We’re eight months into the COVID-19 pandemic. In the United States, cases have risen to record levels and officially hit over 100,000 confirmed coronavirus cases on November 4. More than 230,000 Americans are confirmed to have died from COVID-19 to date, with thousands of additional deaths attributable to the virus but not counted in the official statistics. Even in the face of these numbers, we’re still lacking strong federal leadership and a unified national response plan to the pandemic.
Recently, several scientists and politicians have suggested the harmful and controversial idea that perhaps it might be better to aim for “herd immunity.” In my view (and that of many other epidemiologists), this would essentially mean letting the virus burn through less vulnerable segments of the population rather than trying to prevent widespread infection via interventions including mask use and social distancing. One group of scientists in particular outlined this strategy in October, referring to it as “focused protection” in a statement called the Great Barrington Declaration. As they describe it, this approach would reduce direct harm from the virus and also inadvertent “social harm” from social distancing and lockdowns that have led to closing businesses and schools. One of their claims, which has received fervent backlash from public health experts at large, is that “the most compassionate approach that balances the risks and benefits of reaching herd immunity, is to allow those who are at minimal risk of death to live their lives normally to build up immunity to the virus through natural infection, while better protecting those who are at highest risk.” A Trump administration pandemic advisor, neuroradiologist Scott Atlas, M.D., who doesn’t have a background or specialty in infectious disease, has also embraced this strategy.
There is nothing that most of us would like more than having some semblance of normality. So why have most scientists in the field dismissed this idea of coronavirus “herd immunity” as inadequate for containing the virus and dangerous to us all? I spoke with four scientists for their thoughts.
First: What exactly does “herd immunity” mean?
“Viruses require a host to replicate,” Columbia University virologist Angela Rasmussen, Ph.D., tells SELF. “Herd immunity is when enough people in a population are immune to a given virus that the virus can’t spread any more within that population because it can’t find a susceptible host.” Deepti Gurdasani, MBBS, M.D., MPhil, Ph.D., an epidemiologist at Queen Mary University in London, notes that herd immunity additionally protects those who are not immune, like babies who can’t receive certain vaccinations yet or the minority of people who can’t receive certain vaccinations due to medical issues like a compromised immune system. “The likelihood of them coming into contact with an infected person becomes much lower,” Dr. Gurdasani explains.
There are a few different ways to achieve herd immunity with infectious diseases. One is through widespread enough vaccination in a community. Vaccines stimulate people’s immune systems in a way that protects them from getting an infection and often makes the infection less likely to be severe if they do wind up catching it. When enough people in a community get vaccinated to protect against a disease, that leads to herd immunity for that population. Unfortunately, we don’t yet have a COVID-19 vaccine to help us achieve this goal.
A far less ideal route to herd immunity, depending on the disease in question, is if enough people in a community get the illness and develop antibodies that prevent the same infection in the future, even temporarily. This isn’t a guarantee with every infectious disease. For instance, there’s still a lot we don’t know about coronavirus antibodies and immunity—more on that in a bit.
Even when enough people getting a disease can theoretically lead to herd immunity, this leaves the population vulnerable as the non-immune population grows. For example, prior to vaccination for measles or smallpox viruses, cities would see regular epidemics of these infections that would wane as communities reached local levels of herd immunity. Several years later, once enough babies had been born to create a large enough population of vulnerable individuals, the viruses would again sweep through. The advent of vaccination allowed communities to maintain herd immunity levels, as people can now receive vaccinations for many diseases in childhood. This keeps the level of susceptible individuals in the population low enough to achieve herd immunity—as long as vaccination rates are high enough. The fact that the U.S. now has outbreaks of measles due to insufficient vaccination rates in some areas is proof of this.
Why is the idea of COVID-19 herd immunity so flawed and dangerous?
In theory, “focused protection” would allow us to reach COVID-19 herd immunity by allowing people at “minimal risk of death” from the virus to live their lives as usual, while we enact even more protective measures for the most vulnerable people, who would then remain largely uninfected. In reality, there are a number of reasons why the very premise of this “focused protection” strategy is dubious.
Many experts take issue with the Great Barrington Declaration’s idea that “current lockdown policies are producing devastating effects on short and long-term public health.” Dr. Gurdasani notes that this sets up a false equivalence between the idea of COVID-19 control, economic protections, and protections for health services. “The truth is that these are all linked. Countries that have controlled COVID-19 well have done better economically,” Dr. Gurdasani says. “Similarly, health services overwhelmed with COVID-19 cannot provide routine care. The only way to protect our society and our economy is by controlling COVID-19.”
Nahid Bhadelia, M.D., MALD, an infectious disease physician at Boston University School of Medicine, also notes that lockdowns are not the primary strategy we’re using for COVID-19 control, and the public health community generally agrees that they’re not desirable. “Lockdowns are a reflection of last-ditch efforts required when you let infections run rampant in a community and you have gotten to a point where health systems are overwhelmed,” Dr. Bhadelia says.
Beyond the premise, experts argue that the actual implementation of this strategy would fail for a number of reasons as well.
“First, ‘vulnerable people’ is not limited to just the elderly,” points out Rasmussen. She notes that approximately 30 to 40% of the U.S. population has a risk factor for COVID-19: heart disease, diabetes, asthma, a compromised immune system, etc. “There are no details to how we would protect these people other than requiring them to stay in lockdown indefinitely, and no solutions given for how to support them,” Rasmussen says.
Further, Dr. Bhadelia adds that separating the “vulnerable” from the rest of society is, essentially, impossible. “Both our lived experiences and data say that we cannot separate the vulnerable from others. We share homes and workplaces with them.” She notes that the best way to protect the vulnerable is instead by keeping community transmission down in the first place. That means continuing with prevention measures like social distancing and masking. While the Great Barrington Declaration says “simple hygiene measures, such as hand washing and staying home when sick should be practiced by everyone to reduce the herd immunity threshold,” it doesn’t say anything about continuing to use measures like masks and social distancing as part of the focused protection strategy. Instead, it notes that “those who are not vulnerable should immediately be allowed to resume life as normal.” But in a November 6 interview for JAMA Network, one of the authors of the declaration, Jay Bhattacharya, M.D., Ph.D., a professor of medicine at Stanford University and research associate at the National Bureau of Economics Research, appeared to walk that back in some ways. “[With focused protection], you should social distance when you can, definitely use masks when you can’t social distance, hand-washing—I think all of those mitigation measures are really important,” he said. “I think it’s a mischaracterization to say that we say, ‘Let it rip.’ I don’t want to create infections intentionally. But I want us to allow people to go back to their lives as best they can with the understanding of the risks they’re taking when they do it.”
Reaching herd immunity also requires people who are out working and interacting socially to become infected. We could be in for a long wait, suggests Emma Hodcroft, Ph.D., a molecular epidemiologist at the University of Basel in Switzerland. “It’s highly likely that not everyone in the non-vulnerable group would be keen to get infected,” she tells SELF. “If they stay home and continue wearing masks, it could take a long time to reach herd immunity,” or we might never reach it.
Then there’s the fact that the outcomes from a COVID-19 infection are not simply recovery or death. Even among the “young and healthy,” Rasmussen explains that the popular notion that these people “uniformly have mild or asymptomatic cases is completely false.” She notes, “While the fatality rates for younger adults with no pre-existing conditions are lower, significant numbers of these patients have severe enough disease to require hospitalization.” And even if they survive, they may find themselves as COVID-19 “long haulers:” a substantial proportion of patients who are still experiencing symptoms long after they have cleared the initial infection. This can happen even in people who have mild infection. Rasmussen cautions, “Death is not the only negative outcome of COVID-19 infection, and it is dangerous to suggest that because an individual is unlikely to die that they should not take steps to protect themselves from infection.”
Additionally, while advocates of focused protection suggest that the majority of the population could have some sense of normalcy, what about those who are vulnerable? As Hodcroft notes, that would include older people and many communities of color: “We need to consider whether asking these people to isolate from society will compound the disadvantages many already experience in society.”
Finally, Dr. Bhadelia adds that the idea of COVID-19 herd immunity “plays on pandemic fatigue and is making [individuals] feel like they can let their guard down.” If a considerable amount of the population returns to pre-pandemic levels of activity, this will lead not only to additional deaths from COVID-19 but also secondary effects of the pandemic, including hospitals being overwhelmed and unable to provide adequate care for other conditions.
Is infection-based COVID-19 herd immunity actually even possible?
“Focused protection” depends on a long-term outcome of herd immunity as the result of widespread COVID-19 infections. But is this even possible?
Frankly, we’re not sure. Dr. Bhadelia cautions, “We don’t yet have a firm handle on what effective immunity for COVID is and how long immunity from natural infection lasts.” While it does seem that most people develop antibodies following infection, how long they are protective is unclear. None of the knowledge we have so far “is solid enough to let infections simply run rampant on purpose through our society,” Dr. Bhadelia says.
Dr. Gurdasani adds that we know reinfection can occur, but we still don’t understand how common that phenomenon is or the factors that lead to it.
Even if it’s possible to achieve herd immunity with natural infection, it would come at a devastatingly high mortality cost. Rasmussen notes that we are nowhere near the number of infections necessary to meet even the lowest estimates of the herd immunity threshold. Some estimates suggest that at most, 10-15% of the U.S. population has antibodies, she notes, which would mean at least 85% of people in the country would still be susceptible to infection. “If we assumed that the lowest threshold of 40% [infection] is what we need to achieve for herd immunity, that would mean tripling or quadrupling the number of new cases, which would mean that the U.S. would have 600,000-800,000 additional deaths at minimum,” Rasmussen says. Even if the mortality rate may be lower now than earlier in the pandemic (which isn’t yet certain), herd immunity would still result in a significant number of deaths. Not only would that be devastating, it would also be completely unnecessary.
What are our options besides herd immunity?
“The evidence gives us a clear roadmap for what needs to happen to control COVID-19,” Dr. Gurdasani says. She recommends additional public health investment in testing and contact tracing, and also notes that the government needs to create “financial packages that give the public security to be able to comply with regulations,” including quarantine and isolation. This kind of support has been largely absent in the U.S. coronavirus response. We also need stricter policies surrounding mask-wearing. Unfortunately, in the U.S., many states still lack state-wide mandates. Anthony Fauci, M.D., director of the National Institute of Allergy and Infectious Diseases, recently suggested a nationwide mask mandate, as have many other public health experts.
Hodcroft adds that “once cases are low, mild interventions like masks and social distancing, paired with a real investment in testing and tracing and quick reaction to any outbreaks, could keep cases low without needing extreme steps.”
Similarly, Dr. Bhadelia suggests that we should get used to a middle ground for the duration of the pandemic. “We need to exist in this band of normality between 60-90% of normal, where we use indicators such as rising cases and test positivity, and take early action to roll back some aspects of reopenings.” She notes we can then loosen or tighten these restrictions on social activities, including crowd size or indoor capacity, as numbers improve or worsen. And we need to continue to use masks, increased ventilation, physical distancing, hand hygiene, and decrease indoor gatherings as much as possible.
It’s completely understandable that people are tired of this. But the pandemic isn’t over, and pretending it is in order to get back to normal will come at a high price that will likely fail in the end. Dr. Gurdasani pulls no punches, suggesting it is “promoting an ideology that’s rooted in pseudoscience.” Rasmussen is similarly blunt about the herd immunity strategy: “This is an unacceptable price to pay for something that could be achieved without the loss of life by keeping transmission low while developing and distributing a safe and effective vaccine. In my opinion, it is grossly cynical and immoral to advocate for a plan that would lead to mass death.”