Influenza A H3N2 is a recurrent infection that is possible. Influenza A H3N2 is a respiratory infection caused by a mucovirus. Patients usually have symptoms such as high fever, headache, fatigue, general body aches and pains, and sometimes diarrhea and vomiting. Patients with more serious illnesses may develop pneumonia and respiratory failure, which may even lead to death. After a patient has had influenza, the body will produce a certain titer of protective antibody, but this antibody cannot exist for a long time, and the level of antibody titer will decrease with the prolongation of time. Therefore, it is still possible for patients to be infected with influenza A (H3N2) repeatedly. It is recommended that susceptible people such as the elderly and children should be vaccinated as much as possible for prevention.