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Ten months into the SARS-CoV-2 pandemic, there is mounting frustration that life is not back to “normal.” Many U.S. schools and businesses remain closed, people are hesitant to fly and enjoy vacations, and in many places, restaurants and indoor activities are sharply limited, with severe economic consequences.

With patience wearing thin, it may be tempting to consider policies that give us a return to normalcy, whatever the consequences.


This wishful thinking describes the recent political consideration of herd immunity, a public health term that refers to the threshold at which enough people in a community are immune to an infectious disease so it cannot spread if reintroduced. Historically, herd immunity has been achieved only through the use of vaccines. Trying to achieve herd immunity against SARS-CoV-2, the virus that causes Covid-19, without a vaccine is an idea that has come into vogue. But it is a misguided and dangerous approach that would not bring life back to normal, and would lead to the deaths of 500,000 or more Americans.

Department of Health and Human Services Secretary Alex Azar testified last week that “herd immunity is not the strategy of the U.S. government.” Yet President Trump has asserted that with increased SARS-CoV-2 spread “you’ll develop herd — like a herd mentality. It’s going to be — it’s going to be herd developed — and that’s going to happen.” Scott Atlas, an adviser on the White House Coronavirus Task Force, has espoused such a plan.

Herd immunity protects those with vulnerable immune systems. Here’s how. Alex Hogan/STAT

It has also been reported that the White House “embraces” the Great Barrington Declaration, a statement written by three infectious disease researchers who have since been joined the thousands of co-signers. This political statement, funded by the American Institute for Economic Research, a libertarian think tank, calls for allowing “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,” until many people are infected by SARS-CoV-2 and recover — achieving the herd immunity threshold.


The declaration proposes a vague set of “Focused Protection” measures for the vulnerable older adults, including testing of nursing home staff. The declaration is simplistic and doesn’t acknowledge the scientific uncertainties of immunity to the virus, the long-term consequences of infection, or that young people can — and do — develop severe cases of Covid-19 and sometimes die from it.

This declaration profoundly underestimates the suffering that would result if this strategy were to be enacted.

The declaration glosses over scientific realities. The young are not invulnerable to the effects of SARS-CoV-2 infection. While children tend to have fewer hospitalizations and milder disease than adults, more than 1,000 have suffered from multisystem inflammatory syndrome in children (MIS-C) which leads to vascular complications and shock. Risk factors for severe Covid-19 in people of all ages include obesity and diabetes — which encompasses 40% of the U.S. population.

Death is not the only measure of Covid-19’s impact. Many non-elderly adults infected by SARS-CoV-2 have become “long-haulers,” experiencing long-term health effects like cardiovascular and respiratory problems. About 20% to 35% of U.S. patients with Covid-19 have lingering symptoms two to three weeks after recovery. Risk factors may not be obvious, with at least 10 football players developing a heart condition called myocarditis after infection. It is not known what additional long-term consequences may result — we still have a lot to learn about this new disease.

Achieving herd immunity would require recovered people to have lasting immunity, but scientists do not yet know how long immunity lasts. Reinfections are rare, but have occurred. Though much has been learned about the immune response to SARS-CoV-2, and the importance of antibodies and T cells, there is no test a person can take to determine if they are immune or to know if their immunity has waned.

Without a vaccine, the human cost to reach herd immunity would be profound. There is a range of models for herd immunity thresholds, depending on how much weight is given to vaccine efficacy, degree of social distancing, and how long immunity lasts. Most models, however, indicate it would require 60% to 80% of the population to be infected, which would be a minimum of nearly 200 million cases in the U.S. alone. Approximately 8% of the U.S. population has been infected with SARS-CoV-2, based upon the prevalence of antibodies, so significantly more infections would be required, leading to at least 510,000 deaths based on the current fatality rate and equations for herd immunity.

Relying on herd immunity alone would overwhelm hospitals. And infections, hospitalizations, and deaths would continue to disproportionately impact Black people, Indigenous people, and people of color — something the declaration conveniently omits.

Calls for a herd immunity strategy have been met with strong resistance from experts, including the 12,000 members of the Infectious Diseases Society of America, hundreds of signatories to the John Snow Memorandum, and 17 public health organizations, led by the Trust for America’s Health. Anthony Fauci of the National Institutes of Health has condemned the idea as “nonsense and very dangerous.”

No country has successfully achieved herd immunity from the coronavirus. The example of Sweden’s approach, with minimal social distancing and masking measures coupled with restaurants and schools remaining open, should serve as a deterrent rather than a model, with significant deaths tolls and blows to health care systems.

The U.S.’s goals should echo the science-based, layered approaches of countries such as South Korea and Germany. Leaders in public health note that it is a false choice to either do nothing to prevent infections or shut everything down. The U.S. needs a strategic approach with the commonsense precautions that we’ve heard over and over again. These measures and an eventual vaccine can save lives and livelihoods.

The path ahead cannot rely on magical thinking: herd immunity is not a plan.

Gigi Kwik Gronvall is a senior scholar at the Johns Hopkins Center for Health Security. Rachel West is a postdoctoral scholar with the Center for Health Security and the Department of Molecular Microbiology and Immunology at the Johns Hopkins School of Public Health.

  • For those who are skeptical a vaccine can be available in six months I wish to point out, there were vaccines in May – tested on animals, proven to work – should they have been mass produced and given to the public? Maybe not, but they could have done human challenge testing of them – and we would have known, by July, if they prevented disease.
    What is my point? Simple, the medical establishment, in most of the countries which have the capability of making vaccines, forbade the aggressive testing which might have made them available by now. Hippocrates was WRONG – though actually it is not his fault, he was right at the time, but the first tenet of the Hippocratic Oath, “First, do no harm” made sense then, but no longer does – if you have a good theoretical reason something will work, and a strong need – and a worldwide semi shut down of everything qualifies for that – then you take some chances.
    As it is, we halt our testing when one person might have had a bad reaction, while 500 die, and we lose a couple billion, every day the virus controls us – and the media tells us it is Trump’s fault – Maybe, in the sense that he did not demand human challenge and other aggressive research- but it is the medical establishment that wants to be cautious.
    The dictatorships meanwhile race ahead of us- China and Russia have vaccines. The media will not talk about them much- they probably have undergone extensive challenge testing already- does the country that kills people for practicing yoga and to get their organs hesitate to do that?
    As for herd immunity – no, you can’t get there without a lot of people dying – but it is clear the lockdowns, against championed by the medical establishment, should have been focused on high risk people – the 18 to 30 year olds should have been put in a Civilian Conservation Corps , isolated, and encouraged to infect each other

  • I have no doubt about SK’s good performance in containing the virus.
    I have reservation about Germany’s.
    Germany’s total number of cases of 370 thousand and death of 10 thousand, in a country with 83 million people, may seem low because it was usually compared to other European countries ( UK, Spain Italy, France, Belgium, Netherlands) and US
    Germany ranked 18th in terms of total cases and 20th in death worldwide.
    Germany daily cases went up to as high as 8000 and averaged a few thousands per day.
    Statistics don’t lie.

  • For the simple minds touting the Swedish approach out there.
    Sweden has 5-10 times the death toll (adjusted by population) of neighboring Scandinavian countries, and Germany as well, so far. And on par with the US. Which, if anything, is an indication of the American sloppy response to the pandemic. And still quite far from achieving any actual herd immunity. And the Swedish economy went into recession anyway, as the world economy around it has slowed down.
    Besides, the US is not Sweden. Swedes are educated, civilized and socialists and behaved more responsibly anyway than most ignorant, gross and selfish Americans, by voluntarily implementing the common sense behaviors to reduce the spread of the virus.
    Herd immunity would make sense only if multiple wave of infections would occur and no vaccines would become available. Instead, it is realistic to consider vaccines will be available in six months, or so. luckily for Swedish authorities, there are about 4k unsatisfied customers who will not have a chance to complain.
    And BTW, the real death toll in the US is already somewhere between 300k-400k

    • Six months seems optimistic considering that multiple trials have recently been paused. Also, we don’t know how effective vaccines might be. And even if we did have a vaccine tomorrow, we aren’t all going to get vaccinated at the same time. This is not to say that I endorse a herd immunity approach, but I think a lot of people are far to optimistic about Covid

    • We need to consider the offsetting deaths from increased poverty, depression resulting from social isolation, long-term impact on education, etc. The US government cannot continue to add trillions to its already enormous deficit without severe long-term consequences to our economic health, therefore, additional relief bills are going to be limited leading to increased poverty, in particular to people of color. There are inherent risks to just living. Consider that in 2019 alone 38,800 Americans lost their lives in car accidents (1.3 million globally) – how do we tolerate such an annual loss of life?? We could save nearly all of these lives if reduced the speed limit to say 5 mph. We don’t do so because of the significant implications to our economy and how we want to live our lives. It’s time for a frank and honest discussion of risks of COVID-19 albeit unpleasant.

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