Narrator: Imagine dipping your child in a sacred, magical river, believing you could make them immortal, invulnerable to all harm. This is the myth of Achilles, whose mother Thetis held him by the heel as she submerged him in the River Styx, leaving one single spot unprotected. It was that one spot, his heel, where a poisoned arrow would eventually find its mark and kill him. This ancient story, like so many others, whispers a timeless and unsettling truth: perfect, absolute protection is an illusion. This deep-seated human anxiety—the desperate wish to shield ourselves and our children from a world of invisible threats—is the central question explored in Eula Biss's profound book, On Immunity: An Inoculation. Biss weaves together mythology, history, science, and her own experiences as a new mother to dissect the powerful metaphors and fears that shape one of the most contentious issues of our time: vaccination.

Narrator: The desire for invulnerability is a powerful and ancient human impulse. Biss begins by exploring myths that reveal our obsession with impenetrable bodies. Beyond Achilles, she points to the folklore of a hero who bathes in dragon’s blood to make his skin impervious to any weapon. But as he bathes, a single leaf falls onto his back, leaving a small patch of skin untouched. Like Achilles, this hero is eventually slain by a blow to his one vulnerable spot. These stories teach a humbling lesson: the body is not a fortress. The very idea of perfect, sealed-off immunity is a myth.

This myth-making becomes intensely personal with the arrival of a child. Biss describes how motherhood brought a heightened sense of both power and powerlessness. The overwhelming instinct is to protect, to create a perfect shield against fate. Yet, this instinct runs headlong into the reality that life is inherently risky. This tension fuels a deep-seated fear, particularly around decisions like vaccination, where parents feel they are making a gamble with their child's future. The fear isn't just of the needle, but of making the wrong choice—of creating a vulnerable spot, like Achilles' heel, where harm might enter.

Narrator: Our understanding of the world is shaped by the language we use, and Biss argues that our perception of vaccination is corrupted by fearful metaphors. The very words we use—a "shot" or a "jab"—imply violence and violation. This framing taps into deep-seated anxieties about purity and contamination.

Biss masterfully connects this to the vampire myth, particularly Bram Stoker's Dracula. Published in an era when germ theory was new and terrifying, Dracula embodies the fear of contagion. He is a foreign entity who crosses borders to contaminate the pure blood of the nation, spreading his curse through a bite. This fear of contamination from an outside source mirrors historical anxieties about vaccination. Early methods sometimes involved transmitting diseases, and modern fears have shifted to the chemical components of vaccines, seen as industrial pollutants invading the "natural" body. The vampire, a monster who pollutes from within, becomes a powerful metaphor for how some view vaccination—as a monstrous act that taints the body more than the disease it's meant to prevent.

Narrator: In a culture that celebrates rugged individualism, the concept of "herd immunity" often feels alienating. The word "herd" suggests mindless conformity. However, Biss reframes this idea not as a loss of autonomy, but as a beautiful, shared responsibility. She introduces this through a personal story about her father, a doctor with O-negative blood, the "universal donor." He taught her that responsibility extends beyond oneself, just as a driver is responsible not only for their own car but for the cars ahead and behind.

This ethic of shared responsibility is the true heart of herd immunity. It’s not about being a faceless animal in a herd; it’s about contributing to a collective "banking of immunity." Each vaccinated person makes a deposit, creating a resource that protects everyone, especially the most vulnerable who cannot be vaccinated. Biss argues we should think of our collective immunity less like a herd and more like a garden. It’s a shared space that we must cultivate together. The 2003 SARS outbreak serves as a powerful example. The virus was identified in just a few weeks because laboratories across ten countries shared information and worked collectively, achieving something no single lab could have done alone. Our immunity, Biss suggests, is like that: a profoundly collective enterprise.

Narrator: Humans are notoriously bad at assessing risk. We tend to fear spectacular, rare dangers while ignoring common, everyday threats. Biss explores this paradox through the story of triclosan, the antibacterial agent that became ubiquitous in soaps and hand sanitizers. Fueled by fears of novel flu viruses, consumers embraced these products, believing they were creating a safer environment. Yet, evidence suggests antibacterial soap is no more effective than regular soap, and triclosan is a pervasive environmental chemical with unknown long-term effects.

This illustrates a pattern of "paranoia and neglect." We fixate on the perceived, and often exaggerated, risks of highly regulated interventions like vaccines, while overlooking the real and unregulated risks of chemicals in our daily lives. Biss presents stark data to make this point: the risk of encephalitis from a measles infection is about 1 in 1,000. The risk of encephalitis from the MMR vaccine is about 1 in 3 million. Yet public fear remains stubbornly focused on the vaccine. This is because our fears are not purely rational; they are shaped by a desire for control. In a world of invisible threats, from industrial pollutants to viruses, focusing on a single, avoidable act like vaccination provides an illusion of agency, even if it means we are afraid of the wrong things.

Narrator: The traditional understanding of the immune system is based on a military metaphor: a war between "self" and "nonself." In this view, the body is a nation-state constantly defending its borders against foreign invaders. But this model is flawed. Our bodies are teeming with "nonself" organisms, like the bacteria in our gut, that are essential for our survival. A fetus is "nonself" to its mother, yet her body doesn't attack it.

Biss introduces a more elegant and accurate concept: immunologist Polly Matzinger's "Danger Model." This model proposes that the immune system isn't primarily concerned with whether something is foreign, but whether it does damage. Matzinger uses the analogy of a police force. The "self vs. nonself" model is like police who kill any new migrant, regardless of their behavior. The "Danger Model" is like police who ignore tourists and immigrants until they start breaking windows. It is the act of causing danger that triggers an immune response. This reframes the body not as a battlefield, but as an ecosystem—a garden. Its goal isn't to kill all outsiders, but to cultivate a healthy, balanced environment.

Narrator: Ultimately, On Immunity dismantles the idea that our bodies are private property, to be managed in isolation. The book’s single most important takeaway is that immunity is a public space, a shared reality. We are not sealed-off fortresses but porous, interdependent gardens. Our health is inextricably linked to the health of our neighbors, our communities, and our environment. We are, as Biss powerfully states, each other's environment.

Eula Biss leaves us with a profound challenge to our modern, individualistic mindset. She asks us to look past our fears and the seductive myths of perfect purity and control. The real question is not how to build higher walls around ourselves, but how to tend our shared garden more thoughtfully. Can we embrace our collective vulnerability and recognize that caring for each other is, in the end, the only true way to care for ourselves?