The COVID-19 pandemic resembles a tragedy of the commons—a situation where people have little incentive to invest in conserving or producing a resource because they cannot prevent other people from using or taking it. The results are overconsumption, underinvestment, and ultimately the depletion of the resource.

Classic examples of the tragedy of the commons include overfishing, air pollution, water pollution, and overgrazing. In the case of COVID-19, the resource is the public spaces that we all share with one another. Many of these are privately owned, such as grocery stores, salons, bars, restaurants, theaters, and concert venues. Others are not, including public schools, public subways, public parks, and city sidewalks.

Disease microbes treat human bodies as a resource they use for reproduction. To prevent the microbial overexploitation of the health commons requires germ management. The best way to prevent invasive viruses, bacteria, and fungi from wreaking havoc is to enclose the commons of human bodies by erecting barriers to forestall the transmission of germs from person to person. Good fences make good healthy neighbors.

Social distancing measures, facial coverings, and—hopefully soon—safe and effective vaccines are the best ways to enclose the health commons against the COVID-19 scourge. Let’s take a look at each of these barriers to coronavirus transmission.

Social distancing measures include limiting large gatherings of people, closing buildings, and canceling events. They include encouraging people to telecommute for work; closing bars, restaurants, theaters, gyms and schools; canceling sporting events and concerts; and advising people to try to maintain a personal space of six feet when interacting with others in public.

Let’s consider the case of closing restaurants and bars. Many individual restaurateurs and bar owners would surely voluntarily assume the costs of such pandemic precautions as limiting indoor service, spacing tables further apart, setting up physical barriers, and restricting the number of customers served at a time. Taking such costly precautions also benefits the entire economy, and people who are not customers, by reducing the risks of an outbreak and enabling recovery to begin. But if all other businesses are paying for such costly measures, a competing restaurant has an incentive to free-ride off a healthier pool of customers by easing its own social distancing rules. The tragedy of the health commons occurs as social distancing erodes among competing dining and drinking establishments, revving up the epidemic again. There is, therefore, a strong case for compensating the businesses that shut down to implement social distancing policies and their employees who had to stay home.

Social distancing really works. A new review of the initial effects of social distancing measures adopted prior to May 2020 in 10 countries, including the U.S., found that they “appeared to have [a] tremendously positive effect on limiting the COVID-19 spread.” In the absence of a robust testing, tracing, and voluntary quarantining system (which is another way to enclose the health commons), the easing of social distancing measures beginning in May by various states afforded the coronavirus greater access to the health commons. As a result, increasing virus transmissions fueled a second higher wave of diagnosed infections in June and July. That wave has fortunately not produced the same level of mortality that the first wave did. The lower case fatality rate likely results from a combination of factors, including improved treatment regimens, expanded medical capacities, and the fact that these diagnoses are concentrated among less immunologically vulnerable younger Americans.

How about the widespread wearing of facial coverings? A primary route of transmission of COVID-19 is likely via small respiratory droplets, and the virus is known to be transmissible from presymptomatic and asymptomatic individuals. A just-published study in JAMA Internal Medicine reports that asymptomatic carriers of the coronavirus are likely to be just as infectious those who experience symptoms of the disease.

Again, accumulating evidence strongly suggests that the ubiquitous wearing of face masks does protect people from becoming infected. A June study in the Proceedings of the Royal Society A notes that some countries where face mask use by the public is around 100 percent have experienced significantly lower rates of COVID-19 spread and associated deaths. A July preprint reviewing the literature on the efficacy of facial coverings to prevent disease transmission notes that reducing the spread of disease “requires two things: first, limit contacts of infected individuals via physical distancing and other measures, and second, reduce the transmission probability per contact.” The researchers conclude find that “the preponderance of evidence indicates that mask wearing reduces the transmissibility per contact by reducing transmission of infected droplets.” They calculate that near universal masking could spare as much as trillion dollars in losses from the U.S. economy.

A June study in Health Affairs took advantage of a natural experiment by comparing COVID-19 transmissions between March 31 and May 22 among states that had adopted universal mask mandates and those that didn’t. While the researchers advise caution with respect to their calculations, they find that mandating face mask use in public is associated with a decline in the daily COVID-19 growth rates and estimate that mask wearing may have averted 230,000 to 450,000 cases before May 22. Interestingly, they find “no evidence of declines in daily COVID-19 growth rates with employee-only mandates.”

In any case: Whatever we think of governmental mask mandates, surely we can all agree that private businesses are free to adopt policies requiring that their customers wear face masks.

Masking works primarily by acting as a “source control.” That is, it prevents pre-symptomatic and asymptomatic infected folks from inadvertently transmitting their viruses to healthy people. Last week, an article in the Journal of General Internal of Medicine suggested that wearing facial coverings also likely protects uninfected people by reducing the amount of virus they ingest when they encounter an infected person. Lower viral exposure likely results in milder forms of the disease.

But the best way to enclose the health commons against the virus is the rollout of safe and effective vaccines. Fortunately, it looks increasingly likely that such vaccines will become available before the end of this year.

The goal of vaccination is to achieve herd immunity. Vaccines do not produce immunity in everyone, so a percentage of those are vaccinated remain vulnerable. Herd immunity works when most people are immunized against an illness, greatly reducing the chances that an infected person can pass his microbes along to other susceptible people, such as infants who cannot yet be vaccinated, immunocompromised individuals, or folks who have refused the protection of vaccination. Right now, epidemiologists typically estimate that the COVID-19 threshold for herd immunity is around 60 to 70 percent.

People who refuse vaccination are free-riding off herd immunity. Anti-vaccination folks are taking advantage of the fact that most people around them have chosen the minimal risk of vaccination, thus acting as a firewall protecting them from disease. But if enough refuse, no firewall gets built and the health commons remains open the virus. Disturbingly, a new Gallup poll reports that while 65 percent of Americans would take the personal responsibility to protect themselves and others by getting a COVID-19 vaccination 35 percent say that they would not. That is uncomfortably close to what epidemiologists believe is the threshold needed to enclose the health commons against COVID-19 by means of herd immunity.

With respect to the COVID-19 virus we are all living in an open access health commons. Given the data, we should all, as free and responsible individuals, seek to protect ourselves and others by enclosing that commons through social distancing measures, by wearing face masks, and by getting inoculated once safe and effective vaccines become available.