【Cochrane简语概要】健康儿童预防流感疫苗

研究目的 

2007年首次发表的Cochrane综述的目的是：总结在流感季节使用流感疫苗对16岁以下的健康儿童进行免疫的研究。我们使用随机试验比较两种疫苗中的任何一种与安慰剂或不使用疫苗相比。一种疫苗是基于活的但被减弱的流感病毒（活减毒流感疫苗），并通过鼻子接种。另一种是通过使用化学物质杀死流感病毒（灭活流感疫苗），并通过皮肤注射接种。我们分析了确诊为流感和患流感样疾病（头痛、高温、咳嗽和肌肉疼痛）以及接种疫苗后出现危害的儿童的数量。只有新的试验发表时才会进一步更新这项系统综述。由于历史原因保留了以前版本的33项观察性研究报告的数据，但因对综述结论没有影响而未予更新。

（图片来源于网络）

关键信息 

减毒和灭活疫苗可降低患流感和流感样症状的儿童的比例。研究结果的变化意味着我们不确定这些疫苗在不同季节所产生的影响。

该综述研究了什么？ 

超过200种病毒会导致流感样疾病，并产生相同的症状（发烧、头痛、疼痛、咳嗽和流鼻涕）。没有实验室检测，医生无法区分它们，因为它们都是持续数天，且很少导致严重疾病或死亡。

根据世界卫生组织（季节性疫苗）的建议，疫苗中所含的病毒的种类通常是那些预计在接下来的流感季节中会流行的病毒。大流行性流感疫苗只含有导致大流行流感的病毒株（例如2009年至2010年大流行的A型H1N1病毒）。

主要结果 

我们发现了41项随机研究。大多数研究包括年龄在两岁以上的儿童， 并在美国、西欧、俄罗斯和孟加拉国进行。

与安慰剂或不使用疫苗相比，减毒活疫苗可能使确诊为流感的儿童比例从18%降至4%（中度确定性证据），并可能使流感样症状从17%降至12%（低度确定性证据）。需要接种的七个孩子中会有一个孩子免遭受流感，20个孩子中会有1个孩子免患上流感样疾病。我们从一项研究中发现的数据显示，两组患耳朵感染的风险相似。没有足够的资料来评估学校缺勤和父母需要请假的情况。我们没有发现住院的数据，也没有持续报告危害。

与安慰剂或不接种疫苗相比，灭活疫苗可将流感风险从30%降低至11%（高度确定性证据），而且可能将患流感样疾病的风险从28%降低至20%（中度确定性证据）。需要接种的5个孩子中会有1个孩子免遭受流感，12个孩子中会有1个孩子免患上流感样疾病。接种过疫苗的儿童和未接种过疫苗的儿童患中耳炎的风险可能是相似的（31% vs 27%，中度确定性证据）。由于一项研究中非常不确定的证据，故没有足够的资料来评估学校缺勤情况。我们没有发现父母工作时间减少、住院、发烧或恶心的数据。

一种品牌的大流行性单价流感疫苗与儿童剧烈情绪（昏厥）和睡眠障碍（嗜睡症）引发的肌张力突然丧失有关。

只有少数研究是精心设计和实施的，偏倚风险高的研究对评估结果的影响各不相同。流感和中耳炎是唯一的结果，偏倚没有影响我们对结果的信心。

本综述的时效性如何？ 

证据截止到2016年12月31日。

结论: 

在3至16岁的儿童中，活疫苗可能会在一个流感季节中减少流感的发生（中度确定性证据），并可能减少流感样疾病的发生（低确定性证据）。在这个群体中，灭活疫苗也可以减少流感的发生（高确定性证据），并可能减少流感样疾病的发生（低确定性证据）。对于这两种疫苗，流感和流感样疾病的绝对减少在不同的研究人群中存在着很大的差异，因此很难预测这些结果在不同的环境下是如何变化的。我们发现很少有针对两岁以下儿童进行的随机对照试验。在现有研究中，不良事件数据没有得到很好的描述。对不良事件的定义、确定和报告需要进行标准化处理。查明所有潜在危害的全球病例超出了本综述的范围。

【Cochrane Plain Language Summary】Vaccines for preventing influenza in healthy children

Review aim 

The aim of this Cochrane Review, first published in 2007, was to summarise research on immunising healthy children up to the age of 16 with influenza vaccines during influenza seasons. We used randomised trials comparing either one of two types of vaccines with dummy vaccines or nothing. One type of vaccine is based on live but weakened influenza viruses (live attenuated influenza vaccines) and is given via the nose. The other is prepared by killing the influenza viruses with a chemical (inactivated virus) and is given by injection through the skin. We analysed the number of children with confirmed influenza and those who had influenza-like illness (ILI) (headache, high temperature, cough, and muscle pain) and harms from vaccination. Future updates of this review will be made only when new trials or vaccines become available. Data from 33 observational studies included in previous versions of the review have been retained for historical reasons but have not been updated due to their lack of influence on the review conclusions.

Key messages

Live attenuated and inactivated vaccines can reduce the proportion of children who have influenza and ILI. Variation in the results of studies means that we are uncertain about the effects of these vaccines across different seasons.

What was studied in this review? 

Over 200 viruses cause ILI and produce the same symptoms (fever, headache, aches, pains, cough, and runny nose) as influenza. Doctors cannot distinguish between them without laboratory tests because both last for days and rarely cause serious illness or death.

The types of virus contained in the vaccines are usually those that are expected to circulate in the following influenza seasons, according to recommendations of the World Health Organization (seasonal vaccine). Pandemic vaccine contains only the virus strain that is responsible for the pandemic (e.g. the type A H1N1 for the 2009 to 2010 pandemic).

Main results 

We found 41 randomised studies. Most studies included children older than two years of age and were conducted in the USA, Western Europe, Russia, and Bangladesh.

Compared with placebo or do nothing, live attenuated vaccines probably reduced the proportion of children who had confirmed influenza from 18% to 4% (moderate-certainty evidence), and may reduce ILI from 17% to 12% (low-certainty evidence). Seven children would need to be vaccinated for one child to avoid influenza, and 20 children would need to prevent one child from experiencing an ILI. We found data from one study that showed similar risk of ear infection in the two groups. There was insufficient information available to assess school absence and parents needing to take time off work. We found no data on hospitalisation, and harms were not consistently reported.

Compared with placebo or no vaccination, inactivated vaccines reduce the risk of influenza from 30% to 11% (high-certainty evidence), and they probably reduce ILI from 28% to 20% (moderate-certainty evidence). Five children would need to be vaccinated for one child to avoid influenza, and 12 children would need to be vaccinated to prevent one case of ILI. The risk of otitis media is probably similar between vaccinated children and unvaccinated children (31% versus 27%, moderate-certainty evidence). There was insufficient information available to assess school absenteeism due to very low-certainty evidence from one study. We identified no data on parental working time lost, hospitalisation, fever, or nausea.

One brand of monovalent pandemic vaccine was associated with a sudden loss of muscle tone triggered by the experience of an intense emotion (cataplexy) and a sleep disorder (narcolepsy) in children.

Only a few studies were well designed and conducted, and the impact of studies at high risk of bias varied across the outcomes evaluated. Influenza and otitis media were the only outcomes where our confidence in the results was not affected by bias.

How up to date is this review?

The evidence is current to 31 December 2016.

Authors' conclusions: 

In children aged between 3 and 16 years, live influenza vaccines probably reduce influenza (moderate-certainty evidence) and may reduce ILI (low-certainty evidence) over a single influenza season. In this population inactivated vaccines also reduce influenza (high-certainty evidence) and may reduce ILI (low-certainty evidence). For both vaccine types, the absolute reduction in influenza and ILI varied considerably across the study populations, making it difficult to predict how these findings translate to different settings. We found very few randomised controlled trials in children under two years of age. Adverse event data were not well described in the available studies. Standardised approaches to the definition, ascertainment, and reporting of adverse events are needed. Identification of all global cases of potential harms is beyond the scope of this review.

译者：楼蓉，东阳市人民医院；审校：李静，北京中医药大学循证医学中心；编辑排版：张晓雯，北京中医药大学循证医学中心

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