Hmm.. only four days. Does it look oily to you or opaque and whitish..?
Most infections I have seen that were definitely infections the plaques grew, started creating tendrils, and bubbles and were opaque looking.
Non-infections that were "contaminated" with coffee & Chocolate oils, Vanilla bean stuff, etc.. had a more of an oily composition.. and didn't grow to much more than a thin film or junk.
To me it looks like it COULD simply be just the vodka and vanilla beans..
As I mentioned there are much better experts at this than me.. I haven't had one yet. But did a lot of research on it when I thought my batches were infected and have seen other friends that brew get them.
Seems your options are:
Keep an eye on it and see if it grows, and if it starts growing bubbles
(Prove its an infection)
Let it ride
(Its beer.. and beer is good.. what it becomes it becomes.. )
Bottle it now and let condition in bottles..
(In case it is infection and you can get some beer out now before the infection gets through out the beer)
Rerack it into a fresh sanitary secondary, without additions.. and lose the last inch or so.. and see what happens..
If it were me.. I would probably let it ride and see what happens. If it gets too ugly then worry, otherwise it may just be those Vanilla beans and its no big deal.
Often I hear, its best to not look at it.. just let it do its thing, and when bottling time comes you get what you get. 99 times out of 100 it comes out fine.