Only male vampires have shapeshifting abilities, but there's a distinct drawback . . . after a couple of centuries they end up looking like mummified monkeys, like this guy (Athanasius Kircher).

What's happening is this: the "real" vampire is a parasitic organism that replaces the human host's inner organs, and doesn't merely hijack the bones, nerves and muscles but transforms them to better suit its needs via lateral gene transfer. In female vampires this means subtle changes like the growth of fangs and venom sacks, but male vampires also gain the ability to rapidly reshape their bodily structure into a unique 'combat morph". This is part of their reproductive strategy, as male vampires fight each other viciously in order to control harems of females. Unfortunately for them, the parasite organism capitalizes on this somatic plasticity to continue 'refining' them, for example the mandible atrophies into a simple bone splint because they no longer need to bite down strongly, and the eyes become huge - the better to see in the dark with.

Quick note - male and female refer to the parasite organism only. It's perfectly possible for a male human host to be carrying a female parasite, and vice versa. The parasite effectively neuters the host, so the human's original gender is unimportant.

http://www.furaffinity.net/view/1294143/ Is a transformed male vampire in his prime.

http://www.furaffinity.net/view/1305629/ Is a view of the parasite itself.