This Bill Gates recommended-book explores immunity from a philosophical point of view.
There are a lot of great points in the book. For instance, immunity is often community-based rather than individual-based: someone who is not vaccinated but who lives among those who are is better protected than someone who is vaccinated but lives among those who aren't. The book is also very educational from a historical perspective, as the reader learns a lot about how inoculations and other medical practices were originated and have evolved over time.
What I didn't like was that there was a lot of rambling, in my opinion. Biss offers a great deal of anecdotes and stories about her own experiences (mostly as a mother of a sick child) which I didn't care much for. Biss also talks about how study results are mostly not reproducible (agreed!) but then goes on to cite myriad one-off studies to make her points!
On Immunity is an interesting book but is not one I'd particularly recommend.