Influenza vaccines are mainly produced to prevent epidemic influenza and are currently available in three main types: Type A, B, and C. The target population for influenza vaccine administration primarily includes the elderly, preschool children, and patients with chronic underlying diseases, who are more suitable for vaccination. For children under three years old, the influenza vaccine should be administered twice, as it is administered via muscle injection and cannot be used intravenously. For this age group, the two doses should be spaced at least four weeks apart. For children over three years old and adults, an annual vaccination is sufficient. The optimal time for influenza vaccination is usually in September and October, as influenza tends to outbreak in winter and spring, so vaccinating during these months can greatly prevent influenza.