美国匹兹堡疾控中心Lewis J. Radonovich与合作者在最新研究中，比较了N95口罩与医用口罩预防流行性感冒及其他病毒性呼吸道感染的效果。相关论文发表在9月3日出版的《美国医学会杂志》上。

2011年9月至2015年5月，研究组在美国7个医疗中心的137个门诊点进行了一项集群、随机、实用、有效性研究，并于2016年6月进行了最终随访。2862名医务人员（HCP）的平均年龄为43岁，82.8%为女性，当接诊呼吸系统疾病患者时随机佩戴N95口罩或医用口罩，最终有2371名完成了研究，共5180个HCP季。

N95口罩组发生207例实验室确认的流感感染事件（占HCP季的8.2%），医用口罩组有193例（占HCP季的7.2%），校正优势比为1.18；N95口罩组中发生急性呼吸系统疾病1556例，医用口罩组为1711例，差异为每1000HCP季-21.9；N95口罩组中发生679例实验室检测到的呼吸道感染，医用口罩组为745例，差异为-8.9；N95口罩组中发生371例实验室确认的呼吸疾病，医用口罩组为417例，差异为-8.6；N95口罩组中发生128起流感样疾病事件，医用口罩组为166起，差异为-11.3。

在N95口罩组中，89.4%的参与者“总是”或“有时”戴口罩，而在医用口罩组中，这一比例为90.2%。

综合来看，门诊医护人员佩戴N95口罩相比医用口罩并未显著降低流感发病率。

附：英文原文

Title: N95 Respirators vs Medical Masks for Preventing Influenza Among Health Care Personnel  A Randomized Clinical Trial

Author: Lewis J. Radonovich Jr, MD1; Michael S. Simberkoff, MD2,3; Mary T. Bessesen, MD4,5; Alexandria C. Brown, PhD6; Derek A. T. Cummings, PhD7,8; Charlotte A. Gaydos, MD9; Jenna G. Los, MLA9; Amanda E. Krosche, BS9,10; Cynthia L. Gibert, MD11,12; Geoffrey J. Gorse, MD13,14; Ann-Christine Nyquist, MD5,15; Nicholas G. Reich, PhD6; Maria C. Rodriguez-Barradas, MD16,17; Connie Savor Price, MD5,18; Trish M. Perl, MD8,19; for the ResPECT investigators

Issue&Volume: Vol 322 No 9

Abstract：

Importance  Clinical studies have been inconclusive about the effectiveness of N95 respirators and medical masks in preventing health care personnel (HCP) from acquiring workplace viral respiratory infections.

Objective  To compare the effect of N95 respirators vs medical masks for prevention of influenza and other viral respiratory infections among HCP.

Design, Setting, and Participants  A cluster randomized pragmatic effectiveness study conducted at 137 outpatient study sites at 7 US medical centers between September 2011 and May 2015, with final follow-up in June 2016. Each year for 4 years, during the 12-week period of peak viral respiratory illness, pairs of outpatient sites (clusters) within each center were matched and randomly assigned to the N95 respirator or medical mask groups.

Interventions  Overall, 1993 participants in 189 clusters were randomly assigned to wear N95 respirators (2512 HCP-seasons of observation) and 2058 in 191 clusters were randomly assigned to wear medical masks (2668 HCP-seasons) when near patients with respiratory illness.

Main Outcomes and Measures  The primary outcome was the incidence of laboratory-confirmed influenza. Secondary outcomes included incidence of acute respiratory illness, laboratory-detected respiratory infections, laboratory-confirmed respiratory illness, and influenzalike illness. Adherence to interventions was assessed.

Results  Among 2862 randomized participants (mean [SD] age, 43 [11.5] years; 2369 [82.8%]) women), 2371 completed the study and accounted for 5180 HCP-seasons. There were 207 laboratory-confirmed influenza infection events (8.2% of HCP-seasons) in the N95 respirator group and 193 (7.2% of HCP-seasons) in the medical mask group (difference, 1.0%, [95% CI, −0.5% to 2.5%]; P = .18) (adjusted odds ratio [OR], 1.18 [95% CI, 0.95-1.45]). There were 1556 acute respiratory illness events in the respirator group vs 1711 in the mask group (difference, −21.9 per 1000 HCP-seasons [95% CI, −48.2 to 4.4]; P = .10); 679 laboratory-detected respiratory infections in the respirator group vs 745 in the mask group (difference, −8.9 per 1000 HCP-seasons, [95% CI, −33.3 to 15.4]; P = .47); 371 laboratory-confirmed respiratory illness events in the respirator group vs 417 in the mask group (difference, −8.6 per 1000 HCP-seasons [95% CI, −28.2 to 10.9]; P = .39); and 128 influenzalike illness events in the respirator group vs 166 in the mask group (difference, −11.3 per 1000 HCP-seasons [95% CI, −23.8 to 1.3]; P = .08). In the respirator group, 89.4% of participants reported “always” or “sometimes” wearing their assigned devices vs 90.2% in the mask group.

Conclusions and Relevance  Among outpatient health care personnel, N95 respirators vs medical masks as worn by participants in this trial resulted in no significant difference in the incidence of laboratory-confirmed influenza.