#16,548
Over the 16+ year history of this blog, we've returned repeatedly to the (often heated) debate over the relative effectiveness of different types of face masks in preventing respiratory infections, and the wisdom, or desirability, of having the public wear face coverings during a pandemic.
Given what we know now, it's hard to believe so much time was spent debating the obvious; that while some masks (i.e. N95s) are better than others (i.e. surgical or cloth) in protecting the wearer, that any mask beats no mask at all.
Even before the 2009 H1N1 pandemic we were looking at the need for better personal protection for Health Care Workers (see 2008's PPE's: How Much Is Enough?), and at the inevitable massive shortfall in PPEs we'd see during any respiratory disease pandemic (see 2009's Caught With Our Masks Down).
There were financial and supply chain incentives in declaring surgical masks `good enough' for HCWs during a pandemic, as they cost a fraction of an N95 (see 2010's Study: Efficacy of Facemasks Vs. Respirators), are easier to manufacture, and don't require a special `fitting' and training to use (see Survival Of The Fit-tested).
But there was considerable pushback on these policies during the 2009 pandemic (see Nurses Protest Lack Of PPE’s & Report: Nurses File Complaint Over Lack Of PPE). A 2011 study published in the journal Infection Control and Hospital Epidemiology found that the inadequate use of masks by healthcare workers during the opening days of the 2009 pandemic put them at greater risk of contracting the virus (and spreading it to patients).
Fortunately, the virulence of the novel 2009 H1N1 pandemic was less than originally feared. Had it carried a significantly higher mortality rate - such as we've seen with COVID - the lack of PPEs would have become a much bigger issue.
Meanwhile, the topic of mask wearing by the general public during a pandemic was either ignored, or strongly discouraged, by most western public entities (see 2013's The Great Mask Debate Revisited), often citing their `ineffectiveness' if not worn properly.
But as early as 2007 (see Any Mask In A Viral Storm?), we looked at masking options for the general public during a pandemic. In 2009's The Man In The Ironed Mask, we looked at a design - published in a 2006 CDC's EID Journal article - of a Simple Respiratory Mask' that could be made at home out of Tee shirt material.
In 2008 we saw a study published in PLoS One (see Professional and Home-Made Face Masks Reduce Exposure to Respiratory Infections among the General Population by Marianne van der Sande, Peter Teunis, Rob Sabel) that concluded:
The bottom line: Any type of general mask use is likely to decrease viral exposure and infection risk on a population level . . .
Even after the COVID outbreak began, the WHO Interim Advice On The Community, Home, Healthcare Use of Masks For nCoV2019 and the following infamous Feb 29th, 2000 tweet by the U.S. Surgeon General both sought to discourage the use of masks by the general public.
By early April of 2020 the CDC reversed their position on cloth face covers for the public (see The CDC's Cloth Face Cover Recommendations), and the WHO would follow suit a couple of months later.
Fast forward two years, and the simple truths from those early studies continue to be validated. The latest example comes from the following MMWR report.Effectiveness of Face Mask or Respirator Use in Indoor Public Settings for Prevention of SARS-CoV-2 Infection — California, February–December 2021
Early Release / February 4, 2022 / 71
Kristin L. Andrejko1,2,*; Jake M. Pry, PhD2,*; Jennifer F. Myers, MPH2; Nozomi Fukui2; Jennifer L. DeGuzman, MPH2; John Openshaw, MD2; James P. Watt, MD2; Joseph A. Lewnard, PhD1,3,4; Seema Jain, MD2; California COVID-19 Case-Control Study Team
Summary
What is already known about this topic?
Face masks or respirators (N95/KN95s) effectively filter virus-sized particles in laboratory settings. The real-world effectiveness of face coverings to prevent acquisition of SARS-CoV-2 infection has not been widely studied.
What is added by this report?
Consistent use of a face mask or respirator in indoor public settings was associated with lower odds of a positive SARS-CoV-2 test result (adjusted odds ratio = 0.44). Use of respirators with higher filtration capacity was associated with the most protection, compared with no mask use.
What are the implications for public health practice?
In addition to being up to date with recommended COVID-19 vaccinations, consistently wearing a comfortable, well-fitting face mask or respirator in indoor public settings protects against acquisition of SARS-CoV-2 infection; a respirator offers the best protection.
(SNIP)
Discussion
During February–December 2021, using a face mask or respirator in indoor public settings was associated with lower odds of acquiring SARS-CoV-2 infection, with protection being highest among those who reported wearing a face mask or respirator all of the time. Although consistent use of any face mask or respirator indoors was protective, the adjusted odds of infection were lowest among persons who reported typically wearing an N95/KN95 respirator, followed by wearing a surgical mask. These data from real-world settings reinforce the importance of consistently wearing face masks or respirators to reduce the risk of acquisition of SARS-CoV-2 infection among the general public in indoor community settings.
These findings are consistent with existing research demonstrating that face masks or respirators effectively filter viruses in laboratory settings and with ecological studies showing reductions in SARS-CoV-2 incidence associated with community-level masking requirements (6,7). While this study evaluated the protective effects of mask or respirator use in reducing the risk the wearer acquires SARS-CoV-2 infection, a previous evaluation estimated the additional benefits of masking for source control, and found that wearing face masks or respirators in the context of exposure to a person with confirmed SARS-CoV-2 infection was associated with similar reductions in risk for infection (8). Strengths of the current study include use of a clinical endpoint of SARS-CoV-2 test result, and applicability to a general population sample.
The findings in this report are subject to at least eight limitations.
- First, this study did not account for other preventive behaviors that could influence risk for acquiring infection, including adherence to physical distancing recommendations. In addition, generalizability of this study is limited to persons seeking SARS-CoV-2 testing and who were willing to participate in a telephone interview, who might otherwise exercise other protective behaviors.
- Second, this analysis relied on an aggregate estimate of self-reported face mask or respirator use across, for some participants, multiple indoor public locations. However, the study was designed to minimize recall bias by enrolling both case- and control-participants within a 48-hour window of receiving a SARS-CoV-2 test result.
- Third, small strata limited the ability to differentiate between types of cloth masks or participants who wore different types of face masks in differing settings, and also resulted in wider CIs and statistical nonsignificance for some estimates that were suggestive of a protective effect.
- Fourth, estimates do not account for face mask or respirator fit or the correctness of face mask or respirator wearing; assessing the effectiveness of face mask or respirator use under real-world conditions is nonetheless important for developing policy.
- Fifth, data collection occurred before the expansion of the SARS-CoV-2 B.1.1.529 (Omicron) variant, which is more transmissible than earlier variants.
- Sixth, face mask or respirator use was self-reported, which could introduce social desirability bias. Seventh, small strata limited the ability to account for reasons for testing in the adjusted analysis, which may be correlated with face mask or respirator use.
- Finally, this analysis does not account for potential differences in the intensity of exposures, which could vary by duration, ventilation system, and activity in each of the various indoor public settings visited.
The findings of this report reinforce that in addition to being up to date with recommended COVID-19 vaccinations, consistently wearing face masks or respirators while in indoor public settings protects against the acquisition of SARS-CoV-2 infection (9,10). This highlights the importance of improving access to high-quality masks to ensure access is not a barrier to use. Using a respirator offers the highest level of protection from acquisition of SARS-CoV-2 infection, although it is most important to wear a well-fitting mask or respirator that is comfortable and can be used consistently.
As we reach the 900,000 American deaths milestone during this pandemic, one can't help but wonder how many lives might have been saved if we had gone into this pandemic with enough quality face masks for everyone, and the manufacturing capacity to keep up with demand.
Its not as if we didn't know we'd need them.
But we pretended that `masks' didn't matter. That the problem was too big to solve. And we gambled that the `next pandemic' would be mild, like the H1N1 pandemic of 2009. All the while comforted by `how prepared' we were (see The Inaugural Global Health Security Index).
At least when graded on the curve.
Hopefully we'll take the lessons learned from this pandemic, and be far better prepared for the next one. But sadly, our track record in such matters hasn't been particularly good.
