What are the reaction symptoms after receiving the quadrivalent influenza vaccine?

After receiving the quadrivalent influenza vaccine, possible reaction symptoms mainly include: 1. Local reactions: Pain, redness, swelling, hard lumps, or itching at the injection site may occur, and these symptoms usually resolve on their own within a few days. 2. Systemic reactions: Some individuals may experience systemic symptoms such as fever, headache, fatigue, and muscle aches. These symptoms are generally mild and short-lived. 3. Other reactions: A small number of people may develop more severe reactions, such as high fever, difficulty breathing, hoarseness, hives, weakness, or rapid heartbeat. It is recommended to remain under observation for 30 minutes after vaccination to promptly manage any potential adverse reactions. If any of these symptoms occur, seek medical attention immediately.