What's startling is that the invented elements have been done so well. (One tolerable, perhaps inevitable, exception is a moist, uplifting coda.) Without giving any plot points away, I can tell you that a climactic scene turns on a marvelous surprise, and promise you frequent spasms of suspense that will grow almost unbearable.
Withoutexception, of the vaccines given to their children over the first 15 months of life, the one they felt most comfortable with was the oral polio vaccine.