Reading the spell, I see no reason the spell ends after that initial save. That's only to see if the creature is frightened or not. Is the creature frightened of the scary spell dealing damage to it? No? Well, it's still taking damage!
The 3E spell worked in the fashion where the Will save negated the entire spell, then the second save was death or cake. I mean damage. This doesn't read that way.
Cheers!
This is what the spell appears to do.
As a community, we are used to spells ending if a save is made, but nothing in the text indicates that the first save ends the spell.