With flu season around the corner in the United States and Europe, the push has begun once again to encourage people to receive their annual shots. But over the past few years, it9s become increasingly clear that the level of protection offered by the vaccine varies widely each flu season, from 10% to 60%. And new research has revealed surprising reasons for its lackluster performance. For decades, it appeared that the vaccine had an efficacy of 70% to 90%, but scientists now know that9s because they were using a misleading test—replaced in the 1990s—to assess whether it protected people. The traditional explanation for failure also has been revamped. The flu strains selected for the vaccine change each year based on what9s in circulation, and scientists long blamed failure on mutations that occur in the circulating viruses in the 6–8 months that pass between the vaccine being manufactured and used. But these "mismatches" sometimes occur in years when there9s solid protection, and some years with lots of failure have good matches. It turns out that other forces at work include mutations in the strain selected for the vaccine during the manufacturing process, which grows the virus in eggs. People9s prior exposure to influenza also can bias their immune system toward a response that undermines that vaccine-triggered immunity. And the vaccine strain selection process itself relies heavily on the ferret animal model, which can mislead, too. There9s an increasing call now to improve the vaccine and organize the research community to more collaboratively try to develop a "universal" flu shot that works against many strains and lasts for many years, if not a lifetime.

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为什么流感疫苗如此平庸？

随着美国和欧洲的流感季节即将来临，鼓励人们每年注射一次的运动再次开始。但在过去几年中，越来越清楚的是，疫苗提供的保护水平在每个流感季节都有很大差异，从 10% 到 60%。新的研究揭示了其表现不佳的令人惊讶的原因。几十年来，这种疫苗似乎有 70% 到 90% 的功效，但科学家们现在知道了这一点，因为他们使用了一种误导性的测试——在 1990 年代被取代——来评估它是否保护了人们。对失败的传统解释也进行了修改。为疫苗选择的流感毒株每年都会根据流通中的情况而变化，长期以来，科学家们将失败归咎于在疫苗制造和使用之间的 6-8 个月内，循环病毒中发生的突变。但是这些“错配”有时会出现在保护稳固的年份，而一些失败很多的年份却有很好的匹配。事实证明，其他起作用的力量包括在制造过程中为疫苗选择的菌株的突变，这使得病毒在鸡蛋中生长。人们之前接触过流感也会使他们的免疫系统偏向于破坏疫苗触发免疫的反应。而且疫苗株选择过程本身在很大程度上依赖于雪貂动物模型，这也可能会产生误导。现在越来越多的人呼吁改进疫苗并组织研究界以更加合作的方式开发“