The Tuyen Quang Province General Hospital said the child was admitted last Sunday with fatigue and fear of water, wind and light and had vomited blood.
Doctors had diagnosed the boy with rabies.
But the same afternoon his condition became serious. His family asked to bring him home so he could die at home. He did later the same day.
His parents said their son was bitten by a neighbor's dog a month ago.
He had not been vaccinated against rabies.
"This is the reason why rabies victims die," a hospital spokesperson said, referring to the imperative need for vaccination.
There is no treatment for rabies. Once rabies sets in in an animal or human, the disease is 100% fatal. The most effective prevention is through annual vaccination of dogs and cats and vaccination for humans immediately after being bitten by a dog or cat (or scratched and bleeding).
When a child is bitten by a dog or cat, in the case of a small wound, wash it immediately with soap under a tap for 10-15 minutes, doctors said.
Otherwise, it is necessary to immediately take the child to the nearest medical facility for emergency treatment.
Doctors recommend that parents limit their children's contact with pets, especially unknown dogs and cats.
Families with dogs or cats must have them properly vaccinated.