I doubt you would be giving your infant vitamins w/o talking to your pedi already so I am guessing you are asking because your 2 month old is spitting out the vitamins. If so, we had this same problem. Our daughter wouldn't even drink them in a bottle mixed with breastmilk (we never tried formula). What I would do was put the vitamins in a bottle nipple...start feeding her when she was hungry, pull her off after a minute, give her the vitamins in the nipple, and then put her right back on (breast or bottle) before she realized what was happening. It didn't work every time but eventually she got used to the taste of the vitamins and it got better. By the time she was 9 months she had no problem drinking the vitamins straight out of the dropper!
Good luck!