病毒不断变异，接种疫苗有效吗？专家回应：流感疫苗组分每年更新，匹配当季流行株

Core Viewpoint - The matching of influenza vaccines, particularly for the H3N2 subtype, has improved significantly compared to previous years, with over 95% similarity to circulating strains, addressing public concerns about vaccine effectiveness against evolving viruses [1][2]. Group 1: Vaccine Effectiveness - The influenza vaccine is updated annually to match the circulating strains, ensuring better protection for the current flu season [1][2]. - Antibody levels from the flu vaccine typically decline after 6-8 months, necessitating annual vaccination to maintain effective immunity [2][3]. - The current flu season shows a predominance of the H3N2 subtype, accounting for over 95% of cases, with some H1N1 and B subtype activity noted [2][3]. Group 2: Public Health Recommendations - Individuals who have previously contracted influenza should still receive the vaccine, as different subtypes can circulate simultaneously, and immunity to one does not confer protection against others [3]. - The winter-spring period is identified as a peak time for influenza and other respiratory infections, prompting health authorities to encourage vaccination among high-risk groups [3].