On Immunity: An Inoculation was one of the two nonfiction books at this year’s BEA Editors’ Buzz. At just about 200 pages, including the notes and acknowledgements, it is undaunting in length, which I hope will encourage even more people to pick it up.

Disease is defined as “any deviation from or interruption of the normal structure or function of any body part, organ, or system that is manifested by a characteristic set of symptoms and signs and whose etiology, pathology, and prognosis may be known or unknown.” But an obsolete use of the word disease is “lack of ease; trouble,” more like today’s unease. And disease certainly does make people uncomfortable: the idea of it causes mental and emotional discomfort, while its physical effects can range from undetected to uncomfortable to fatal.

Eula Biss wades into this uneasy territory, and finds companions in other writers, historians, philosophers, anthropologists, and doctors. During the writing of On Immunity, Biss – already a published author and essayist – became a mother, and she approaches the topic of immunity and vaccination from a mother’s point of view as well as a “citizen thinker’s” perspective. She acknowledges that all parents’ decisions – to vaccinate or not to vaccinate their children – come from the same desire: to keep their children safe. But it is better to make these decisions from a place of knowledge than from a place of fear, and knowledge is what Biss strives for, and shares, in this book.

Fears of vaccines do not seem easily quieted by an abundance of expert risk-benefit analyses assuring us that the good they do is far greater than the harm.

One of the first steps in the process of deciding whether or not to vaccinate is risk assessment, and yet humans are not as good at this as we would like to think. Biss quotes the historian Michael Willrich, who says, “Perceptions of risk…can be stubbornly resistant to the evidence of experts.” People engage in dangerous activities (e.g. driving, riding in, or walking near cars) every day, but the familiarity we develop with these activities dulls our fear of the associated risks. “The disregard for statistical risk,” Biss writes, “may be at least partly due to an unwillingness to live lives dictated by danger.”

Risk perception may not be about quantifiable risk so much as it is about immeasurable fear….When we encounter information that contradicts our beliefs…we tend to doubt the information, not ourselves.

Safe and dangerous aren’t as binary as we’d like to think, either; as toxicologists say, “the dose makes the poison.” But, Biss notes, “most people prefer to think of substances as either safe or dangerous, regardless of the dose.” I caught myself in this exact thought pattern a single day after I finished reading On Immunity, while I was reading about the ingredients in a multivitamin; it’s difficult to remember, but any substance, even water, can be toxic in large enough doses, and small doses of “dangerous” substances may be harmless.

If vaccination is a choice people make at the individual level (“allowing oneself to remain vulnerable to disease remains a legal privilege today”), it is also a choice individuals are making on behalf of the larger community in which they live. The author’s father Roger Biss, a doctor, explains, “Vaccination works by enlisting a majority in the protection of a minority.” The more people who are vaccinated and carry immunity, the safer everyone is from disease. Achieving a 100% vaccination rate in any given population is unlikely, but by aiming for that rate, we have a better chance of attaining “herd immunity.” Unfortunately, Biss discovers, “We know the threshold [at which herd immunity is lost], in many cases, only after we’ve exceeded it.”

Faced with too much information, or misinformation, some people choose not to vaccinate, threatening the protection that herd immunity confers. Yet refusing to vaccinate “undermines a system…in which both the burdens and the benefits are shared across the entire population.” Or, as the author’s sister notes, “The health of our bodies always depends on choices other people are making.”

Biss includes a wealth of references, both in the text and in the notes; she draws upon such various sources as Susan Sontag, Bram Stoker (Dracula), Rachel Carson (Silent Spring), and Jean-Paul Sartre, among others. While I read On Immunity, however, I was often reminded of a book she didn’t mention: Leah Hager Cohen’s I don’t know: in praise of admitting ignorance and doubt (except when you shouldn’t). In this slim, wise volume, Cohen – also a mother, and also a Hampshire College graduate – explores the question, “How should we make decisions when we can’t know what’s right?”

We have to make the best decision we can, based on the best information we can gather. After a careful examination of research an opinion from many sources, Biss concludes, reasonably, that vaccination is the choice that is best for the individual, and for society at large – of which we are all a part. This works to everyone’s advantage; after all, “No single person…has the genetic material to respond to all diseases, but collectively humans have enough genetic diversity for humankind to survive any disease.”

I received a galley of this book from the publisher at BookExpo America 2014. Quotes in the review above are from the galley, and may differ from the final copy. On Immunity: An Inoculation will be published on September 30, 2014.