Replaced a gable vent, Will it leak without caulking?

Squirrels ate through my wooden gable vent and got into my attic. I replaced it with the same exact gable vent, bought from home depot. Left the flashing at the from the old one. However after It was installed with 16d finish nails i realized i forgot to put caulking around the flange. Is this going to cause a terrible leak? I plan this fix to be semi temporary and want to replace the vent once again within a year or two when I re-side the whole house. Any input would be appreciated.