During an influenza pandemic, health care workers are the soldiers of a global infection control battlefield. When most people are advised to find ways to avoid social gatherings and minimize contact with others, health care workers seek to position themselves on the front line, in crowded emergency rooms and busy hospital wards. These surroundings are chosen while sacrificing the relative safety of their homes and even risking the well-being of their families.
The correct armor needed to protect health care workers from the munitions of an influenza surge is not known. In fact, it has never been known. During the 1918 influenza pandemic, the same questions were asked about preventing influenza transmission between people.Reference Crosby1 Then, as now, masks became a widely used means of protection, albeit with considerable controversy. In 2009, the ensuing controversy has permeated nearly every aspect of preparedness for the H1N1 pandemic and stands to leave the public with the somewhat warranted conclusion that the nation’s research and public health communities and health care delivery systems have not competently prepared for the events that are unfolding.
PUBLIC HEALTH RECOMMENDATIONS AND CONTROVERSY IN THE FACE OF UNCERTAINTY
From the time when a swine-origin novel H1N1 influenza A virus (hereafter referred to as novel H1N1) was first recognized as an epidemic in Mexico, the Centers for Disease Control and Prevention (CDC) has recommended that health care workers protect themselves from suspected or confirmed victims by wearing N95 respirators (filtering facepiece respirators with filters capable of trapping at least 95% of particulates).2 At the time this article went to press, these recommendations continued to cause considerable controversy and criticism. One collective voice of opposition has questioned why respirators are necessary for the current pandemic when seasonal influenza infection control recommendations call for wearing surgical masks, not N95 respirators.
Respiratory infection prevention and control precautions, including the use of surgical masks and respirators, are based on the mode of human-to-human transmission exhibited by the microorganism.3 When an organism is believed to be transmitted by large, heavier droplets instead of smaller aerosols that remain suspended in the air, droplet respiratory precautions (surgical masks) are typically recommended.3 When transmitted via the air, airborne respiratory precautions (respirators) are typically recommended.3 Airborne microorganisms may be transmitted from person to person by small (≤5 μm in aerodynamic diameter) particulates called droplet nuclei that consist of virus and respiratory secretions.4 Droplet nuclei are a type of aerosol that can be carried from place to place via normal indoor currents of air. N95 respirators are designed to capture droplet nuclei, preventing them from coming into contact with the respiratory tract of the wearer.4 Accordingly, N95 respirators are evaluated and certified by the National Institute of Occupational Safety and Health (NIOSH) regarding their capabilities to filter at least 95% of particulates measuring 0.3 μm in aerodynamic diameter.5 Based on the principles of particle physics, these respirators have also been shown to filter smaller aerosols (eg, 0.04 μm in aerodynamic diameter), the size of a single viron.Reference Sutherland6
CDC has for years recommended the use of surgical masks for seasonal outbreaks of influenza that occur annually.3 This recommendation stands in direct contradiction to the novel H1N1 pandemic recommendations, which have called for respirators, not surgical masks. Importantly, seasonal influenza recommendations have been based on limited laboratory and clinical evidence that suggests seasonal influenza is primarily spread from person to person by contact or large droplets (>5 μm in aerodynamic diameter). Reference Lemieux, Brankston, Gitterman, Hirji and Gardam7–9 A body of evidence suggests, however, that seasonal influenza may actually be spread from person to person via droplet nuclei.Reference Sandrock and Stollenwerk10–Reference Atkinson and Wein15 In truth, the scientific community does not understand precisely how influenza is spread from person to person; it may be multimodal. Still, the CDC has not changed their seasonal influenza recommendations, from surgical masks to N95 respirators, presumably because the evidence for airborne transmission remains uncertain and the established practice weighs in favor of surgical masks.
Where there is uncertainty about seasonal influenza, there is substantially more uncertainty about pandemics caused by influenza. Whether a novel strain of influenza, to which few or no people have immunity, is primarily spread via large or small droplets has never been known during the early stages of an outbreak. CDC’s initial policy suggested they believed it prudent to recommend the use of N95 respirators until the emergence of evidence proving the novel H1N1 virus is not transmitted from person to person by droplet nuclei. If public health organizations were to use the counterapproach, recommending that health care workers not use N95 respirators until there is evidence that novel H1N1 is transmitted from person to person by droplet nuclei, they could be wrong and leave many employees unprotected against a disease that can be fatal. Under such circumstances, many public health agencies believe the best choice is a cautious one.
N95 respirators pose a number of important challenges. They require Occupational Safety and Health Administration (OSHA)–compliant fit testing,16 typically produce discomfort to which health care workers become intolerant with prolonged use,17, 61 may interfere with occupational duties,Reference Yassi18 and can cause diminished speech intelligibility.17 Another challenge for health care institutions is acquiescing to respirator manufacturers’ limited production capacity and adapting to a constrained number of respirators available in emergency-use stockpiles. Reliable estimates indicate that there would be a global shortage of filtering facepiece (disposable) N95 respirators during a severe pandemic,19 if respirators were frequently discarded in a fashion compliant with OSHA regulations5 and CDC guidelines.4 Furthermore, many health departments and health care systems have reported insufficient funds to equip every health care worker with OSHA-compliant N95 respirators.20
It seems the real reason underlying the controversy about respiratory protection during a pandemic is a fundamental disconnection that often exists between health policy formulation and knowledge discovery using the scientific method. In an ideal world, policies would not be codified until scientific evidence illuminates the best and most correct practices. Unfortunately, the need for practical answers often precedes and supersedes the availability of sound scientific data, leading governance organizations to issue recommendations that often evolve into the “standard of care,” despite minimal or no supportive scientific evidence. Once a standard of care is set, however unsound, it becomes essentially unethical to conduct studies that directly test its validity.Reference Shapiro and Meslin21 Many in health care are all too aware of this phenomenon and fear that CDC’s willingness to recommend N95 respirators could lead to expanding but unsubstantiated indications for N95 respirators. Traveling down this pathway could precipitate a milieu in which it becomes unethical to conduct a definitive clinical trial that determines whether N95 respirators are more effective than surgical masks against influenza transmission. What has evolved with novel H1N1 may be called a stalemate. Bolstered by the health care unions and a risk-averse culture, CDC was pressured to initially recommend N95 respirators as primary protection against novel H1N1.22 Subsequently, CDC was pressured to change its recommendation from N95 respirators to surgical masks,20 bolstered by health care professional societies, numerous financially insolvent health departments, and the emergence of limited evidence suggesting novel H1N1 is a moderately virulent virus.
THE CLINICAL SCIENCE OF RESPIRATOR USE IN HEALTH CARE: WHAT WE KNOW AND WHAT WE DO NOT KNOW
In the late 1980s, tuberculosis resurgence in the United States prompted increased attention to infection control in health care.23 Before this event, respirator use among health care workers was rare.Reference Radonovich, Hodgson and Cohen24, Reference Jarvis, Bolyard and Bozzi46 As US hospitals became increasingly populated with patients with tuberculosis, the number of exposed health care workers increased accordingly.Reference Pearson, Jereb and Frieden25 Numerous health care workers became infected with tuberculosis from occupational exposures and several died.26
Calls for action to improve infection control in US hospitals prompted the CDC to recommend the use of respiratory protection when caring for tuberculosis-infected patients.4 Although there was insufficient evidence available to deem adequate a certain type of respiratory protection, in 1994 the CDC elected to call for respirators with an “ability to filter particles 1 μm in size . . . with a filter efficiency of ≥95%.”4 This was followed by OSHA regulations that used more rigid language and threatened enforcement with financial penalties for noncompliance.27 These measures ushered in a standard of care that was not grounded in clinical science. In fact, N95 respirators selected to protect against tuberculosis were never specifically designed for health care workers. Instead, they were borrowed from the manufacturing and construction industries because of a need for immediate action in the face of resurgent tuberculosis.Reference Jarvis, Bolyard and Bozzi46 Because the most widely used respirators in health care were not designed for health care delivery, it should not be surprising that they are poorly tolerated and widely viewed as uncomfortable.
Extensive laboratory-based research has been performed to understand the extent of protection offered by respirators. These laboratory-based studies are typically performed with surrogate measures and/or in simulated settings that attempt to resemble health care delivery.Reference Lee, Grinshpun and Reponen28 Although these studies are important for the development of respiratory protective equipment, they do not produce results that are essential to determine effectiveness in a clinical setting.Reference Nicas29
NIOSH certification of N95 respirators30 is primarily based on laboratory testing of filter efficiency along with a determination that the resistance caused by inhalation and exhalation while wearing the respirator meets standards that would be tolerated by most workers. Interestingly, N95 respirators (and all other filtering facepiece respirators) are the only class of negative-pressure respirators that are not routinely assessed for their ability to fit the wide variety of faces found in the working population. Accordingly, NIOSH certification is not tethered to N95 “adequacy of fit.” As a result, laboratory studies to date have shown that there is a wide variability in performance among N95 respirators that is dependent on their capability to fit users.Reference Coffey, Campbell and Zhuang31, Reference Coffey, Lawrence, Campbell, Zhuang, Calvert and Jensen32 These laboratory-based studies are sometimes referred to as simulated workplace protection factor tests or total inward leakage tests. One recently published laboratory study has shown that most of the aerosol contaminants that enter the respirator are the result of facepiece leakage and not filter performance,Reference Grinshpun, Haruta and Eninger33 an assumption that has been made for years. Furthermore, this leakage is a function of the size of the aerosol particles, with larger particles producing less facepiece leakage. In sum, different types of N95 respirators cannot be expected to perform equally and respirator performance can be expected to primarily depend on facepiece leakage, not filter performance, and the size of particulate aerosols in the workplace.
Medical masks (often called surgical masks) cover a broad range of respiratory devices that may or may not be Food and Drug Administration (FDA)–approved and are not designed to closely seal to the user’s face. Although surgical masks were designed to protect others from being contaminated by the wearer’s respiratory secretions, many health care workers wear them to protect themselves. Accordingly, FDA approval is contingent on demonstrating that the mask (typically made of filter material) provides protection to the wearer from splashes, flammability, and aerosol penetration through the filter.34 Because surgical masks are not designed to provide a seal to the user’s face, they do not require fit testing. Surgical masks can be used by individuals with a wide range of facial sizes and by those with facial hair (eg, beards) that preclude proper fitting of filtering facepiece respirators. FDA, unlike NIOSH, does not perform any testing on surgical masks but requires34 that manufacturers apply for 510(k) (medical device submission) approval, demonstrating that the masks either meet requirements set forth by existing voluntary standards35 or demonstrate equivalent performance with the established standard. FDA also requires that resistance to airflow testing be performed and that the mask be labeled according to the thermal discomfort the user should expect while wearing the device. For manufacturers to make medical claims about respirators or surgical masks, they must be FDA approved. Although respirators and surgical masks are often used in the health care sector without FDA approval, many would espouse the added value of FDA’s role.
There have been a variety of laboratory tests comparing the performance of N95 respirators and surgical masks, including the effectiveness of filter materials and total inward leakage exhibited by the devices. Although the results vary depending on the laboratory test conditions, masks demonstrate more leakage of aerosol contaminants (less protection) than respirators, in all studies.Reference Lawrence, Duling, Calvert and Coffey36–Reference Gawn, Clayton, Makison and Crook41 These studies have been done with small aerosols that are <5 μm. A study by Oberg et al indicated that the filter materials used in surgical masks perform better as the size of the aerosol approached 5 μm.Reference Oberg and Brosseau38 However, Grinshpun et al have recently studied filters and facepiece leakage performance of a surgical mask at 3 aerosol sizes and found that leakage was independent of aerosol size (all 3 sizes were <5 μm).Reference Grinshpun, Haruta and Eninger33
NIOSH in 1995 changed their N95 certification requirements for filter testing and now uses a “most penetrating particle size” aerosol (0.3 μm),42 recognizing that employers at most workplaces do not know or measure the aerosol size to which workers are exposed. This is precisely the issue for health care workers who are exposed to influenza. It may be that surgical masks provide infection protection to these workers as a combination of keeping workers from touching their nose and mouth with their hands and also providing a level of respiratory protection. Laboratory studies can inform practice guidelines in this regard; however, only field (clinical) studies can validate whether respirators or masks deliver adequate protection. Field studies have been the basis for assigning respirator protection factors by the American Nationals Standards Institute43 and OSHA,44 because these organizations recognize the limitations of laboratory studies.
The use of risk assessment processes to choose respiratory protection for influenza and other infectious diseases does not fit the normal paradigm used by industrial hygienists. Hazardous exposures that require workers to wear respirators typically have occupational exposure limits (the upper limit to which workers can safely be exposed). Workplace monitoring or modeling is used to estimate workplace exposure levels. The ratio of the workplace exposure level to the occupational exposure limit provides a hazard ratio or risk assessment to optimally choose the proper type of respirator. In the case of influenza (and most other biological hazards), there is neither a known occupational exposure limit nor workplace monitoring data. This further accentuates the need for workplace validation (field studies) of personal protective equipment to demonstrate whether it is adequate for a particular hazard. A recent Institute of Medicine publication that examined the need for preparing for an influenza pandemic made this recommendation.17
Unfortunately, few field studies have been done to determine the extent to which respirators protect health care workers against airborne infectious diseases. Some of the data that do exist do not weigh in favor of meaningful protection.Reference Radonovich, Hodgson and Cohen24, 45 Because the respiratory protection standard was founded in an urgent fashion, driven by a need for policy with minimal input from science, there was not sufficient time to complete definitive clinical trials before widespread respirator use.45 Furthermore, the data that became available after the new standard was implemented were challenging to interpret.Reference Jarvis, Bolyard and Bozzi46 The 1994 guidelines recommended by CDC called for implementing a wide range of infection control measures,4 including engineering measures, administrative measures, and personal protective equipment. Because all 3 were implemented simultaneously, it became challenging if not impossible to examine 1 intervention minus the other 2.
In 2000, Menzies et al looked at the effects of the new standard.Reference Menzies, Fanning, Yuan and Fitzgerald47 They found that infection control failures subsequent to 1994 were associated with inadequate clinical practice, such as failure to identify cases early enough, rather than a failure to wear respirators. In addition, the Institute of Medicine concluded in 2001 that “personal respirators did not appear to play a significant role in ending outbreaks of TB [tuberculosis].”45 Furthermore, although CDC calls for N95 respirator use when health care workers may be exposed to monkey pox, anthrax, viral hemorrhagic fevers, and smallpox,3 there is essentially no clinical evidence that respirators prevent these illnesses. In such cases, the precept is that the combined likelihood of airborne transmission and severe illness, including death, is sufficient to justify regular use of respirators even if they may have little effect.
The severe acute respiratory syndrome (SARS) outbreak in 2003 served as a test bed for respiratory protection effectiveness. Despite the outbreak occurring suddenly, clinical investigators were able to conduct a number of provisional studies. A case-control study in Hong KongReference Seto, Yung, Ching, Ng, Ho and Peris48 demonstrated that people who did not become infected with SARS were likely to have worn facemasks and gowns and performed regular hand hygiene. This study, however, did not discriminate between N95 respirators and surgical masks. Lau et alReference Lau, Tsui, Lau and Yang49 reported that individuals who did not become infected with SARS were likely to have self-reported wearing a mask in public venues and performing frequent hand-washing. A study by Teleman et al was 1 of 2 SARS-era studies that differentiated N95 masks from other nonpharmaceutical protective measures.Reference Teleman, Boudville, Heng, Zhu and Leo50 Among 94 health care workers with probable or suspected SARS, the odds that they wore an N95 respirator was 0.10 (95% confidence interval [CI] 0.02–0.86) compared to not wearing a respirator. In a similar study of 43 SARS-exposed nurses, Loeb et al found the odds that they wore an N95 respirator, compared to no protection, was 0.22 (95% CI 0.05–0.93].Reference Loeb, McGeer and Henry51 Loeb et al further found that the odds that they wore a surgical mask, compared to no respiratory protection, was 0.45 (95% CI 0.07–2.71).Reference Loeb, McGeer and Henry51 Unfortunately, the data available from the SARS outbreak were not sufficient to conclusively determine whether N95 respirators were superior in performance to surgical masks for the SARS coronavirus.
McIntyre et alReference MacIntyre, Cauchemez and Dwyer52 attempted to quantify the effectiveness of respirators compared to surgical masks and no respiratory protection in the homes of patients with influenza-like illness. This study suggests that surgical masks or respirators (whether fit tested or not) reduced the risk of illness reported by the wearers over those who used no masks; however, subject compliance was poor and this study was not powered to discriminate between the effects of surgical masks and respirators.
Additional clinical studies have been completed recently or are occurring at the time of this writing; however, objective analysis of the findings has not been conducted by the wider scientific community because the results have not yet appeared in the literature.
RESPIRATOR USE IN THE FUTURE: IMPLICATIONS IN THE ABSENCE OF CLINICAL TRIALS
Since about 1994, when respirators were first formally instituted in health care, the trend has been toward broadening the indications for their use.3 Concerns about the pandemic potential of the H5N1 (avian) influenza virus and more recently the novel H1N1 pandemic suggest that influenza may be the next microorganism for which respirators become mandatory in the United States. Guidelines about the transmission risk associated with seasonal influenza called for droplet precautions, including surgical masks,Reference Garner53 for decades before 2007, when new guidance was written about pandemic scenarios.3, 4 In the absence of well-designed clinical trials, it seems plausible that a gradual shift in clinical practice, driven by general public health recommendations rather than science, could occur such that the use of N95 respirators becomes the infection control standard of care for all cases of influenza or influenza-like illness in the United States. What would be the implications if respirators become widely used in this fashion? Certain consequences may be somewhat unexpected, as in the following paragraphs.
It has been estimated that seasonal influenza typically has a low annual incidence of about 2.5% in the United States.54 Nonspecific respiratory illnesses, sometimes called common colds, are much more prevalent among Americans, causing approximately 2 to 4 episodes per year per person, on average.55, Reference Turner56 Assuming that 3.5% of Americans seek outpatient health care57 when they have a respiratory illnesses, 31.5 million outpatient visits per year would require the use of respirators by every health care worker involved. At a cost of approximately $0.75 each (for disposable models), the subtotal respirator cost per year for nationwide outpatient services would be approximately of $23.6 million.
Assuming that approximately 228,635 Americans are hospitalized annually for influenzaReference Thompson, Shay and Weintraub58 and each health care worker would need to don a new respirator with each patient contact,3 approximately 184 disposable respirators would be required for each hospital admission,59 costing approximately $31.6 million per year on a national scale. This approach would cost the nation an extra $55.2 million for respirators during a routine year. During a pandemic, it can be estimated that requirements may be as high as 3 billion respirators59 or $2.25 billion. In a pandemic setting, however, it is likely that respirators would be reused and discarded on a daily (not per-contact) basis.19 These figures do not account for the community or home settings, which would be expected to roughly parallel the needs in the hospitalized population. Therefore, the total financial cost to Americans for hypothetically shifting to widespread disposable N95 use, as a means to protect against influenza and influenza-like illnesses, would be approximately $4.6 billon/year (in the absence of a pandemic). This estimate accounts only for respirators and does not include other infection control equipment that would accompany airborne precautions.
In addition to the financial burden, there would be a substantial physical and emotional toll. Respirators have been associated with poor tolerabilityReference Radonovich, Cheng, Shenal, Hodgson and Bender60; overall discomfortReference Radonovich, Cheng, Shenal, Hodgson and Bender60–Reference Yassi65; diminished visual, 63,66,67 vocal,Reference Khoo, Leng, Ibrahim and Lim66, 67 or auditoryReference Khoo, Leng, Ibrahim and Lim66 acuity; excessive humidityReference Li, Tokura and Guo62 or heatReference Li, Tokura and Guo62,Reference Yassi65,67,Reference Jonas-Simpson68; headaches61, Reference Lim, Seet and Lee69; facial pressureReference Li, Tokura and Guo62; skin irritation or itchiness61,62,67,Reference Jonas-Simpson68; excessive fatigue or exertion61,Reference Li, Tokura and Guo62,Reference Shimozaki, Harber, Barrett and Loisides64,Reference Yassi65,67,Reference Jonas-Simpson68; malodorousnessReference Li, Tokura and Guo62, Reference Yassi65; anxiety or claustrophobia61,Reference Jonas-Simpson68,Reference Bai, Lin and Lin70–Reference Farquharson and Baguley72; and other interferences with occupational duties.Reference Yassi65,Reference Farquharson and Baguley72–Reference Nickell, Crighton and Tracy74 Finally, patients find certain respirator models unusual in appearance,Reference Menzies, Fanning, Yuan and Fitzgerald47,75–Reference Koller, Nicholas, Goldie, Gearing and Selkirk77 possibly interfering with relationships between patients and health care workers. In contrast, although surgical masks can cause limited facial irritation, the frequency and range of health care worker complaints associated with wearing surgical masks is typically lower than with respirators.Reference Radonovich, Cheng, Shenal, Hodgson and Bender60
MOVING BEYOND THE DEBATE TO CONSTRUCTIVE PLANNING
Questions about relative effectiveness cannot be answered by the current debate that has been rendered feckless by equivocacy. Additional clinical research must be conducted to gain new knowledge. If planned thoughtfully, then we could see in the next few years answers to key research questions about influenza transmission and respirator effectiveness, such that science can effectively inform policy.
In the near future, laboratory research should focus on practical questions such as how to efficiently perform user seal checks in the field, how to effectively decontaminate reusable respirators between patient contacts, ways to design respirators that do not interfere with speech intelligibility, and ways to efficiently don and doff respirators without causing self-contamination.
Over the long term, clinical trials are needed to determine the best ways to protect health care workers against airborne infectious diseases. In parallel (to save valuable time) separate efforts must be undertaken to understand which infectious diseases can spread from person to person via the airborne route. These trials are often resource and time intensive and require well-established funding streams before study initiation. In the past, federal streams have been mostly inadequate to fund these types of applied research trials despite their importance. The need to answer key practical questions about airborne diseases has become important enough to justify increased investment of research funds.
To avoid the pitfalls of inadequate practical knowledge in the future, research agendas should include applied research topics that are essential to an effective health care system. When insufficient knowledge creates a gap between science and policy, the national research agenda should fill the gap. Importantly, caution should be exercised to avoid filling the gap with a standard of care that is not grounded in science. On a practical level, perhaps this means that if no new knowledge has been learned, health care opinion leaders, decision makers, and governance organizations should be extremely reluctant to change practice guidelines. Once a new practice fills a knowledge gap, it eventually becomes the standard of care regardless of whether it is grounded in science.
Still, until additional research can be completed, policies need to be developed and implemented in an effort to respond to the evolving influenza pandemic. Although the number of casualties has been relatively low thus far,2 the characteristics of the virus could change enough to make the novel H1N1 pandemic manifestations considerably worse, perhaps as severe as the 1918–1919 pandemic.78
Ethical principles pertaining to scarce resources may serve as a framework for decision making. As previously described, permitting N95 respirators to become the standard of care without scientific justification could lead to considerable and unnecessary financial expenditures. Moreover, this approach would essentially guarantee an instantaneous global shortage of respiratory protective equipment and the conclusion that public health and emergency planners were “caught short” by an actual event. The confluence of so many challenges makes it likely that rationing of respirators during the 2009–2010 pandemic will be necessary.19
The fundamental ethical principle of justice underlies the global shortages of respiratory equipment during a pandemic and can be used to guide decision making. Justice holds that a proper solution would be one that is fair and protects people’s rights by finding a solution that will harm the least number of people.Reference Beauchamp and Childress79 One potential solution to the scarcity of respirators during the current pandemic would be to purchase and stockpile a sufficient number of respirators to the extent that rationing becomes unnecessary, even in the most severe or prolonged pandemic; however, this action invokes the principle of justice as well, wherein money becomes the scarce resource. Paying to purchase and stockpile so many respirators would take considerable funding away from other activities, about which a similarly or equally compelling case can be made for funding prioritization. Taking no action is typically viewed as unsatisfactory because it could lead to many unnecessary exposures that could have been prevented by taking some definitive preparatory action. It should also be noted that widespread purchasing of enough disposable respirators to meet the demand of a 1918-like pandemic is not feasible because limited production capabilities would preclude the delivery of millions of needed respirators in the necessary timeframe.
Ultimately, the ethical principle of justice would probably call for achieving a balance between purchasing sufficient respiratory protective equipment to meet a range of pandemic severities and reserving funds to be available for other important items unrelated to pandemic preparedness. On a practical level, if airborne transmission remains a concern, 1 reasonable approach to achieve justice could be to take 2 actions: purchase reusable respirators (which are more cost effective than disposables), such as half-face elastomeric models, in lieu of disposable respirators; and purchase sufficient numbers of surgical masks (which are much less expensive than respirators) for health care workers expected to have lower risk exposures during a severe pandemic.
CONCLUSIONS
The type of respiratory protection necessary to protect health care workers, the frontline soldiers of the evolving novel H1N1pandemic, is unknown. Until definitive, comparative effectiveness clinical trials are conducted, the answer to this question will continue to remain elusive. The knowledge gap created by this unanswered question has caused substantial debate and controversy on a global scale, leading public health organizations to feel pressured into issuing decisive recommendations despite a lack of supportive data. Changes in clinical practice caused by public health guidance during such high-profile events can be expected to establish a new standard of care. Consequently, it is possible that an unforeseen gradual transition to widespread N95 use will occur, driven by community pressures instead of science, for all outbreaks of influenza and influenza-like illness. Therefore, public health organizations and other influential institutions should take care to avoid making changes to established practice standards, if possible, unless these changes are bolstered by sound scientific evidence.
Clinical trials are being designed and/or conducted at this time to answer key questions about respiratory protection effectiveness. One is a federal consortium between the Department of Veterans Affairs, CDC, NIOSH, and Johns Hopkins University. Multiple sponsors of this trial were necessary to achieve sufficient funding. In the future, it is hoped that organizations with large funding capacity will support this type of applied research. In the meantime, relying on ethical principles that have been substantiated over time may help guide public health and clinical decisions.
Authors' Disclosures
Drs Cohen and Perl have been consultants for GlaxoSmithKline. The authors report no other conflicts of interest related to the content of this article.
