The summer of 2010 was a bummer for many reasons. Heat waves stewed the East Coast into submission. Harvey Pekar and Tony Judt died. WikiLeaks dumped so many anxiety-inducing classified Afghan war documents that this sprig of dialogue from “Gravity’s Rainbow” seemed freshly plucked: “Everything is some kind of plot, man.”  That summer’s most sinister happening, the troll under the bridge to sanity, was the Deepwater Horizon oil leak in the Gulf of Mexico. The writer Eula Biss was home with an infant son in the wake of that mean summer. When she learned that the plastic on her baby’s mattress was possibly toxic, it was one shred of paranoia too many.  “If our government can’t keep phthalates out of my baby’s bedroom and parabens out of his lotion,” Ms. Biss cried aloud to her husband, “and 210 million gallons of crude oil and 1.84 million gallons of dispersant out of the Gulf of Mexico, for the love of God, then what is it good for?”  Her husband took a deep breath. He said, “I hear you.” He added, “Let’s just get a new mattress for now. Let’s start there.”  It’s to Ms. Biss’s credit that she tells stories like this on herself in “On Immunity,” her new book exploring cultural myths about filth and purity and about the vaccinations we use to prevent disease. It’s a slim volume that weighs the scientific evidence and is strongly pro-vaccination (her son has all his shots), yet it’s one that has a grasp on the distrust that an increasing number of parents feel toward the medical establishment.  Moments like the mattress story above matter because “On Immunity” is a hothouse flower of a book, self-serious, heavy on the ponderosity. Yet what’s humid about Ms. Biss’s prose can overlap with what’s good about it. She presses down on the ways “our fears are dear to us,” and on how, when it comes to our health, “we are all irrational rationalists.”  “On Immunity” is Ms. Biss’s third book, after a volume of poetry, “The Balloonists” (2002), and a collection of essays, “Notes From No Man’s Land” (2009), which won a National Book Critics Circle Award.  In “On Immunity,” she is especially exacting on the topic of what she calls “people like me,” those blazingly hygienic parents, many of them upper-middle-class, for whom organized personal purity (air filters, water filters, “natural” foods) substitutes for organized religion.  She understands this impulse toward immaculateness. She also deplores it. She observes that purity is the “innocent concept behind a number of the most sinister social actions of the past century”: eugenics movements, forced sterilizations, miscegenation and sodomy laws, and the slaughter of millions. “Quite a bit of human solidarity has been sacrificed,” she says, “in pursuit of preserving some kind of imagined purity.”  Human solidarity is, in a way, her great subject in “On Immunity.” Our children need their shots not merely for their own sake, but also for the sake of others. “Immunity,” she declares, “is a public space.”  Statistics about immunization are increasingly alarming. There’s been a retreat from inoculation, often based on fears of autism promulgated by discredited doctors. The New York Times recently reported that while New York City schools over all have an immunization rate of around 97 percent, more than 37 of the city’s private schools have a rate below 70 percent.  Ms. Biss returns frequently to the notion of herd immunity, the idea that when enough people are vaccinated against a disease, it has trouble leaping from host to host. She drills into the selfishness and sanctimony of those parents who don’t vaccinate their kids.  “For some of the mothers I know, a refusal to vaccinate falls under a broader resistance to capitalism,” she writes. “But refusing immunity as a form of civil disobedience bears an unsettling resemblance to the very structure the Occupy movement seeks to disrupt — a privileged 1 percent are sheltered from risk while they draw resources from the other 99 percent.”  Ms. Biss tells the story of her own difficult pregnancy (she required a blood transfusion shortly after giving birth), and we learn about her son, who has severe allergies. The author combines her own experience with an overview of the history of vaccines, and with a great deal of thinking about immunology and its attendant metaphors.  Yet Ms. Biss is so given to finding metaphor wherever she turns that “On Immunity” can feel like climbing a mountain with someone who needs to stop along the way to examine the underside of every rock. The peak seems to recede into the distance.  Her prose, wonderfully dry at times, can be moist. “My father marveled at the natural world,” she writes, “far more often than he talked about the human body, but blood types were a subject on which he spoke with some passion.”  Her paragraphs can run themselves into ditches. The Food and Drug Administration and the Centers for Disease Control and Prevention oversee vaccine manufacture and testing. Yet Ms. Biss writes that “the presence of regulation resembles the absence of regulation in that neither is highly visible.” This is similarly true, of course, of gravity.  “On Immunity” casts a spell, however. There’s drama in watching this smart writer feel her way through this material. She’s a poet, an essayist and a class spy. She digs honestly into her own psyche and into those of “people like me,” and she reveals herself as believer and apostate, moth and flame.  Graywolf Press. 205 pages. $24.  A version of this review appears in print on October 1, 2014, on page C1 of the New York edition with the headline: A Needleful of Skepticism to Deliver Us. Order Reprints|Today's Paper|Subscribe
Eula Biss examines beliefs about filth and purity, from environmental toxins to vaccinations, in “On Immunity: An Inoculation.”