The best time to receive the flu vaccine is in late September and early October each year for any healthy person who may be infected with the influenza virus. Since the high season for influenza is winter, i.e. November, and it takes about 15 days for protective antibodies to develop after influenza vaccination, it is recommended to start vaccination about one month before the peak of the influenza epidemic in order for the vaccine to have an effective protective effect. Usually, vaccination before an influenza epidemic has a 60-90% protective effect, but antibodies to the influenza virus can only be maintained for about one year, and the epidemic strain of the influenza virus changes every year, so the vaccine is developed for the epidemic strain of that year. Even if the epidemic strain does not mutate, it is still necessary to receive influenza vaccine, and immunity can only be obtained continuously by annual vaccination. Adverse reactions after vaccination are rare and may cause pain, redness, swelling, itching, or fever or rash at the vaccination site, which will subside on its own in about 3 days without special treatment. Influenza vaccination does not produce dependence, and it is recommended that people in areas with a high incidence of influenza, as well as high-risk groups such as children, the elderly, patients with chronic diseases, medical personnel, and pregnant women, need to receive influenza vaccination to prevent influenza.