The two main characters of The End of Men meet on p. 261!
Catherine: “Do you think it will happen again?”
Amanda: “Just because your husband left you doesn’t mean your house can’t catch on fire. In other words, tragedy doesn’t immunize you against further tragedy . . . The vaccine we have should be effective, yes, and we can use it to adjust to new strains. But in theory the Plague could mutate, allowing the vaccine to be ineffective.”