Finally, a good question! Well, let's see...vampires are destroyed by sunlight, right? So, the sun is powered by nuclear fusion, and that's when you join hydrogen atoms together to get helium.
Crow T. Robot
Therefore, a Hydrogen bomb would kill a vampire, owing to its fusion-based energies. But a standard "A-bomb" would not as it's powered by a fission reaction.
Crow T. Robot
It's simple, once you use logical thinking, and science!