Vietnam defied the experts and sealed its border to keep Covid-19 out. It worked.

This story is one in our six-part series The Pandemic Playbook. Explore all the stories here.

Every January or February, Le The Linh and his wife pack their children into their car and drive 80 miles to visit family in Haiphong, a port city east of Vietnam’s capital, Hanoi, for Lunar New Year. But this time, as they reached the last stretch of the Hanoi-Haiphong Highway, a police officer approached and pointed them toward a group of guards in face masks under a makeshift tent. It was one of 16 checkpoints erected around Haiphong to control travel into and out of the city ahead of the Tet Festival holiday.

They joined a lineup of other travelers, nervously waiting for their turn in the rain. When they reached the front, the officials asked for proof of their travel plans, residency, and Covid-19 status.

“Don’t worry!” Linh exclaimed tensely. He could show, with his identity card, that they lived in an area that had no coronavirus cases recently.

The family was among the lucky ones let through. Travelers from areas near Haiphong that had recently recorded Covid-19 cases got turned away; a group of young people on motorbikes who tried to circumvent the checkpoint were arrested; still others chose not to travel at all, opting to meet family over FaceTime or Zalo (Vietnam’s answer to WhatsApp).

As the pandemic took hold last year, travel restrictions quickly proliferated — they were the second-most-common policy governments adopted to combat Covid-19. According to one review, never in recorded history has global travel been curbed in “such an extreme manner”: a reduction of approximately 65 percent in the first half of 2020. More than a year later, as countries experiment with vaccine passports, travel bubbles, and a new round of measures to keep virus variants at bay, a maze of confusing, ever-changing restrictions remains firmly in place.

But few countries have gone as far as Vietnam, a one-party communist state with a GDP per capita of $2,700. The Haiphong checkpoints timed for Tet were the equivalent of closing off Los Angeles to Americans ahead of Thanksgiving — within a country that was already nearly hermetically sealed. Last March, the government canceled all inbound commercial flights for months on end, making it almost impossible to fly in, even for Vietnamese residents.

Today, flights are limited to select groups, like businesspeople or experts, from a few low-risk countries. Everybody who enters needs special government permission and must complete up to 21 days of state-monitored quarantine with PCR tests. (Positive cases are immediately isolated in hospitals, regardless of disease severity.)

This strict approach to travel, global health experts say, is directly connected to Vietnam’s seeming defeat of Covid-19. Thirty-five people have reportedly died in total, and a little more than 2,700 have been infected with the virus during three small waves that have all been quickly quashed. Even on the worst days of the pandemic, the country of 97 million has never recorded more than 110 new cases — a tiny fraction of the 68,000 daily case high in the United Kingdom, which has a population one-third smaller than Vietnam, or the record 300,000-plus cases per day only the US and India managed to tally.

Last year, Vietnam’s economy even grew 2.9 percent, defying economists’ predictions and beating China to become the top performer in Asia.

In this series, the Pandemic Playbook, Vox is exploring the Covid-19 strategies used by six nations. Vietnam’s travel restrictions — supported by other measures, including enforced quarantining and contact tracing — help explain the country’s apparent mastery over the virus. And while the political leverage of a single-party government might have helped Vietnam respond faster and more unilaterally than others, “I don’t think this is simply about totalitarianism versus Western democracies,” said Kelley Lee, a Simon Fraser University global health professor who has been studying the impact of travel restrictions.

That’s why Vietnam is now among a few countries upending the global health community’s “almost religious belief that travel restrictions are bad,” said Lawrence Gostin, a Georgetown University global health law professor who helped write the international law governing how countries should deal with outbreaks.

“I have now realized,” Gostin added, “that our belief about travel restrictions was just that — a belief. It was evidence-free.”

Covid-19 changed the thinking about travel restrictions in a pandemic

At a time when people still thought diseases originated with imbalances in the “four humors” and doctors routinely used treatments like bloodletting, governments tried to manage travel to prevent outbreaks. In 1377, quarantine measures were introduced in Dubrovnik, on Croatia’s Dalmatian Coast, to keep out sailors potentially carrying the bubonic plague.

The law stipulated that anyone from “plague-infested areas shall not enter [Dubrovnik] or its district unless they spend a month on the islet of Mrkan … for the purpose of disinfection.” For land travelers, the disinfection period lasted even longer — 40 days.

But in the age of mass travel and globalization, it seemed virtually impossible — counterproductive, even — for cities or countries to isolate themselves. The mantra in global health became “diseases know no borders.” Just before the pandemic, 2019 was a record year for tourist arrivals. The travel and tourism sector had generated a tenth, or US $8.9 trillion, of global GDP. “It [was like] the cat’s out of the bag,” Gostin said.

Many of the measures countries tried in recent years, after the first SARS virus emerged in 2002 — including banning flights or visas for particular cities or countries, and screening for disease at airports — didn’t seem to deliver much protection.

Research on SARS, Ebola, and the seasonal flu found these targeted restrictions merely delayed infections and carried a slew of social and economic costs. They unfairly punished the economies of places that were unlucky enough to be plagued by disease, interfered with the global flows of people and goods, drove infections underground, and made it hard for aid workers and supplies to reach those who urgently needed them.

I knew these costs intimately. I grew up in Toronto, where a rare travel advisory imposed on the city by the World Health Organization in the wake of the first SARS outbreak cratered tourism to the entire province — so much so that the Rolling Stones eventually intervened with a charity concert (dubbed “SARSStock”). The measures also failed to avert outbreaks. According to a Canadian government report, putting arriving passengers through health assessments and thermal scanners didn’t root out a single case.

During the 2014-2016 West Africa Ebola epidemic and early in the Covid-19 pandemic, I co-wrote popular stories detailing this evidence and arguing against the use of such restrictions. And I wasn’t alone.

Bill Gates pointed out that then-President Donald Trump’s approach to Covid-19 travel bans probably made the US epidemic worse. The WHO’s International Health Regulations, an international law governing 196 countries’ responses to outbreaks, says countries should “avoid unnecessary interference with international traffic and trade” and follow the WHO’s expert advice. With every global health emergency declared after SARS, the WHO has not recommended travel restrictions.

At the same time, speaking out against travel bans had become synonymous with opposing nationalism and wall-building, said Lee. “There were these progressive, human rights values that were upheld by not using travel measures.”

But it’s now clear that the well-meaning advice and previous research findings didn’t match up with the situation the world was facing in early 2020. The new virus was different — more contagious and harder to stop. SARS-CoV-2 can be transmitted prior to the onset of symptoms, if they ever occur — while with SARS and Ebola, for example, people are only contagious when they are very ill or symptomatic.

The new coronavirus contagion inspired drastic measures. After China locked down Wuhan in January 2020, a move many called “draconian,” countries around the world scrambled and experimented with their own travel restrictions.

Only a few, though, did something that “seemed unfathomable” prior to the pandemic, said University of Hong Kong public health professor Karen Grépin: They completely closed their borders. It was an approach experts had no evidence for. “No one [had] modeled out a scenario in which borders would be shut,” she said, and stay shut.

Yet that’s essentially what happened in Vietnam — and in a few states or regions, mostly islands including Taiwan and New Zealand, that have virtually eliminated the virus.