How soon should I expect my dog to start responding to Parvo treatments?

I have a 2 year old Shar Pei that has never been vaccinated for Parvo. I know he should have been and I'm kicking myself in the butt for that. Two Saturday's ago, I was at a friends house who has a new puppy about 13 weeks old. At the time we didn't know her pup had parvo and I guess I brought it into my yard. That following Wednesday, my dog starting acting very depressed and not eating. At first, I assumed it was because my husband was out of town. By Thursday night knew something was wrong w/ him so Friday morning I took him to the vet. They said he had parvo. He hadn't been throwing up or had diahrrea. I opted to take him home with the medicines and tried to give him pedialyte. By Firday night he was throwing up everything, every 1 to 2 hours. I kept giving him the Pedialyte knowing he would just throw it up but something is better than nothing right? He has been on IV's since Saturday morning and since then has only thrown up once. However, today (his 3rd day) he has had bad diahrrea. The vet told me he had done it like 2 or 3 times I believe. How soon should I expect to see some improvement or is that improvement? I know the objective is to keep him from throwing up and pooping himself but today is the first day since Wed. that he has to my knowledge. I'm so ready for my baby to come home and I have definitely learned my leason on being cheap. I have sprayed my house and yard as much as possible w/ bleach solution. Can he catch it again after having it and being vaccinated?