Background Adult studies have demonstrated within-season declines in influenza vaccine effectiveness (VE); data in children are limited. Methods We conducted a prospective, test-negative study of children 6 months–17 years hospitalized with acute respiratory illness at 7 pediatric medical centers during the 2015-2016 through 2019-2020 influenza seasons. Case-patients were children with an influenza-positive molecular test matched by illness onset to influenza-negative control-patients. We estimated VE [100% x (1 – odds ratio)] by comparing the odds of receipt of ≥1 dose of influenza vaccine ≥14 days before illness onset among influenza-positive children to influenza-negative children. Changes in VE over time between vaccination date and illness onset date were estimated using multivariable logistic regression. Results Of 8,430 children, 4,653 (55%) received ≥1 dose of influenza vaccine. On average, 48% were vaccinated through October and 85% through December each season. Influenza vaccine receipt was lower in case-patients than control-patients (39% vs. 57%, p < 0.001); overall VE against hospitalization was 53% (95% CI: 46%-60%). Pooling data across 5 seasons, the odds of influenza-associated hospitalization increased 4.2% (-3.2%-12.2%) per month since vaccination, with an average VE decrease of 1.9% per month (n = 4,000, p = 0.275). Odds of hospitalization increased 2.9% (95% CI: -5.4%-11.8%) and 9.6% (95% CI: -7.0%-29.1%) per month in children ≤8 years (n = 3,084) and 9-17 years (n = 916), respectively. These findings were not statistically significant. Conclusions We observed minimal, not statistically significant within-season declines in VE. Vaccination following current ACIP guidelines for timing of vaccine receipt remains the best strategy for preventing influenza-associated hospitalizations in children.

中文翻译：

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季节性疫苗对儿童流感相关住院治疗的持续有效性：来自 2015-2016 年至 2019-2020 年新疫苗监测网络的证据


背景 成人研究表明流感疫苗有效性 (VE) 在季节内下降；儿童数据有限。方法 我们对 2015-2016 年至 2019-2020 年流感季节期间在 7 个儿科医疗中心因急性呼吸道疾病住院的 6 个月至 17 岁儿童进行了一项前瞻性、测试阴性的研究。病例患者是流感分子检测呈阳性的儿童，其发病情况与流感阴性对照患者相匹配。我们通过比较流感阳性儿童和流感阴性儿童在发病前 ≥14 天接受 ≥1 剂流感疫苗的几率来估计 VE [100% x（1 – 优势比）]。使用多变量逻辑回归估计疫苗接种日期和发病日期之间 VE 随时间的变化。结果 8,430 名儿童中，4,653 名（55%）接受了 ≥1 剂流感疫苗。平均而言，每个季节 10 月和 12 月期间分别有 48% 和 85% 的人接种了疫苗。病例患者的流感疫苗接种率低于对照患者（39% vs. 57%，p < 0.001）；相对于住院治疗的总体 VE 为 53%（95% CI：46%-60%）。汇总 5 个季节的数据，自接种疫苗以来，与流感相关的住院几率每月增加 4.2% (-3.2%-12.2%)，平均 VE 每月下降 1.9% (n = 4,000，p = 0.275)。 ≤8 岁 (n = 3,084) 和 9-17 岁儿童的住院几率每月增加 2.9% (95% CI: -5.4%-11.8%) 和 9.6% (95% CI: -7.0%-29.1%) （n = 916），分别。这些发现没有统计学意义。结论 我们观察到 VE 的季节内下降幅度很小，但没有统计学意义。 遵循当前 ACIP 疫苗接种时间指南进行疫苗接种仍然是预防儿童流感相关住院的最佳策略。