Biss masterfully deconstructs the metaphor of the body as a fortress, often used to justify anxieties about vaccines. She argues that this simplistic view ignores the complex reality of our interconnectedness, where individual health is deeply intertwined with the health of the community. She delves into the historical evolution of this metaphor, drawing parallels with societal fears of contamination and invasion.

The decision to vaccinate often hinges on a profound act of trust—trust in scientific institutions, government agencies, and medical professionals. Biss eloquently articulates the difficulty of navigating this trust in an age of misinformation and readily available, often contradictory, information. She examines the historical reasons behind the erosion of trust in these institutions, particularly within marginalized communities who have often been subjected to medical exploitation.

At its core, "On Immunity" grapples with the ethical dilemmas surrounding vaccination. Biss acknowledges the anxieties associated with the minuscule risks posed by vaccines while simultaneously emphasizing the potentially devastating consequences of neglecting herd immunity. She compels readers to move beyond a purely individualistic understanding of risk and consider the broader societal implications of their choices.