Will a blood transfusion help my 14 week old Neo. Mastiff survive Parvo?

This past friday, my husband and I purchased a 14 week old female Neo. Mastiff. That same evening we took her to the vet to get her second set of vaccs. The next morning, I noticed she was uninterested in food and water, and she began to vomit. I immediately took her to the vet where she was tested for parvo, and it came up positive. They began IV treatment right away. She has been there for 4 day's now. This morning she was very depressed. The vet recommended doing blood work to check her WBC and they came back low (1000) so, at 11:45 this morning they began a blood transfusion. I called and they said it will take 5 hours to complete. Will this blood transfusion significantly raise her survival rate? Does anyone have any experience with this?