VFD meaning in Medical ?

The children's novel series A Series of Unfortunate Events features a large cast of characters created by Daniel Handler under the pen name of Lemony Snicket. The series follows the turbulent lives of the Baudelaire orphans after their parents, Bertrand and Beatrice, are killed in an arsonous structure fire and their multiple escapes from their murderous supposed distant relative Count Olaf, who is after their family fortune.

The author himself is also a character, playing a major role in the plot. Although the series is given no distinct location, other real people appear in the narrative, including the series' illustrator, Brett Helquist, and Daniel Handler himself.