I'm sure the vampires will appreciate the increase in available blood; it might even have a better taste. Fruity and all.
Something tells me your blood tastes like athlete's foot.
If I recall correctly, self reporting has always been the standard way of checking this anyway, so you could already donate blood if that was of a higher moral priority to you than lying. I recall being rather taken aback when I discovered I couldn't donate as a bisexual.. then I realized I'd never had sex with a man anyway so I could just declare myself straight. Still, it felt degrading, so this gesture is positive.