Well, I can hardly talk about the changing idea of vampires without touching on werewolves as well. I mean, there are in the top three monsters of all time. Also, they spend a lot of time being the main enemy of vampires so I feel like, in order to not pick a side I have to cover both.
Ancient Lore/Classic Fiction:
Werewolves have also been known to be called Lycans, which comes from the word lycanthropy, which is the term used for the condition of being a werewolf. The word lycanthropy speaks to both the ability to transform yourself into a wolf and the actual act of transforming. In the classic terms of the condition it is something to be feared and it’s a curse, not a gift. In ancient lore and classic fiction it is something the person does not have control over and is, more often than not, a very painful process that is forced upon a person on the night of the full moon. Once one takes the form of the wolf man (s)he has no control over what they do. They do not remember the person they were before the transformation and would likely kill their best friend or lover without a second thought in wolf person form. There are some bits that change, such as lycanthropy being passed down genetically. There have been both examples of this being the case and this not being the case.
Physically the werewolf can be distinguished from a normal wolf by size. Lore once again changes a bit based on what you are reading from here. There is lore stating that they look no different from normal wolves except that they are far too large to be a normal wolf. Then there are accounts of werewolves standing on their hind legs and being less hairy than normal wolves, as well as larger.
Most recently there have been both book and movie representations of wolf men/women that have changed the way we look at the werewolf. While the basic appearance is the same, giant wolf-like creatures who are very animalistic in nature, there has been a push towards werewolves who are aware of what they are doing when they are in wolf form, or are even making conscience decisions about their actions. There has also been a push towards werewolves that have control over their changes (I am NOT talking about Twilight, those are shape shifters, it’s even stated as such in those crappy books), and do so with apparently less pain than those who cannot. One of the few things that seems to not change, however, is the need for a moon or for it at least to be night when the change occurs.
The idea of a werewolf who is conscience of their actions actually, in my opinion, makes for a scarier villain as they could always claim to be out of control and yet have full control of their actions. However, a werewolf who has no control makes for a more sympathetic character. More than anything, I’d love to see a moment when the werewolf with control meets of one who lacks it, i feel this dynamic could be quite exciting to watch.