It’s been six months since the dog bite and now the vaccine is not useful for post-exposure prophylaxis (the timely use of medication to prevent infection after a high-risk behavior that could have been infected with the virus), but it is still useful for pre-exposure prophylaxis (the use of a specific medication to prevent infection after a behavior that predisposes to infection before the virus was contracted). Often a dog bite may carry a risk of rabies, and the patient needs to be vaccinated against rabies within 24 hours of the bite, thus providing post-exposure prophylaxis. While rabies generally has an incubation period of 1 to 3 months, only a very small percentage of patients may have an incubation period of less than 1 week or more than 1 year. Therefore, the patient has been bitten by a dog for six months now vaccination is not useful for post-exposure prophylaxis. However, most patients who have been bitten by a dog for six months and still do not show symptoms of rabies are safer and generally not life-threatening. And patients vaccinated now still have better results for pre-exposure prophylaxis, and antibodies can be maintained in the body for at least six months. If the rabies vaccine is used for pre-exposure prophylaxis, the patient will need to receive a booster injection 1 year later, and subsequently receive another booster injection every 1~3 years. It is recommended that patients receive rabies vaccination in a timely manner after being bitten by a dog, and the earlier the vaccination is administered, the better the preventive effect.