4 month old puppy is sick

My 4 month old Lab/Husky stopped eating and drinking water late today and is not playful. She also has thrown up what looks like white mucus. Her nose is warm and dry and her fur looks dull. I have not been able to get her shots just yet, I have been waiting to get a day off work. Please let me know what the issue may be and if it is something that may be very serious

[Aleda M Cheng, D.V.M., C.V.A]

It is really best for you to take her to the vet ASAP.  

An unvaccinated dog can succumb to Parvovirus,  for instance.  Parvo vaccine is one of the important vaccines usually given to puppies beginning at 6 to 8 weeks of age.  Parvo disease can be deadly in puppies.   Parvovirus has become more and more common in the environment, unfortunately.

But what ever the reason, a puppy of any breed who will not eat can get hypoglycemia, which can be very debilitating.