Injections after a dog scratch are ineffective within 72 hours at the latest. It is best to go to a regular hospital for a rabies vaccine injection within 24 hours. The sooner the better. If the vaccine is injected after this time, it will not be able to play its normal role. If a dog has rabies virus in its body, it is very likely to be infected. After being scratched or bitten by a dog, wash the wound with soap and water, and then go to the hospital for injection in time.