POOR BABY and I would find a new vet ! they shouldn't have given him that many all at once and I don't even know WHY they gave you Corona ?? There's certain ones they should have but holy cow - not like that
I hate to say this but your vet misled you one what is necessary and what isn't and should never have done that to your little puppy
I really hope he's going to be ok - but I'd watch him very carefully all night -