Poly-Vi-Sol

My daughter is 5 days old. At her first pediatric appointment we were given a prescription for Poly-Vi-Sol as I am exclusively breastfeeding. I tried giving it to her tonight for the first time and she spit it all up 😢 I always listen to doctors but I’m wondering if this is really necessary. Have any of you used it with your babies? What are your thoughts/opinions on a multivitamin supplement if only breastfeeding?