Hi there,
You are not at a disadvantage unless you are a marginal candidate to begin with. The less-competitive you are, the earlier you should apply. That being said, I took the August MCAT, had my first interview in December and got into six out of the six medical schools that I applied to.
Rolling admissions is an advantage for you if you are a good candidate. This means that the class at medical schools is not filled and you have the same shot as someone who interviewed in September. Many schools that have huge numbers of applicants favor the rolling admissions because they can get the best candidates early or late.
Relax and plan on hitting your interviews with lots of enthusiasm. Nothing is as irresistable as a good candidate with lots of energy. If the class was full, you would not have been invited for an interview so put your best foot forward and give it your best shot.
As with this process, have an elaborate Plan B in case you do not get accepted. The more detailed and elaborate your Plan B, the more likely you are to be accepted to medical school. Besides, working on your Plan B keeps you sane at this date.
njbmd 🙂