Scientists are remarkably optimistic about their ability to develop a safe and effective vaccine for the coronavirus within the next six to 12 months. But even if those hopes come true, it is far from obvious that enough people will be willing to take the vaccine to halt the pandemic.
Long before COVID-19 arrived, a worrying number of parents refused to immunize their children against measles. The new virus has inspired an even louder movement of science deniers: Americans who have embraced quack remedies, ridiculed social-distancing measures, and decried masks as tyrannical. Could they stage a successful revolt against a mass-vaccination campaign?
It certainly seems possible. In a recent CBS News poll, half the respondents said they would wait before getting a vaccine; 20 percent said they would refuse it altogether. And so a growing number of articles warn about the possibility that, even once a safe and effective vaccine is available, America may fail to reach herd immunity—the point at which community spread ends because enough of the population is no longer susceptible to infection.
Wondering whether the pandemic might rage on because millions of Americans spurn a perfectly good vaccine, I recently contacted leading public-health experts from around the country. What they told me was largely reassuring. A coronavirus vaccine won’t meet the same resistance as the measles vaccine, because although few Americans have direct experience with the dangers posed by measles, dying patients and empty shops daily remind us of the urgency of vanquishing the current pandemic. And because the coronavirus is far less infectious, the country would achieve herd immunity even if a sizable minority of Americans refused to vaccinate themselves against COVID-19.
In other words, as long as America proves capable of delivering a safe and effective vaccine to its citizens, it will contain the coronavirus. Without a doubt, some Americans will refuse to get vaccinated. But their number is likely to be too small to defeat the effort to end the pandemic. “If anything,” Jeffrey Flier, the Higginson Professor of Physiology and Medicine at Harvard University and a former dean of its medical school, told me, “you are more likely to have fights over who gets to access it first.”
When I called Flier to ask how worried we should be about people refusing to take a vaccine for COVID-19, the question did not surprise him. Without skipping a beat, he rattled off a long list of factors that might drive a significant minority of Americans to refuse the shot. As recent months show, a general skepticism about science and scientists has now deeply infected the American mainstream. A lot of people, Flier warned, fear that ”these scientists want to control my life.” Among many Americans, this mistrust of scientists is compounded by an even stronger distrust of authority. Some people, Flier worried, would reject any medical treatment offered by the government—especially if it involved some form of mandate.
Others may refuse the vaccine for more calculated reasons. Since younger people are less susceptible to dying or falling gravely ill, for example, they may decide that the vaccine isn’t worth the trouble. Many Americans may worry about whether a new vaccine that was developed at unprecedented speed could really be safe. Thinking that they are being used as guinea pigs, they might decide to await the impact of mass immunizations.
Other researchers with whom I spoke echoed many of the same concerns about people’s possible resistance to taking a vaccine, especially if its rollout is botched. To avoid such mistakes, Michele Andrasik and Chris Beyrer, who are among the leaders of the COVID-19 Prevention Network, an initiative by the National Institutes of Health, have already started to test different messages for communicating the benefits of immunization to the public. As Beyrer told me, early results indicate that an emphasis on the importance of the vaccine for revitalizing local communities will be crucial. “A lot of people are feeling very isolated,” he said, “so we are building a lot around solidarity: ‘We are all in this together!’”
Because of the influence of the anti-vaxxer movement, the vaccination rate for measles has dropped so low in certain areas of the country that children from Brooklyn to Santa Monica have contracted the potentially life-threatening disease. It is natural to fear that the same could happen with the coronavirus. But this ignores the fundamental differences between the two diseases. “You can’t just take the anti-vaxxer mentality you see with measles,” Flier told me, “and apply it to the situation we face with COVID.”
Despite occasional local outbreaks, measles has mostly been eradicated in the United States. This is one of the great achievements of 20th-century medical science. But it also comes with an ironic drawback: Because most people have never experienced the disease, or witnessed the damage it can wreak in their friends or relatives, they don’t have a sense of how dangerous it is.
To make things worse, many people realize that they can free ride on the efforts of others. Because enough Americans have been vaccinated against measles for the country to enjoy herd immunity, any one person can forgo the treatment without running a serious risk of contracting the disease. Undermining society’s efforts to keep the disease under control is deeply immoral—especially since a small proportion of children cannot safely take the vaccine, because their immune system is compromised—but it might not be individually irrational.
The case of the coronavirus is far different. Since Americans do not yet enjoy herd immunity against COVID-19, free riding is impossible, and getting the vaccine helps protect the health of each individual patient. The sooner you get immunized, the earlier you can go about your life without the risk of contracting a very serious illness (or passing it on to your friends and relatives). Though some people will, against all reason, choose to endanger themselves and their loved ones, the selfish case for getting a COVID-19 vaccine will be much more compelling.
What’s more, the risks posed by the coronavirus are very much on the mind of most Americans. Far from being a virtually extinct disease whose dangers are only chronicled in medical textbooks, COVID-19 has seriously sickened or killed hundreds of thousands of Americans in the past few months.
All these reasons help explain why the experts I consulted are optimistic that most Americans will ultimately choose to immunize themselves. As Beyrer, the Desmond M. Tutu Professor of Public Health and Human Rights at Johns Hopkins University, told me, “The whole country, and the whole world, is invested in getting a vaccine.”
Polio, rather than measles, may be the best historical precedent for predicting what will happen once a vaccine for COVID-19 becomes available. “Older Americans still have a memory” of polio, Beyrer said. “The vaccine allowed them to go back to having a childhood, and not having to be afraid of mixing with other children.” In that sense, the immense suffering of the past few months may offer a bitterly ironic silver lining, he said: “This disease has touched almost everyone. Tragically, that is a reason why there will be a very different take-up to this vaccine.”
But will enough people get it? What happens if, as the CBS poll suggests, one in five Americans refuses to cooperate?
The answer to this question provides the most definitive reason that the anti-vaccine movement is unlikely to scupper herd immunity for COVID-19. The percentage of the population that needs to be immune against a disease for it to stop spreading depends on how infectious it is. This is what makes measles, an extremely infectious disease, so susceptible to the whims of a small minority. On average, each person who contracts measles infects 12 to 18 others. (The exact number depends on a host of circumstances, including the density of the affected area, and can vary even more widely, according to a recent study in The Lancet.) This is why a relatively small number of anti-vaxxers can wreak terrible damage: If as few as 10 percent refuse to protect themselves (or their children) against measles, Beyrer told me, a population may lose its herd immunity—with potentially devastating consequences for those who are too young or too sick to get a vaccine.
But the novel coronavirus is far less infectious than measles. Instead of 12 to 18 people, the typical COVID-19 patient infects two to three. As William Moss, the executive director at the International Vaccine Access Center at Johns Hopkins University and a professor in its School of Public Health, told me, “It’s not as transmissible a virus, so the herd-immunity threshold is much lower.”
According to the experts I spoke with, the threshold for herd immunity for COVID-19 is likely to fall somewhere between 50 and 70 percent of the population. Since about one in 20 Americans is likely to have suffered from COVID-19 by the time a vaccine becomes available, this means that somewhere between 45 and 65 percent of the American population will need to be vaccinated.
In the case of measles, herd immunity requires an almost total social consensus about the utility of vaccines. As some children have painfully learned, such near unanimity is difficult to sustain. But in the case of COVID-19, anti-vaxxers would have to convert a much larger proportion of Americans in order to have a similarly devastating impact on our collective health. Unless one in three—or even one in two—Americans refuses a vaccine that would allow them to go back out into the world without fear and protect their loved ones from a deadly pandemic, the U.S. is likely to reach herd immunity.
Again and again, the coronavirus has defied expectations about how it is likely to behave. We would therefore be well advised to reckon with the possibility that things could once again break against us. Perhaps this virus is not only uniquely suited to disrupting human civilization but also unexpectedly adept at beating our attempts to immunize people against it.
But though we should look to the future with due caution, unfounded pessimism is no more reliable a guide to the world than unquestioning optimism. After a harrowing year, the moment when we—hopefully—identify a safe and effective vaccine against COVID-19 will be a crucial turning point. Though many logistical challenges will remain, the path out of this terrible pandemic will then be brightly lit.
This year has shown us how steep a price pandemics exact for both individual irresponsibility and political incompetence. But though we must reckon with the social failings that have made the pandemic so deadly, especially in the United States, we should also remember the strengths that might ultimately allow us to vanquish it: individual rationality and collective ingenuity.
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