BACKGROUND Influenza vaccine effectiveness (VE) varies by season, circulating influenza strain, age, and geographic location. There have been few studies of influenza VE among hospitalized children, particularly in Europe and the Middle East. METHODS We estimated VE against influenza hospitalization among children aged 6 months to 8 years at Clalit Health Services hospitals in Israel in the 2015-2016, 2016-2017, and 2017-2018 influenza seasons, using the test-negative design. Estimates were computed for full and partial vaccination. RESULTS We included 326 influenza-positive case patients and 2821 influenza-negative controls (140 case patients and 971 controls from 2015-2016, 36 case patients and 1069 controls from 2016-2017, and 150 case patients and 781 controls from 2017-2018). Over all seasons, VE was 53.9% for full vaccination (95% confidence interval [CI], 38.6%-68.3%), and 25.6% for partial vaccination (-3% to 47%). In 2015-2016, most viruses were influenza A(H1N1) and vaccine lineage-mismatched influenza B/Victoria; the VE for fully vaccinated children was statistically significant for influenza A (80.7%; 95% CI, 40.3%-96.1%) but not B (23.0%; -38.5% to 59.4%). During 2016-2017, influenza A(H3N2) predominated, and VE was (70.8%; 95% CI, 17.4%-92.4%). In 2017-2018, influenza A(H3N2), H1N1 and lineage-mismatched influenza B/Yamagata cocirculated; VE was statistically significant for influenza B (63.0%; 95% CI, 24.2%-83.7%) but not influenza A (46.3%; -7.2% to 75.3%). CONCLUSIONS Influenza vaccine was effective in preventing hospitalizations among fully vaccinated Israeli children over 3 influenza seasons, but not among partially vaccinated children. There was cross-lineage protection in a season where the vaccine contained B/Victoria and the circulating strain was B/Yamagata, but not in a season with the opposite vaccine-circulating strain distribution.

中文翻译：

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以色列针对部分和部分疫苗接种的儿童的住院疫苗的流感疫苗有效性：2015-2016年，2016-2017年和2017-2018年。

背景技术流感疫苗的有效性（VE）随季节，流行的流感病毒株，年龄和地理位置而变化。在住院儿童中，尤其是在欧洲和中东地区，关于VE流感的研究很少。方法我们使用测试阴性设计估计了2015-2016年，2016-2017年和2017-2018年流感季节在以色列Clalit卫生服务医院的6个月至8岁儿童中的VE对流感住院的影响。计算了全部和部分疫苗接种的估计数。结果我们纳入了326例流感阳性病例患者和2821例阴性阴性对照组（2015-2016年为140例患者和971例对照，2016-2017年为36例患者和1069例对照，以及2017-2018年为150例患者和781例对照） 。在所有季节中，VE均为53。完全疫苗接种率为9％（95％置信区间[CI]，38.6％-68.3％），部分疫苗接种为25.6％（-3％至47％）。在2015-2016年，大多数病毒为A型流感（H1N1）和疫苗谱系不匹配的B型/维多利亚流感；完全接种疫苗的儿童的VE在甲型流感（80.7％； 95％CI，40.3％-96.1％）中有统计学意义，而在乙型流感中则无统计学意义（23.0％；-38.5％至59.4％）。在2016-2017年期间，甲型H3N2流感占主导地位，VE为（70.8％; 95％CI，17.4％-92.4％）。在2017-2018年期间，甲型H3N2流感，H1N1流感和谱系不匹配的乙型/山形流感共同流行; VE在乙型流感中具有统计学意义（63.0％; 95％CI，24.2％-83.7％），但在A型流感中则无统计学意义（46.3％; -7.2％至75.3％）。结论流感疫苗可有效预防3个流感季节以上已完全接种疫苗的以色列儿童的住院，但未接种部分疫苗的儿童除外。在疫苗中含有B / Victoria且传播株为B / Yamagata的季节中有跨谱系保护，但在疫苗流通株分布相反的季节中则没有交叉谱系保护。