Another small sample size for you: I know one family that's not vaccinated - both children are too young either way. Both parents and older child have caught it twice, about a year apart. Youngest is still nursing, and has not caught it. Dad and son are fine, but the Mom has an "annoying lingering cough" as she put it. But both times it wasn't worse than the flu for any of them, so in their case they see it as "we got lucky" but no one has any underlying conditions that would have caused complications.