Is There ‘No Scientific Proof’ That Social Distancing Prevents the Spread of Coronavirus?

On April 22 2020, a KUSI News item (“USC Professor Joel Hay says there is no scientific proof social distancing prevents spread of coronavirus”) appeared containing a claim that proved particularly popular among people who opposed COVID-19 social distancing measures — orders typically described as “stay at home,” “shelter in place,” “lockdown,” or “quarantine.”

That link was shared to Reddit’s r/Coronavirus on April 23 2020:

The post appears to have been removed from that subreddit after being tagged as “low quality” information.

KUSI’s ‘USC Professor Joel Hay says there is no scientific proof social distancing prevents spread of coronavirus’

In the blurb, Hay’s comments were described as his individual “stance” on social distancing measures, and he appeared to suggest that the approximate month of social distancing prior to his KUSI appearance yielded no mitigation in the spread of coronavirus:

USC Professor Joel Hay joined Good Morning San Diego to discuss his stance on how to get people back to work.

Hay said that there is no proof that social distancing works for diseases like coronavirus. He backed up this point by saying we have been social distancing for over a month, and there are no signs that it is helping us contain the spread of the virus.

Plus, Hay explained that there was coronavirus cases in California much earlier than we originally thought, before social distancing guidelines were implemented. Has the spread of coronavirus changed? Hay says we don’t really know, but asks, why are we shutting everything down if we have no proof it works?

But, Hay says people with pre-existing conditions, elderly, etc. should isolate themselves. He doesn’t believe we need to isolate the young and healthy, as proven by Sweden.

In the third of four brief paragraphs, Hay is paraphrased as saying that “we don’t really know” if “the spread of coronavirus has changed.” Moreover, Hay’s position is summarized as questioning why social distancing is being observed if “we have no proof it works,” as well as what appeared to be his opinion that the “young and healthy” ought to not be affected by the various social distancing measures in place across the United States and elsewhere in the world.

Video Portion of the Segment

A six-minute, thirty-seven second clip of Hay speaking was embedded (and available separately on YouTube); we were unable to find a transcript for the segment.

At the beginning, an anchor describes ongoing debate between people who supported reducing all social distancing measures for economic reasons, and people who supported continuing the measures to continue reducing the spread of novel coronavirus.

A truncated version of the clip was shared by @KUSINews on April 22 2020:

In the clip, Hay claimed that “all these people … their entire intervention of social distancing” is “based on no evidence.” He goes on to say the novel coronavirus has “been around for a long time” and that there is “no proof social distancing has reduced transmission.”

Throughout the clip, the anchor challenged Hay’s claims with statements about transmission rates and an ostensible reduction in anticipated rates of COVID-19 cases. Hay then claimed that despite a number of pregnant women testing positive for COVID-19, no newborns had tested positive, repeatedly saying — again — that there is “no proof” that social distancing had any effect on COVID-19 transmission. (The relevance of that particular statement was neither clear nor clarified as the interview progressed.)

At the end of the clip, Hay said in his concluding remarks:

… don’t isolate the young and healthy … Sweden proved that’s how you get the herd immunity, that’s how you get the social mixing, that’s how we’ve done it naturally for millions of years … what is this nonsense?

In short, the sum total of Hay’s claims amounted to “here’s what I think about this,” not “here’s proof what I’m saying is true.”

Hay’s Stance on COVID-19 and Social Distancing

Finally, Hay directs viewers to a poll hosted on his personal website, which was also host to a number of opinion/editorial links and entries illustrating Hay’s anti-social distancing stance.

On the landing page of the site were a list of hyperlinks to content on Hay’s site or other news organizations (typically politically partisan ones). Hay appeared to be curating links and content in support of his clear viewpoint: harm caused by social distancing measures globally was not preferable to harm caused by allowing the virus to spread by ending the measures, orders, et cetera.

Both in the video and on his website, Hay arguably engaged in a “gish gallop” (defined by RationalWiki as “the fallacious debate tactic of drowning your opponent in a flood of individually-weak arguments in order to prevent rebuttal of the whole argument collection without great effort”) on both KUSI and his site, and employed cherry picking to select research supporting his stance while discarding all other notable evidence.

Hay’s Background and COVID-19 Measures

Hay describes himself as a “health economist,” a classification under “economics,” not “medicine.” Pharmaceutical company Sanofi-Aventis describes “health economics” in the following way [PDF]:

Economics is the science of scarcity. The application of health economics reflects a universal desire to obtain maximum value for money by ensuring not just the clinical effectiveness, but also the cost-effectiveness of healthcare provision. Achieving ‘value for money’ implies either a desire to achieve a predetermined objective at least cost or a desire to maximise the benefit to the population of patients served from a limited amount of resources. This requires services to be evaluated for ‘cost-effectiveness’.


It is universally acknowledged that the technical ability of healthcare systems to provide care (the wide array of new and expensive health technologies available) far exceeds the ability of any healthcare system to afford all such technologies. Once healthcare decision-makers have accepted the need for choice, they must inform that choice by prioritising competing interventions through the analysis of their costs and benefits. However, it is important to recognise that healthcare exhibits a range of special characteristics that will fundamentally affect such analyses. Health economics reflects a universal desire to obtain maximum value for money by ensuring not just the clinical effectiveness, but also the cost-effectiveness of healthcare provision.

Quarantining the ‘Young’ and ‘Healthy’

On April 28 2020, we explained the subject of quarantine (versus isolation), and the manner in which it is used to mitigate or suppress the spread of disease during events such as the COVID-19 pandemic:

All accepted definitions of quarantine include the fact that it affects people who could spread disease from possibly doing so, not people who necessarily have demonstrated they have contracted a given disease. As of late April 2020, the most recent estimates indicate between 25 and 50 percent of SARS-CoV-2 carries are asymptomatic, and that just over one percent of all Americans were tested — precisely the sort of situation for which quarantine is typically employed.

‘What is This Nonsense?’ and the History of Social Distancing

Going by Hay’s remarks, viewers might conclude that COVID-19 marked the first time in history any or all countries enacted stay at home, quarantine, or social distancing measures.

This is, of course, not the case — concurrent and ongoing reporting on the COVID-19 pandemic frequently explained efforts throughout history to mitigate or suppress the spread of disease with quarantines. In an April 2020 fact check, we described the widespread use of such measures during the 1918-1919 Spanish Flu pandemic, and subsequent findings about the impact of the measures:

A 2010 historical analysis published in the journal Public Health Reports provided one example of documentation antedating COVID-19 in which social distancing measures were examined and quantified. In the article’s synopsis, its authors addressed the intentional use and presumed efficacy of social distancing during the Spanish Flu pandemic, concluding that such measures “significantly reduced” rates of mortality:

The Spanish influenza arrived in the United States at a time when new forms of mass transportation, mass media, mass consumption, and mass warfare had vastly expanded the public places in which communicable diseases could spread. Faced with a deadly “crowd” disease, public health authorities tried to implement social-distancing measures at an unprecedented level of intensity. Recent historical work suggests that the early and sustained imposition of gathering bans, school closures, and other social-distancing measures significantly reduced mortality rates during the 1918–1919 epidemics. This finding makes it all the more important to understand the sources of resistance to such measures, especially since social-distancing measures remain a vital tool in managing the current H1N1 influenza pandemic. To that end, this historical analysis revisits the public health lessons learned during the 1918–1919 pandemic and reflects on their relevance for the present.

Another article we found from 2012 (“Controlling epidemic spread by social distancing: Do it well or not at all”) hinged heavily on the balance between economic and epidemiological outcomes:

We ascribe an economic cost to the loss of social contacts, and weigh this against the economic benefit gained by reducing the impact of the epidemic. We study the sensitivity of the results to two key parameters, the individuals’ attitude to risk and the size of the awareness neighbourhood.


Depending on the characteristics of the epidemic and on the relative economic importance of making contacts versus avoiding infection, the optimal control is one of two extremes: either to adopt a highly cautious control, thereby suppressing the epidemic quickly by drastically reducing contacts as soon as disease is detected; or else to forego control and allow the epidemic to run its course. The worst outcome arises when control is attempted, but not cautiously enough to cause the epidemic to be suppressed. The next main result comes from comparing the size of the neighbourhood of which individuals are aware to that of the neighbourhood within which transmission can occur. The control works best when these sizes match and is particularly ineffective when the awareness neighbourhood is smaller than the infection neighbourhood. The results are robust with respect to inclusion of long-range, small-world links which destroy the spatial structure, regardless of whether individuals can or cannot control them. However, addition of many non-local links eventually makes control ineffective.

Epidemiologists vs. Economists on Social Distancing

Historical evidence only goes so far when discussing COVID-19 and the duration of social distancing. An April 4 2020 piece written by University of Michigan epidemiologist Abram Wagner explained why the general public might not fully understand the patterns of infection after such measures were introduced, and why those misperceptions jeopardized the slowed spread of COVID-19:

Americans might begin to wonder if these social distancing measures are working if the case numbers keep climbing. The problem is that the number of reported cases is not the same as the number of people who are infected. It takes time for people to develop symptoms, seek treatment and get tested and for the results to come back. So the effects of social distancing might not be obvious from the numbers for a while. As an epidemiologist at the University of Michigan, I can assure you that staying at home is one of the most effective ways to slow the spread of COVID-19.

A key reason for the delay between people severely restricting their movements and a drop in the number of new cases is that COVID-19 can have a long incubation period, the time between getting infected and becoming sick. The average incubation period is around 5 days, but it can be as long as 14 days or more. This means that a person infected before a stay-at-home order might not get diagnosed until days later.

Testing is another factor in the delay between the start of social distancing and seeing the results. Many Americans don’t even know if they’ve been infected with the new coronavirus – SARS-CoV-2 … scientists have found asymptomatic and presymptomatic transmission of COVID-19.

Although Hay asserted (without evidence) that no proof exists that social distancing works, this is untrue. Wagner referenced data from a relatively recent outbreak of infectious disease, and the trajectory of compliance with suppression measures:

If Americans see increases in case counts and believe that their own actions are ineffective, they might be less inclined to follow through on social distancing. This could lead to increased contact among people, which could make it more difficult to bring the pandemic under control. Hopefully widespread testing and faster test results will lead to a more accurate understanding of who is and is not infected with the disease, not unlike what South Korea has accomplished so far. In the meantime, Americans should not take an increase in COVID-19 cases to mean that their sacrifices aren’t worth sustaining.

There’s No Question That Social Distancing Works, and There Is a Long Historical Precedent

The KUSI interview was predictably well-received among people arguing against lockdown measures; among many faulty assertions made by Hay was that there was “no proof” social distancing worked as intended. That claim was easily disproved by a mountain of research into the spread of disease during previous pandemics, and epidemiologists — the actual experts on the efficacy of social distancing as a bulwark against COVID-19 were making no such calls to “end social distancing.” Economists typically argued that the financial cost of a shutdown outweighs the reduced mortality (and conversely that there is an acceptable number of preventable deaths that the public should overlook for the sake of the economy), but that was not the same as the demonstrably false assertion that no evidence supports social distancing.