We have given the shot at home for vomitting and have still ended up in hospital resulting in the trauma of the shot at home and the trauma of still ending up in hospital (especially when telling her that if she had the shot at home she wouldn’t have to go to hospital).    All children are different and all viruses are different.  We usually try oral dosing, double and triple, making sure it is not vomitted within an hour after giving it and keeping a close eye on her.  If meds are vomitted we usually give the shot or go to hospital.   We also give her "Hydralyte"  ice blocks as well which are oral electrolyte maintenance solution ice blocks, these work really well.  Good luck.