated, New Zealand was still rationing the return of its nearly 1 million overseas citizens. Charlotte Bellis, a New Zealander working in Doha, Qatar, was one of 30 pregnant women who could not get space in the limited number of hotel quarantine rooms the government allotted. Only after an embarrassing public campaign—Bellis was offered refuge by the Taliban in Afghanistan, where she had previously worked as a journalist—did the government relent and permit her to come home.

The United States blocked nearly 3 million migrants under the Title 42 restrictions, turning back asylum seekers crossing from Mexico despite the U.S. legal obligation to hear such claims. The measure was the last COVID border restriction lifted anywhere in the world, the Biden administration and U.S. states fearing that its removal would lead to a migrant surge at the border.

Such long and costly border closures in the name of disease control was exactly what the WHO had worked to avoid. As CFR Senior Fellow David Fidler has written, the International Health Regulations, first codified in 1969, were intended to "ensure the maximum security against the international spread of disease with minimal interference with world traffic."

COVID destroyed that formula, and it will be hard to resuscitate. There is plenty of blame to go around. China's failure to report the COVID outbreak in a timely fashion meant that the virus had spread across the country and to other regions of the world before an international response was mobilized. Many countries felt they had no choice but to restrict travel to try to slow further infections.

The border closures also turned out to be popular as the public looked for governments to do something to protect them from the deadly virus. As late as November 2021, after vaccines had been widely administered in the wealthier countries, 56% of those surveyed in 28 countries—including more than 60% of Americans—still favored maintaining closed borders to keep out the virus.

COVID also largely removed what had long been the biggest obstacle to border restrictions—their impact on international trade. With the growing use of technology and expansion of monitoring at most national borders, countries found ways to keep trade moving while barring what was considered nonessential travel. Some, such as the United States and Canada, declared all trade to be essential, accepting the additional COVID infections that would be carried by truckers and cargo pilots. Countries pursuing zero-COVID strategies—such as Australia, China, and New Zealand—found ways to transfer incoming cargo to domestic rail lines and trucks without permitting entry by the foreign workers delivering cargo to their borders.

At best, border measures are a supplement to strong domestic public health interventions

The result was that COVID's impact on international commerce was surprisingly modest. Trade slowed sharply in the middle of 2020 as national economies went into lockdowns, but by early 2021 trade volumes had recovered to pre-pandemic levels. Most of the persistent supply chain bottlenecks were created by soaring demand for electronics, exercise equipment, and other products craved by those shut in during the lockdowns or otherwise fearful of leaving home.

Better Approaches Needed

All this will make border restrictions a far more usable tool for governments when the next pandemic strikes. A best-case outcome would be a revision of international health guidelines to acknowledge the public health value of border closures under some scenarios but placing reasonable limits on their use. The issue, however, was kept off the agenda during last year's renegotiation of the International Health Regulations. It will similarly be absent if countries can somehow manage to conclude the new global Pandemic Treaty, which is focused on issues of intellectual property rights and vaccine distribution.

A better approach will need to come from outside the United States. South Korea showed that effective domestic health interventions can produce superb outcomes without border restrictions. South Korea required quarantine by incoming travelers, which stopped tourists from coming, but largely avoided hard border closures except a brief ban early in the pandemic on travelers from Hubei Province, China. The European Union, after an early tranche of national border closures when the virus was spreading in Italy, found ways, while taking sensible precautions, to coordinate on border measures that allowed those living and working across borders to resume their lives.

At best, border measures are a supplement to strong domestic public health interventions. Countries should be working to shore up their domestic capacities and coordinate on the use of travel restrictions where they may be needed. Instead, led by the United States, border restrictions will again be the first response of choice when the next pandemic inevitably hits. The results are certain to be no better than during the COVID outbreak five years ago—and possibly worse.

U.S. customs vehicles stand near a sign reading that the border is closed to non-essential traffic, at the Canada-United States border crossing, in Lansdowne, Ontario, Canada, on September 28, 2020. — U.S. customs vehicles stand near a sign reading that the border is closed to non-essential traffic, at the U.S-Canada border crossing, in Lansdowne, Ontario, Canada, on September 28, 2020. REUTERS/Lars Hagberg

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