Influenza can be transmitted repeatedly, even after vaccination. Influenza is an acute infection of the upper respiratory tract caused by the influenza virus and is a contagious disease. Influenza is often triggered by factors such as staying up late, getting wet, getting cold, fatigue, and alcohol abuse. When suffering from influenza and the body is in a state of lowered resistance, it is possible to be re-infected when exposed to the influenza virus again. If the body is vaccinated against influenza, there is still a probability that the body will be infected again and again and can be infected with other types of influenza viruses. This is because the flu vaccine does not protect against all viruses, but only against some of the influenza viruses.