Why don't vets use the Parvo serum on Parvo puppies?

Sometimes the virus is just too far along :/ Sorry about your pup. But i've never once heard talk of this serum and I have worked at a vet clinic for 7 years!! Sometimes there are some bogus things out on the market! But I will have to look into that one! We always have good comeback from the parvo virus with the normal IV fliuds w/ B12 & Bcomplex & and antibiotic Cefazolin injectable added to the fluid bag and they stay hospitalized up to a week or longer depending on the severity. But a lot of it depends on how long the owner waited after symptoms occur. It only takes about 3 days for a pet to die from parvo after the symptoms of V/D & not eating occur. They basically die of dehydration. So the IV fluids keep hydrated until the virus can pass, there is no cure, just supportive therapy. Hope that gives a little info! Sorry about your pup .