I would think you’d have a shot, but it is very competitive. As usual, if you get that far the standard advice would be to have a very robust list of RD applications as well.
Just to give you an idea, a couple years ago Vanderbilt reported an overall ED(1+2) of 17.6%, and an ED2 rate of 10.3%. Last year I don’t believe they reported both, but the ED(1+2) rate was 15.2%. So I think it is a good bet the ED2 rate was significantly down into single digits.
The ED admitted student profile was also extremely competitive. Like the middle 50% ACT was 34-35, which is the same as their reported enrolled middle 50% in their 2023-24 CDS. 96% of the ED admitted students were in the top 10th of their HS class, which is actually higher than their CDS-reported 92.5%.
So really no sign of a significant ED “boost”, at least when it comes to academics. We of course don’t know about other unreported qualifications, but I really think unhooked applicants need to understand that applying ED at colleges like this is extremely unlikely to take a candidate who was not quite what they were looking for and turn them into an admit.
But again, Vandy could in fact want you, even if Duke defers you. I would just have very modest expectations for how much ED2 would actually help convince Vandy to want you. You are really need to going to do that based on your actual application.