In Sam Harris’s blog he writes
Most of us have been around this block often enough to know that many
“former atheists”—like Francis Collins—spent so long on the brink of
faith, and yearned for its emotional consolations with such vampiric
intensity, that the slightest breeze would send them spinning into the
I pride myself in usually being able to understand Mr Harris’s writings, but the word “vampiric” was new to me (indeed, the spell checker underscores it in red here on english.SE). Looking it up in a dictionary, it is defined (naturally enough) as “pertaining to vampires.”
But that hardly helps give it meaning to me in the present context.
It’s an extra emphasis on “intensity”. Vampires are, after all, intense individuals.
I doubt you’ll find a definition of “vampiric” anywhere that includes this; it’s certainly an artistic flourish. It is augmented by the other-worldliness overlap that religious faith and the supernatural share.