Influenza vaccination has side effects such as drug allergy, systemic adverse reaction and infection. 1. Drug allergy: the sensitizing components in the influenza vaccine can trigger patients with metabolic inflammation, inflammatory cell activation and release of inflammatory mediators, making vasodilatation and increased vascular permeability, which can cause local or systemic rashes, itching and other allergic symptoms, and the more serious ones may have respiratory distress and shock, which is forbidden to re-vaccinate this vaccine. 2. Systemic adverse reactions: Influenza vaccine stimulates the body to produce the corresponding antigen-antibody reaction through influenza antigen. Therefore, after the flu vaccine, there may be adverse reactions, including runny nose, nasal congestion, headache, fever, abdominal pain, myalgia and so on. 3. Infection: If the local wound is not properly cared for after the flu shot, it may lead to bacterial or viral infection, resulting in local inflammation, leading to redness, swelling, pain and other symptoms in and around the eye of the needle. Influenza vaccine is contraindicated for people who are allergic to any of the components of the vaccine, patients who have recently developed fever, and patients who are suffering from an exacerbation of an underlying disease. It is important to follow your doctor’s advice when receiving the flu vaccine, and to seek medical attention if you experience any discomfort after vaccination.