Conflicting reports have emerged about the effectiveness of the live attenuated influenza vaccine. The live attenuated influenza vaccine appears to protect particularly poorly against currently circulating H1N1 viruses that are derived from the 2009 pandemic H1N1 viruses. During the 2015-16 influenza season, when pandemic H1N1 was the predominant virus, studies from the USA reported a complete lack of effectiveness of the live vaccine in children. This finding led to a crucial decision in the USA to recommend that the live vaccine not be used in 2016-17 and to switch to the inactivated influenza vaccine. Other countries, including the UK, Canada, and Finland, however, have continued to recommend the use of the live vaccine. This policy divergence and uncertainty has far reaching implications for the entire global community, given the importance of the production capabilities of the live attenuated influenza vaccine for pandemic preparedness. In this Personal View, we discuss possible explanations for the observed reduced effectiveness of the live attenuated influenza vaccine and highlight the underpinning scientific questions. Further research to understand the reasons for these observations is essential to enable informed public health policy and commercial decisions about vaccine production and development in coming years.

中文翻译：

---

实施减毒活流感疫苗的紧迫挑战。

关于减毒活流感疫苗的有效性的矛盾报道已经出现。减毒活流感疫苗似乎对目前正在流行的源自2009年大流行H1N1病毒的H1N1病毒的保护作用特别差。在2015-16流感季节，大流行H1N1是主要病毒，美国的研究报告称，活疫苗对儿童完全没有疗效。这一发现导致美国做出了一项至关重要的决定，建议在2016-17年度不要使用活疫苗，并改用灭活的流感疫苗。但是，包括英国，加拿大和芬兰在内的其他国家仍建议使用活疫苗。这种政策分歧和不确定性对整个全球社会都有深远的影响，考虑到减毒活流感疫苗的生产能力对于大流行防范的重要性。在此个人观点中，我们讨论了观察到的减毒活流感疫苗有效性降低的可能解释，并强调了基础科学问题。进一步研究以了解这些观察的原因，对于在未来几年中就疫苗生产和开发做出知情的公共卫生政策和商业决策至关重要。