Hello, my name is***** and I have over 20 years of experience as a veterinarian. I am sorry to hear that Jumbles is vomiting yellow material.
Yellow in the vomit means that the small intestine is refluxing bile into the stomach so that when he vomits you see the yellow color.
That isn't normal as bile doesn't belong in the stomach, and it does mean that there is some reverse motility, but it isn't specific for any particular disease process.
In his case I don't think this is a direct result of his vaccines, as if that were the case I would have expected him to vomit on Thursday or Friday, not today. However if he tends toward a sensitive stomach then the stress of a veterinary visit and his immune system responding to vaccines could have lead to increased stomach acid production and an upset gastrointestinal tract. We see this in dogs with inflammatory bowel disease.
In that case these dogs may seem to vomit more on an empty stomach so fin the future feeding him small meals several times a day, and maybe a snack before bedtime, may be very helpful. It may also be helpful to put him on an acid reducing medication as too much stomach acid, especially on an empty stomach, is very irritating and predisposes to vomiting.
Or it may be that his vomiting is unrelated to the vaccines/veterinary visit. In many cases vomiting is triggered by eating something they should not, too much table food, too many treats or something they find outdoors.
More serious causes of vomiting include viral or bacterial infections, chronic pancreatitis, esophageal reflux, a dietary allergy or sensitivity, inflammatory bowel disease, internal organ failure (kidney or liver disease), a full or partial gastrointestinal obstruction or even infiltrative cancers such as lymphoma.
At this point you can give acid reducers to try and settle his stomach and feed him a bland diet for a few days. If he seems to vomit most in the morning on an empty stomach I recommend giving him an acid reducer medication dose before bed so that it is in his system in the morning. You can give either:
1) Pepcid ac (famotidine) at a dose of ¼ of a 10mg tablet per 5 to 10 pounds of body weight every 12 hours
2) Prilosec (omeprazole) at a dose of ¼ of a 10mg tablet per 5 to 10 pounds of body weight every 24 hours
These are both acid reducers and should help him feel better. They are quite safe and can be used long term if necessary.
I would pick up all food for now and water for a couple hours to allow the acid reducer a chance to work and his stomach to settle after the acid reducer is given.
In a couple hours when you give water make sure it is in small amounts only. If he drinks too much too quickly that can lead to vomiting. To get some electrolytes in you can also offer her a 50:50 mix of pedialyte and water.
If there is no vomiting for 6-8 hours offer a bland diet of 1/3 boiled, minced, white, skinless chicken or boiled, lean hamburger and 2/3 boiled, plain, white rice mixed with some low salt chicken or beef broth to make it more palatable and easy to lap up and swallow. If he refuses that you can offer a little meat baby food. If he refuses both then don't push it.
But if things go well and he does eat and doesn't vomit feed him the bland diet for 2 to 3 days then slowly start to mix back in his regular food, a little more at each meal. It should take about 5 to 7 days to slowly convert him back to a regular diet.
If he continues to vomit even with the acid reducers, runs a fever (more than 103F rectally), has a tense painful belly or if he refuses to eat he should see a veterinarian for an examination, diagnostics, injectable anti-nausea drugs intravenous fluids and supportive care.
Please let me know if you have other details or a particular question based upon my response.