Importance During the 2023-2024 respiratory syncytial virus (RSV) season in the United States, 2 new RSV prevention products were recommended to protect infants in their first RSV season: nirsevimab and Pfizer's maternal RSV vaccine. Postlicensure studies are needed to assess prevention product impact and effectiveness. Objective To compare the epidemiology and disease burden of medically attended RSV-associated acute respiratory illness (ARI) among children younger than 5 years during the 2023-2024 RSV season with 3 prepandemic RSV seasons (2017-2020), estimate nirsevimab effectiveness against medically attended RSV-associated ARI, and compare nirsevimab binding site mutations among circulating RSV in infants with and without nirsevimab receipt. Design, Setting, and Participants This study included a prospective population-based surveillance for medically attended ARI with systematic molecular testing for RSV and whole-genome sequencing of RSV positive samples, as well as a test-negative case-control design to estimate nirsevimab effectiveness. The study was conducted in 7 academic pediatric medical centers in the United States with data from RSV seasons (September 1 through April 30) in 2017 through 2024. Participants were children younger than 5 years with medically attended ARI. Exposure For the nirsevimab effectiveness analyses, nirsevimab receipt among infants younger than 8 months as of or born after October 1, 2023. Main Outcome and Measure Medically attended RSV-associated ARI. Results Overall, 28 689 children younger than 5 years with medically attended ARI were enrolled, including 9536 during September 1, 2023, through April 30, 2024, and 19 153 during the same calendar period of 2017-2020. Of these children, 16 196 (57%) were male, and 12 444 (43.4) were female; the median (IQR) age was 15 (6-29) months. During 2023-2024, the proportion of children with RSV was 23% (2199/9490) among all medically attended episodes, similar to 2017-2020. RSV-associated hospitalization rates in 2023-2024 were similar to average 2017-2020 seasonal rates with 5.0 (95% CI, 4.6-5.3) per 1000 among children younger than 5 years; the highest rates were among children aged 0 to 2 months (26.6; 95% CI, 23.0-30.2). Low maternal RSV vaccine uptake precluded assessment of effectiveness. Overall, 10 of 765 case patients (1%) who were RSV positive and 126 of 851 control patients (15%) who were RSV negative received nirsevimab. Nirsevimab effectiveness was 89% (95% CI, 79%-94%) against medically attended RSV-associated ARI and 93% (95% CI, 82%-97%) against RSV-associated hospitalization. Among 229 sequenced specimens, there were no differences in nirsevimab binding site mutations by infant nirsevimab receipt status. Conclusions and Relevance This analysis documented the continued high burden of medically attended RSV-associated ARI among young children in the US. There is a potential for substantial public health impact with increased and equitable prevention product coverage in future seasons.

中文翻译：

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2023-2024 年幼儿呼吸道合胞病毒病负担和 Nirsevimab 有效性。


重要性 在美国 2023-2024 年呼吸道合胞病毒 （RSV） 季节期间，推荐了 2 种新的 RSV 预防产品来保护处于第一个 RSV 季节的婴儿：nirsevimab 和辉瑞的母体 RSV 疫苗。需要进行许可后研究来评估预防产品的影响和有效性。目的 比较 2023-2024 年 RSV 季节与 3 个大流行前 RSV 季节 （2017-2020） 期间 5 岁以下儿童就医 RSV 相关急性呼吸系统疾病 （ARI） 的流行病学和疾病负担，估计 nirsevimab 对就医 RSV 相关 ARI 的有效性，并比较接受和未接受 nirsevimab 治疗的婴儿循环 RSV 中 nirsevimab 结合位点突变。设计、设置和参与者 本研究包括对就医 ARI 的基于人群的前瞻性监测，对 RSV 进行系统的分子检测和 RSV 阳性样本的全基因组测序，以及测试阴性病例对照设计以估计 nirsevimab 的有效性。该研究在美国的 7 个学术儿科医疗中心进行，数据来自 2017 年至 2024 年的 RSV 季节（9 月 1 日至 4 月 30 日）。参与者是 5 岁以下患有就医 ARI 的儿童。暴露 对于 nirsevimab 有效性分析，截至 2023 年 10 月 1 日或之后出生的 8 个月以下婴儿接受 nirsevimab。主要结果和测量 医学参与的 RSV 相关 ARI。结果 总体而言，共纳入 28 689 名 5 岁以下就医 ARI 儿童，包括 2023 年 9 月 1 日至 2024 年 4 月 30 日期间的 9536 名，以及 2017-2020 年同期的 19 153 名。在这些儿童中，16 196 名 （57%） 是男性，12 444 名 （43.4） 是女性;中位 （IQR） 年龄为 15 （6-29） 个月。在 2023-2024 年期间，在所有就医发作中，RSV 儿童的比例为 23% （2199/9490），与 2017-2020 年相似。2023-2024 年 RSV 相关住院率与 2017-2020 年季节性平均住院率相似，5 岁以下儿童每 1000 人中有 5.0 人（95% CI，4.6-5.3）;0 至 2 月龄儿童的发生率最高 （26.6;95% CI，23.0-30.2）。母体 RSV 疫苗接种率低排除了有效性评估。总体而言，765 名 RSV 阳性患者中有 10 名 （1%） 和 851 名 RSV 阴性对照患者中有 126 名 （15%） 接受了 nirsevimab。Nirsevimab 对就医 RSV 相关 ARI 的有效性为 89% （95% CI，79%-94%），对 RSV 相关住院的有效性为 93% （95% CI，82%-97%）。在 229 个测序标本中，婴儿 nirsevimab 接收状态对 nirsevimab 结合位点突变没有差异。结论和相关性 该分析记录了美国幼儿就医 RSV 相关 ARI 的负担持续很高。在未来季节增加和公平的预防商品覆盖率可能会对公共卫生产生重大影响。