There is no clinical evidence to prove that taking cold medicine the day before has any effect on vaccination. Cold medicine usually does not have any effect on the effectiveness of the vaccine, and if you do not feel any discomfort, you can continue vaccination after taking cold medicine by mistake; however, if you take cold medicine because of cold symptoms, vaccination is not recommended, because cold may have some effect on the effectiveness of the vaccine or increase the incidence of adverse reactions. Therefore, vaccination during a cold is generally not recommended. The vaccine enters the body and stimulates the immune system to produce an immune response, which has a certain immune effect. When the human body has a cold, there may be some pathogens infecting the body and the immune system is fighting against the virus that causes the cold. Some people may also have some adverse reactions after vaccination, such as fever, cough, diarrhea, etc. These symptoms are very similar to those of a cold. If these symptoms appear after vaccination, it is difficult to determine whether the symptoms are caused by a cold or an adverse reaction occurs after vaccination, which may affect the doctor’s judgment and subsequently prevent him/her from giving the patient the correct treatment measures and delay the condition. Therefore, in the case that the human body suffers from a cold and has taken cold medicine the day before the vaccination, it is not recommended to continue the vaccination, and the vaccination can be postponed until the cold has fully recovered so that the vaccine will not play a better protective role or aggravate the condition of the cold. However, in the case of extremely urgent and important vaccines such as rabies vaccine, the vaccine can be given after the cold and cold medicine.