when I reapplied this year I had about half and half new and old letters. I used the same committee letter and a few of the letters from last year that I knew were really good but also added some new ones from doctors I had shadowed with since last year's cycle and one from a professor I had during my last semester in college that really liked me and was excited about writing an LOR for me so I figured it would be pretty good.
It worked for me... accepted second time around! Don't lose hope... re-applying kinda sucks but the second time around is much easier since you know what you're getting in to! Good Luck!