School of Public Health and Community Medicine, Faculty of Medicine, University of New South Wales, Sydney, Australia.
Influenza Other Respir Viruses. 2011 May;5(3):170-9. doi: 10.1111/j.1750-2659.2011.00198.x. Epub 2011 Jan 27.
We compared the efficacy of medical masks, N95 respirators (fit tested and non fit tested), in health care workers (HCWs).
A cluster randomized clinical trial (RCT) of 1441 HCWs in 15 Beijing hospitals was performed during the 2008/2009 winter. Participants wore masks or respirators during the entire work shift for 4 weeks. Outcomes included clinical respiratory illness (CRI), influenza-like illness (ILI), laboratory-confirmed respiratory virus infection and influenza. A convenience no-mask/respirator group of 481 health workers from nine hospitals was compared.
The rates of CRI (3·9% versus 6·7%), ILI (0·3% versus 0·6%), laboratory-confirmed respiratory virus (1·4% versus 2·6%) and influenza (0·3% versus 1%) infection were consistently lower for the N95 group compared to medical masks. By intention-to-treat analysis, when P values were adjusted for clustering, non-fit-tested N95 respirators were significantly more protective than medical masks against CRI, but no other outcomes were significant. The rates of all outcomes were higher in the convenience no-mask group compared to the intervention arms. There was no significant difference in outcomes between the N95 arms with and without fit testing. Rates of fit test failure were low. In a post hoc analysis adjusted for potential confounders, N95 masks and hospital level were significant, but medical masks, vaccination, handwashing and high-risk procedures were not.
Rates of infection in the medical mask group were double that in the N95 group. A benefit of respirators is suggested but would need to be confirmed by a larger trial, as this study may have been underpowered. The finding on fit testing is specific to the type of respirator used in the study and cannot be generalized to other respirators.
Australian New Zealand Clinical Trials Registry (ANZCTR), ACTRN: ACTRN12609000257268 (http://www.anzctr.org.au).
我们比较了医用口罩、N95 呼吸器（适配和不适配）在医护人员中的效果。
这是一项针对 2008-2009 年冬季北京 15 家医院的 1441 名医护人员的群组随机临床试验（RCT）。参与者在整个工作班次中连续佩戴口罩或呼吸器 4 周。结果包括临床呼吸道疾病（CRI）、流感样疾病（ILI）、实验室确诊的呼吸道病毒感染和流感。我们还比较了来自 9 家医院的 481 名医护人员的便利无口罩/呼吸器组。
N95 组的 CRI（3.9%对 6.7%）、ILI（0.3%对 0.6%）、实验室确诊的呼吸道病毒（1.4%对 2.6%）和流感（0.3%对 1%）感染率均低于医用口罩组。意向治疗分析表明，当对聚类进行 P 值调整时，非适配 N95 呼吸器对 CRI 的保护作用明显优于医用口罩，但其他结果均无统计学意义。便利无口罩组的所有结果发生率均高于干预组。适配和不适配 N95 呼吸器之间的结果无显著差异。适配失败率较低。在调整潜在混杂因素的事后分析中，N95 口罩和医院级别是显著的，但医用口罩、疫苗接种、洗手和高风险操作不是。
口罩组的感染率是 N95 组的两倍。建议使用呼吸器，但需要更大规模的试验来证实，因为本研究可能效力不足。适配测试的结果仅适用于研究中使用的呼吸器类型，不能推广到其他呼吸器。
澳大利亚新西兰临床试验注册中心（ANZCTR），ACTRN：ACTRN12609000257268（http://www.anzctr.org.au）。
