The international spread of the SARS-CoV‑2 virus that causes the disease COVID-19 has prompted many governments to close their borders. Immigration policy plays an important role in limiting the international spread of contagious diseases.

Prior to the COVID-19 crisis, several commentators were concerned that immigrants – especially illegal immigrants – were spreading serious diseases in the United States. This blog post is the first in a series to answer the question of whether immigrants spread serious notifiable diseases other than COVID-19 in the United States. This post focuses on all pooled notifiable diseases for which there are vaccination requirements to enter the United States.

Methods

This post tests the correlation between the incidence of notifiable diseases and immigrant population shares on the state level for the 2010–2018 period. We use annual, state-level data on notifiable disease cases from the CDC’s National Notifiable Diseases Surveillance System (NNDSS), which reports the number of nationally notifiable infectious diseases and conditions by state and year. A notifiable disease is one where the CDC states that “regular, frequent, and timely information regarding individual cases is considered necessary for the prevention and control of the disease.”

Numerous diseases are reported to the CDC, but this post focuses on diseases that the U.S. Citizenship and Immigration Services (USCIS) and CDC require vaccination for prior to immigration. USCIS requires vaccination for mumps, measles, rubella, polio, tetanus, diphtheria toxoids, pertussis, haemophilius influenza type B, and hepatitis B. The CDC requires vaccination for hepatitis B, varicella, seasonal influenza, pneumococcal pneumonia, rotavirus, hepatitis A, and meningococcal disease.


Data for the foreign-born population on the state-level comes from the American Community Survey (ACS) provided by IPUMS. From the raw ACS microdata, we can identify immigrants by their nativity, citizenship status, and year of arrival. A further strength of the ACS microdata is that we can apply statistical techniques to identify likely illegal immigrants from observed characteristics in the data. Specifically, we use the residual technique of Christian Gunadi to identify illegal immigrants.

Results

To test whether states with higher immigrant shares experience higher rates of notifiable disease, we run a two-way fixed effects regression to estimate the correlation between the rate of disease per 100,000 population and the share of immigrants in a state. The regressions use state and year fixed effects and the standard errors are clustered at the state level.

Table 1 shows the results of the regressions. They are all statistically insignificant except a 1 percent increase in the share of a state’s legal immigrant population is correlated with 4.2 fewer cases of disease per 100,000 state residents, which is significant at the 5 percent level. There is no relationship between the share of a state’s population that is foreign-born and the rate of disease per 100,000 residents. There is also no relationship between the illegal immigrant share of a state’s population and the rate of disease per 100,000 residents.

Figure 1 shows the lack of a relationship between the immigrant share of the population and the incidence of these diseases on the state level. Figure 2 shows no relationship between the illegal immigrant share of state populations and the incidence of these reportable diseases.

Some immigration opponents want lawmakers to cancel the H1B visa lottery, which admits 85,000 skilled immigrants per year. Their position may reflect a belief that high-skilled immigration is especially dangerous during the COVID-19 pandemic. If so, they have the analysis backwards.

Not only do highly skilled immigrants help U.S. companies develop new technologies and innovations; many serve on the front lines of the medical response to COVID-19.

Medical professionals make up roughly 5 percent of H1B visa applicants out of the top 100 occupations. These doctors, nurses, and technicians already face overly strict regulations that limit their ability to provide care. In addition to the thousands of immigrants working in medicine, adjacent industries – including biotechnology, pharmacology, and more – rely heavily on skilled immigrant labor.

Policymakers should make it easier, not harder, for skilled immigrants to perform these critical duties. Suspending the H1B lottery is even more misguided now than it would be in normal times.

As hospital emergency rooms and intensive care units swell with patients infected with the COVID-19 virus, political leaders coordinating responses in “hot spots” are asking doctors and other medical professionals in parts of the country less impacted by the pandemic to come to the rescue. New York Governor Andrew Cuomo issued such a plea the other day. Governors are issuing executive orders that relax occupational licensing restrictions on the free movement of health care practitioners. Some are also expanding the scope of practice of various licensed health care professionals, permitting them to provide the health care services they are trained to do. Meanwhile, a large pool of doctors trained at excellent institutions outside the borders of the U.S., referred to as International Medical Graduates (IMGs), goes untapped. A cumbersome approval process begun in the 1950s places daunting obstacles in the way of IMGs who want to practice in the U.S. and keeping tight reins on the already short supply of doctors.

The process is overseen by the Educational Commission for Foreign Medical Graduates. The ECFMG is a private non-profit organization established in 1956 to “evaluate the readiness” of IMGs to enter graduate medical education programs (residencies and fellowships) in this country. (Graduates of Canadian medical schools are not considered IMGs.) The American Medical Association and the American Hospital Association soon recognized the ECFMG as the standard for evaluating IMGs entering the U.S. health care system and serving patients in its hospitals. The ECFMG obtained responsibility for visa sponsorship of Exchange Visitor physicians (J‑1 visas).

Graduates of medical schools outside of the U.S. and Canada must become certified by the ECFMG before they can enter U.S. graduate medical programs. This means they must receive their diplomas from an ECFMG-approved medical school, pass steps 1 and 2 of the 3‑step U.S. Medical Licensing Examination, complete a graduate medical education program, and then pass Step 3 of the USMLE.

State licensing requirements vary with regard to IMGs. Some require more years of graduate medical education training than they require from graduates of U.S. and Canadian medical schools before they issue them a license. Most issue licenses to graduates of U.S. and Canadian medical schools after applicants have passed step 2 of the USMLE and several don’t require these licensees pass to step 3 in order to maintain their license.

Yet IMGs who received their diplomas a while ago and have been practicing medicine outside the U.S., often for several years, must go through the same process as fresh medical school graduates. This means they must get ECFMG certification—including taking and passing all three steps of the USMLE—and go through a residency training program all over again. Then they must apply for state medical licenses. Many experienced foreign-trained doctors take positions in ancillary medical fields, such as nursing, lab technician, and radiology technician instead of starting all over again. Some even work as waiters or taxi drivers.

I worked with an Operating Room Technician (the person who passes instruments to the surgeon) from Syria who had impressed me with his knowledge and focus on the operations I perform. He would occasionally offer an excellent suggestion or insight during a technically challenging segment of the operation. I soon learned that he had been a general surgeon who practiced in Syria before coming to the U.S. He decided to divide his time between working as an OR tech and starting up a Middle Eastern restaurant rather than starting all over again.

To be sure, the quality and approach to the practice of medicine varies in different parts of the world. In some parts of the world doctors deal with a different constellation of health problems than exist in the U.S. and some may have less exposure to the technological advances that abound in the U.S. health care system. There may also be cultural differences that affect their understanding and communication with American patients. For this reason, certification organizations like the ECFMG, specialty boards (e.g., American Board of Surgery, American Board of Internal Medicine), as well as rating and evaluation services, play an important role in providing critical information to consumers of health care.

In Canada the provinces have domain over medical licensing. Some provinces grant licenses to experienced immigrant primary care physicians from certain countries to practice without having to repeat the residency program. Some also welcome medical specialists who are trained and experienced in certain other countries without having to start over.

To address the current public health emergency, several states are granting reciprocity to health care practitioners licensed in other states. Three states—Arizona, Pennsylvania, and Montana—reformed their occupational licensing laws to grant reciprocity well before the advent of COVID-19 pandemic. As I have said before, these reforms should apply to all the occupations and should be permanent—not just temporary responses to the public health emergency.

In the same spirit, states should consider granting reciprocity to health care practitioners licensed in certain other countries with reputations for quality medical education. Meanwhile, certifying organizations should include applicants’ active clinical experience in other countries as a factor in certification criteria. Finally, these changes need to be accompanied by liberalizing immigration rules for medical professionals and their families now—waiting for overall immigration reform to happen will not address the problem fast enough.

California Governor Gavin Newsom ordered all “nonessential businesses” in the state to close in response to COVID-19. The order closes all businesses except for those deemed to be part of America’s critical infrastructure. While it’s not possible to determine exactly which businesses will have to close—the order’s implementation is still being worked out—it is clear that immigrants are disproportionately likely to still be on the job this week, putting their health at risk to keep the state afloat.

The order’s language lacks the specificity to identify each particular case, but this post reviews data from the Census Bureau’s American Community Survey from 2018 (the most recent year available) to identify likely essential industries that will remain open. Overall, about 4.6 million immigrants will likely be deemed essential in California—33 percent of all the state’s essential workers. They are producing food and equipment, maintaining operations at hospitals and research facilities, and distributing supplies across the state.

Figure 1 shows the percentage of foreign-born workers in each major industry classification, including only those subindustries deemed or likely to be deemed essential. It is important to note that immigrants may play a variety of specific job duties within these industries. The share of foreign physicians in the medical industry, for example, is much higher than the share of foreign workers overall.

In 2018, California’s immigrants constituted 63 percent of the workers in essential agricultural industries, 45 percent of essential manufacturing, 40 percent of essential service sector workers, 39 percent of essential wholesale workers, 38 percent of construction, 36 percent of transportation, 33 percent of social and child agencies, 32 percent of medical facility staff, 30 percent of essential professional services, 28 percent of essential retail, and 26 percent of essential finance. Only the extraction industry and the three governmental industries—utilities, public administration, and the military—had immigrant shares below 20 percent. Overall, 27 percent of Californians were immigrants in 2018. Nationally, the share is less than 14 percent.

Table 1 provides the full list of industries that I estimated are or are likely to be deemed essential based on the governor’s order. One noteworthy essential subindustry is manufacturing of pharmaceuticals and medicines where 42 percent of its labor force in California were immigrants. Immigrants were the same share of the workforce for manufacturers of medical supplies. Another noteworthy example is grocery wholesalers—nearly half (48 percent) of its workers are immigrants in California. Similarly, 46 percent of the workers at California’s nursing care facilities—which are on the frontlines of protecting the elderly from COVID-19—are immigrants.

Immigrants are helping California survive this unprecedented challenge. They are making and distributing food, producing pharmaceuticals, and caring for the sick.

State and local medical providers are noticing a decline in immigrants’ use of health services, which they attribute to Trump administration policies:

Public-health officials say a Trump administration policy meant to discourage immigrants from using public-health resources is deterring people from getting medical treatment for fear of hurting their immigration status, making it harder to test and treat possible cases of the new coronavirus.

The rule in question, the Department of Homeland Security’s Public Charge Rule, was formally implemented on February 24, 2020. Under the rule, immigrants deemed likely to be dependent on public assistance – evidenced through use of state or local health programs targeted at poor populations – are subject to denial of permanent legal status.

An alien who is likely at any time to become a public charge is generally inadmissible to the United States and ineligible to become a lawful permanent resident. Under the final rule, a public charge is defined as an alien who has received one or more public benefits, as defined in the rule, for more than 12 months within any 36-month period.

Healthcare providers are concerned that non-citizens, fearing the threat of losing a chance at future permanent legal status, will avoid visiting doctors, thus making COVID-19 more difficult to diagnose, treat, or trace unless the disease progresses to a life-threatening stage. United States Citizenship and Immigration Services has since issued new guidance, saying:

USCIS encourages all those, including aliens, with symptoms that resemble Coronavirus Disease 2019 (COVID-19) (fever, cough, shortness of breath) to seek necessary medical treatment or preventive services. Such treatment or preventive services will not negatively affect any alien as part of a future Public Charge analysis.

Non-citizens, however, are understandably hesitant to take the revised guidance at face value. According to a Queens-based doctor, “people are wary. They believe they are having their names placed in a registry.”

Regardless of one’s views on immigration policies, one must accept that undocumented immigrants will always be present. And if policy treats these immigrants harshly, that might make them more likely to generate externalities for the native population.

Many countries have enacted travel restrictions in response to the spread of COVID-19 that originated in China. For instance, President Trump announced a partial travel ban on China in late January that went into effect on February 2, 2020. Trump’s partial travel ban exempted American citizens, lawful permanent residents, and many others. Those who returned were supposed to be medically screened and quarantined if they showed symptoms. Those quarantines and medical screening were likely inadequate as we saw after the government imposed travel restrictions on Europe and returning Americans overwhelmed the airports. At least 36 other countries also imposed travel restrictions on people coming from China at about the same time.

The goal of the travel restrictions was to slow the spread of COVID-19. Clearly, COVID-19 is just about everywhere, but the important question is whether the travel bans slowed the spread enough to either ­somewhat flatten the curve or shift the curve to the right to give enough time for health care providers, civil society, and governments to prepare. It makes intuitive sense that travel bans could have slowed the spread of COVID-19 because it originated in one part of China and spread predictably via airline routes. A recent Rasmussen poll shows that the travel bans on China and Europe are popular if they limit the spread of COVID-19.

The government has the power to limit the spread of diseases through travel restrictions. The appropriateness of a travel restriction depends upon how effective it is at reducing the spread of disease and reducing its associated costs in health, lives, and to the economy relative to the costs incurred by such a restriction. There is a growing body of academic research on travel restrictions imposed by governments in response to the COVID-19 pandemic. Although it is early and there are problems with the COVID-19 data available, travel restrictions likely delay the spread of COVID-19 in modeled simulations by up to a few weeks.

Academic Research – Epidemiological Models

Epidemiological research on how travel restrictions impede the spread of COVID-19 is almost entirely theoretical and model-based. These papers usually begin by building or adapting a model of COVID-19 transmission via transportation routes. Travel restrictions reduce or remove nodes from transportation networks, limiting the spread of the virus in destination countries where those restricted-travel nodes reside. However, these travel restrictions don’t reduce travel with all other nodes in the international transportation network. Thus, if COVID-19 is traveling between other nodes in other non-restricted countries, travel restrictions on highly-infected countries like China merely delay the spread. In other words, travel restrictions aren’t as ineffective as closing the barn door after the horse escapes, but they aren’t that much better.

A recent article in the journal Science models how China travel restrictions affected the global spread of COVID-19. They use an “individual-based, stochastic, and spatial epidemic model” called Global Epidemic and Mobility Model (GLEAM) that integrates real-world data on travel between travel nodes (cities and population centers) and the transmissibility of COVID-19.

Individuals inside of GLEAM go through several different phases with respect to COVID-19: They can be susceptible to the disease, have latent or inactive infections, be currently infectious, or are removed due to recovery or death. Those who are susceptible can acquire COVID-19 through contact with infectious individuals. Those susceptible individuals who become infected will go through a latent period and proceed to become themselves infectious. Those people who are infectious will then move toward the removed stage where they are no longer able to infect others because they were isolated, hospitalized, died, or fully recovered and acquired immunological memory. Importantly, the authors also consider how changes in the transmissibility of COVID-19 affect the spread of the disease relative to and in conjunction with travel restrictions. The authors of the paper estimated the time that an individual spends in each phase based on COVID-19 data available before the paper was published on March 6, 2020.

Next, the authors run the GLEAM model with different reductions in international travel. It’s difficult to disentangle the effect of travel restrictions imposed by different countries because of many imposed bans on travel from China at different times. Furthermore, China imposed internal travel restrictions in response to COVID-19. Thus, the authors simplify their model by considering the effects of a 40 percent and 90 percent reduction in travel to and from mainland China, both beginning on February 1, 2020. Separately, they also model how a travel ban on the city of Wuhan, which began on January 23, specifically affected the spread of the disease in the rest of Mainland China and internationally.

The Wuhan-only travel restriction reduced the international transmission of COVID-19 cases outside of Mainland China by 77 percent by early February. However, the numbers quickly rebounded. Within 2–3 weeks of the Wuhan travel restriction, the number of international cases of COVID-19 that spread to countries via airline transportation resumed its pre-Wuhan-restrictions numbers after 2–3 weeks. In other words, the Wuhan travel restriction likely reduced the spread of COVID-19 in other countries by a few weeks.

As for a February 1, 2020 travel restriction on the rest of Mainland China, the authors estimate that a 90 percent reduction in international travel would only modestly affect the pandemic’s international trajectory such that the number of cases crossing borders per day will return to the pre-Mainland China travel ban level by February 16^th. A 40 percent reduction in international travel from Mainland China beginning on February 1, 2020 would have an even smaller effect. In that scenario, the number of cases crossing borders per day returns to the pre-travel ban level on February 3, 2020.

The most important finding of the Science article is that reducing transmissibility does more to slow the spread of COVID-19 than travel restrictions. A 90 percent reduction in travel merely reduces one node in a travel network whereby COVID-19 spread. By lowering transmissibility across the world, even if only by 25 percent, the spread of COVID-19 through every node in that network is reduced greatly.

I contacted some of the authors of the Science article to ask for their code so I could replicate their model with different travel restriction scenarios, holding transmissibility constant. Additionally, I asked them to rerun their model under different assumptions and by looking specifically at the spread of COVID-19 inside of the United States. Unsurprisingly, they are extremely busy and haven’t responded yet. The biggest issue with this paper is that it’s just a model, a very useful one that increases our understanding of how COVID-19 spread, but it has not been empirically tested.

Another paper published in the Proceedings of the National Academy of Sciences looks at how Chinese-government imposed travel restrictions impeded the exportation of COVID-19 cases abroad. It found that by January 12, 2020, the daily risk of exporting a single case of COVID-19 to another country exceeded 95 percent and the likely first export occurred in December 2019. The Chinese government didn’t impose travel restrictions out of Wuhan until January 23, 2020. The authors estimate that the Chinese travel lockdown reduced the number of COVID-19 importations in other countries by about 80 percent by mid-February. They wrote:

travel restrictions cannot be expected to fully arrest the global expansion of COVID-19, but may decrease the rate of case exportations if enacted during the early stages of the epidemic … At this early stage of the COVID-19 epidemic, this decrease in exportation rates from mainland China could delay the onset of outbreaks in cities yet to be affected. This obstruction of importation events will be critical to preparing an effective public health response for when a local COVID-19 outbreak arises.

A third paper published in the Journal of Clinical Medicine ran a model about how the reduction in travel with China affected the number of COVID-19 cases in Japan, whether it delayed a “major epidemic” there, and how long the epidemic was delayed. It found that those restrictions reduced the probability of a major epidemic in Japan from 7 percent to 20 percent, which resulted in a median time delay of a major epidemic of two days. That effect was produced by reducing the number of COVID-19 cases arriving in Japan by 70.4 percent from January 28-February 7, 2020.

A fourth non-peer reviewed paper modeled the effect of Australia’s restriction on Chinese travel that was imposed on February 1, 2020. This paper is the first to look at importation bans specifically rather than reductions in overall travel. The authors found that Australia’s travel ban reduced the number of cases and deaths from COVID-19 by about 87 percent over a 400-day time period projected into the future. That is a huge effect in the model, but the paper does not consider the spread of COVID-19 to Australia from countries other than China. Including the spread of COVID-19 to Australia from other countries would certainly reduce the effectiveness of the Australian ban.

The existing literature finds that travel restrictions likely delayed the spread of COVID-19 internationally by a short period of time, from a few days to several weeks. The next question is whether these short delays made a difference.

Did the Delaying the Spread of COVID-19 Matter?

Many of the papers above model how travel restrictions delayed the spread of COVID-19, often by a short period of time. There are many reasons why travel restrictions didn’t do more to reduce the spread of COVID-19 in these models. First, many of the travel restrictions on China excluded many people. Viruses don’t discriminate by nationality, so American citizens could have brought the virus back to the United States or other countries after the travel ban. Second, the travel restriction was imposed too late. The virus had escaped China already and it was being transmitted to healthy people around the world. The travel restrictions also didn’t block travelers from other countries.

Third, the travel ban created a false sense of security that delayed other more effective methods of containing COVID-19, such as instituting social distancing sooner. In other words, the travel ban was always an ineffective policy that substituted for more effective ones like those adopted in Singapore. Other methods of reducing COVID-19 transmission are effective. To the extent that travel restrictions substituted for those policies, as they likely did in the United States, it likely undid any benefits by delaying other actions.

A delay in the spread of COVID-19 could purchase precious time to flatten the curve so that seriously ill patients won’t overwhelm hospitals, intensive care units, and die in larger numbers as a result. But that only works if the government, civil society, and business use the extra time to prepare for the coming pandemic. Like every other disaster, few were going to act until it reached certain crisis proportions. There was evidence that COVID-19 was building as a looming threat for months – in mid-February, I stocked up on emergency supplies, extra cleaning supplies, hygienic equipment, and ammunition because I was worried about COVID-19. I wasn’t the only one nor was I particularly prescient.

Conclusion

Travel restrictions, including limits on emigration and immigration, delayed the spread of COVID-19 by a few days to a few weeks. The above research papers are limited as they just model and project COVID-19 cases rather than empirically test how restrictions affected the actual spread of the disease, but they are valuable starting points in evaluating this crucial policy tool. Travel restrictions could have delayed the onset of a crisis mentality by a few weeks and shifted the curve to the right rather than flattening it. Shifting the curve to the right, in addition to preparing for a pandemic by adopting other policies to reduce transmission, could have been an effective strategy. But by themselves, travel restrictions do little but delay the onset of a crisis mentality and shift the curve to the right rather than flattening it.

As the COVID-19 spreads through the United States, the government has closed its borders to foreigners. Yet millions of immigrants already here are working every day to defeat the contagion or mitigate its economic effects. From cleaning away germs to developing cures for them to delivering needed supplies, immigrants are disproportionately engaged in the effort to defeat COVID-19. Indeed, immigrants are overrepresented in nearly every job that is critical during this pandemic.

Health Care and Diagnosis

On the front lines of this battle are the nearly 1.7 million foreign-born medical and health care workers who are caring for COVID-19 patients, according to the Census Bureau’s American Community Survey (ACS). Figure 1 shows that while immigrants composed only 13.7 percent of the U.S. population in 2018, they were 35.2 percent of the home health care aides in America (224,325), 28.5 percent of physicians (281,127), 20.9 percent of nursing assistants (365,466), 18.9 percent of health care diagnosing or treating practitioners (2,840), 18.5 percent of clinical lab technicians (73,314), 15.2 percent of medical assistants (98,383), 15 percent of registered nurses (569,534), and 14.9 percent of health technicians (24,530).

Researching Cures and Treatments

Researching cures and treatments for this virus will likely be the primary long-term solution to the crisis, and immigrants are heavily involved in the relevant fields. The United States had more than 155,000 foreign-born biomedical or chemical engineers, biological or chemical technicians, chemists, and medical or life scientists in 2018, according to the ACS. Specifically, they were nearly 40 percent of medical and life scientists (67,646) and nearly 30 percent of chemists and material scientists (32,226).

The U.S. Department of Labor has approved more than 11,000 hires of foreign workers specifically at the eight major U.S. companies researching coronavirus cures and treatments. Figure 3 below shows that—as I have detailed before—over the last decade, those eight companies have received approvals for 3,310 biochemists, biophysicists, chemists, and other scientists under the H‑1B program. They have received approvals for 2,801 statisticians to analyze the data the scientists are producing as well as 2,133 computer, database, and software support staff.

Cleaning and Disinfecting

It has never been more important to have clean work places, homes, and public spaces. A National Institute of Health study has found that COVID-19 can live on surfaces for up to 3 days, and the Centers for Disease Control (CDC) recommends cleaning and disinfecting as a “best practice measure for prevention of COVID-19.” As Figure 4 shows, immigrants specialize in cleaning occupations that prevent the spread of the disease. They are nearly half of America’s maids, a quarter of its janitors, and 22 percent of its vehicle cleaners and its supervisors of janitors.

Distribution and Delivery of Food and Supplies

The CDC recommends that Americans limit exposure to public spaces as much as possible, so households are stocking up on food and other supplies like never before to avoid trips out. The country is depending on supply chains to allow them to stay inside, and immigrants are disproportionately involved in those chains from start to finish.

Nearly 1.5 million immigrants work in delivery, shipping, and trucking, bringing products to households who need them across America. As Figure 5 shows, immigrants were 18.4 percent of industrial truck and tractor operators (139,172), 17 percent of shipping and receiving clerks (126,406), 17 percent of truck and delivery drivers (760,462), 14 percent of freight and stock workers (450,719) in 2018.

Food Production

Americans still need food to wait out this crisis, and immigrants cultivate and process a significant portion of America’s food and meat production. Figure 6 shows the foreign-born share in various agricultural and related occupations. In 2018, there were more than 700,000 immigrants in the agricultural and food or meat processing jobs. This doesn’t include the more than 200,000 foreign workers admitted to farms as H‑2A guest workers.

Other Production of Supplies

Beyond food, immigrants are also heavily involved in production of other supplies. More than 1 million immigrants worked in the production jobs listed in Figure 7. In particular, one in five paper goods machine operators were immigrants in 2018. These jobs include toilet paper, which has faced unprecedented demand in recent weeks.

Obviously, native-born Americans are still the majority of most occupations in the United States, but immigrants play an important and disproportionate role in many of the occupations that the country is relying upon to get through this tough period. Given the important roles that immigrants are playing, the country should recognize the value of immigration more today than perhaps at any other time in its history.