Coronavirus Technology Solutions
November 23, 2020

Time to Standardize on CATE Masks

Masks Needed to Achieve Herd Immunity

Face Mask Efficiency is Being Studied by International Team

How Many Deaths Could be Prevented by Use of CATE Masks in the U.S.

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Time to Standardize on CATE Masks

The performance differences between masks and the potential for standardization of effective masks was addressed in a November 18 article in the Los Angeles Times by Markian Hawryluk.  Here are excerpts from the article with comments by McIlvaine in italics.

In California, new guidance that requires most residents to wear face coverings in public settings leaves people the option of using T-shirts, towels or any other cloth that hides the nose and mouth.

President-elect Joe Biden reportedly is mulling a national face-covering mandate of some sort, which could not only increase mask-wearing but also better define for Americans what sort of face covering would be most protective.

If CATE masks were the standard sufficient quantities could be produced to provide herd immunity within months. The details are in a McIlvaine news release issued Friday, November 20, 2020.

“Unlike seat belts, condoms or other prevention strategies, we have not yet standardized on what we are recommending for the public,” said Dr. Monica Gandhi, an infectious disease specialist at UC San Francisco. “And that has been profoundly confusing for the American public, to have all these masks on the market.”

At least 37 states and the District of Columbia have mandated face coverings, but there’s wide variation on what qualifies. States such as Maryland and Rhode Island include bandannas or neck gaiters, while South Carolina and Michigan do not.

Cloth-mask manufacturing was nearly nonexistent in the U.S. before the pandemic, so public health officials opted early in the year to stress the importance of wearing any face covering at all rather than trying to focus on one standard. As a result, Americans are now wearing a hodgepodge of coverings, from home-sewn to commercial versions, with various levels of protection

Researchers at the National Institute for Occupational Safety and Health have found most commercially produced cloth masks block 40% to 60% of respiratory droplets, approaching the effectiveness of surgical masks.

“You can’t possibly test everything, but certainly one take-home message is that anything is better than nothing,” said William Lindsley, a biomedical engineer at the institute. “We haven’t tested anything that has not worked.”

CATE masks are already tested by Nelson Laboratories and other commercial and reliable testing companies around the world.  All that is needed is that suppliers submit their masks for performance tests, particularly Particle Filtering Efficiency and Inhalation and Exhalation Resistance. They can  bear the cost of testing. So there is no delay to wait for a government agency to do the testing. Those suppliers with efficient masks have made considerable investments in testing. So this will not delay an accelerated mask production program.

Gandhi believes it’s time to raise the standards for masks, ramp up the production of disposable surgical masks and encourage, if not order, Americans to wear them.

It is the fit as well as media efficiency. The standards should include the effectiveness which includes leaks as well as penetration.

Masks Needed to Achieve Herd Immunity

In the Alert on Friday we discussed the need for CATE masks to achieve herd immunity. We have slightly revised figures today. The number required drops to 323 million each quarter by July 2022.

The number is probably going to be greater because even people who have been vaccinated have at best 95% protection. So they will want to wear masks and may even be required to do so  during the next  two years.

Because CATE masks are tight flitting, efficient, comfortable and attractive they will be 93% effective where utilized. It was determined that only 1 mask would be needed per quarter due to reusability.

The surgical masks have high filtration efficiency but lots of leakage. The assumption is that the usage will be just one per day or 90 per quarter. To meet the needs of the world on July 1 2021 with 20% of the 6 billion active people vaccinated there would be a demand for 378 billion masks per quarter. This reduces to just under 38 billion by July of 2022. Since meltblowns are typically used in surgical masks and there is a big investment and delay in building new melt blown lines it is very unlikely that the suppliers would or could gear up for a market which will peak in the next year and then shrink substantially.

The cloth masks range in efficiency. In the example below we have selected relatively efficient designs. Many would have a 90% inefficiency rating. We have selected reusable masks in the $15-30 price range.  Even with a 51% inefficiency rating it would not be possible to achieve herd immunity with only 20% of the people vaccinated. You would need to mask 102% of the active population.

Herd immunity could be achieved by July 2022 if 10% of the active people are wearing cloth masks and 65% are protected through vaccinations. However of the 5% who are not vaccinated, probably half are in fear of side effects. These people will be ones who will want CATE masks rather than cloth masks because of the higher protection.

Because of the huge immediate needs quick herd immunity will only take place with some mix of CATE, Surgical, and Cloth masks. But it is achievable. The Biden Administration is considering a mask mandate. Many countries already have them. The problem is that without specifying effectiveness some people are wearing masks which provide almost no protection.

One way to achieve herd immunity would be to specify CATE masks for those who are at most risk and allow surgical and cloth masks for others. However, for those masks with lower effectiveness some specification must be set. It should be some combination of maximum  penetration plus leakage. Europe has some community mask specifications set around 80% efficient media. However with out fit being included the specifications are inadequate.

The requirements can be based on expected load factors. CATE masks could be required in subways and theaters. Lower efficiency levels could be allowed for walking suburban streets or in grocery stores which have HEPA filtration and laminar air flow at checkout counters. This means that people may carry several masks and use the one appropriate for the setting.

The requirements can be synchronized with the production capabilities of suppliers. If the guidelines are set appropriately, we could have herd immunity in six months and save many hundreds of thousands of lives.

Face Mask Efficiency is Being Studied by International Team

A team of researchers have tested everything from T-shirts and socks to jeans and vacuum bags to determine what type of mask material is most effective at trapping the ultrafine particles which may contain viruses such as SARS-CoV-2, the virus which causes COVID-19.  McIlvaine’s comments about their findings are shown in italics.

The researchers, from the University of Cambridge and Northwestern University, tested the effectiveness of different fabrics at filtering particles between 0.02 and 0.1 micrometers – about the size of most viruses – at high speeds, comparable to coughing or heavy breathing. They also tested N95 and surgical masks, which are more commonly used in healthcare settings.

“It’s a matter of finding the right balance – we want the materials to be effective at filtering particles, but we also need to know they don’t put users at risk of inhaling fibres or lint, which can be harmful.” — Eugenia O’Kelly

Previous studies have only looked at a small selection of fabrics when the wearer is breathing normally, when particles are expelled at lower speed. Studying more fabrics and testing them at higher speeds provides a more robust evidence base for the effectiveness of fabric masks.

The results, reported in the journal BMJ Open, show that most of the fabrics commonly used for non-clinical face masks are effective at filtering ultrafine particles. N95 masks were highly effective, although a reusable HEPA vacuum bag actually exceeded the N95 performance in some respects.

As for homemade masks, those made of multiple layers of fabric were more effective, and those which also incorporated interfacing, which is normally used to stiffen collars, showed a significant improvement in performance. However, this improvement in performance also made them more difficult to breathe through than an N95 mask.

The researchers also studied the performance of different fabrics when damp, and after they had gone through a normal washing and drying cycle. They found that the fabrics worked well while damp and worked sufficiently after one laundry cycle, however, previous studies have shown that repeated washing degrades the fabrics, and the researchers caution that masks should not be reused indefinitely.

“Fabric masks have become a new necessity for many of us since the start of the COVID-19 pandemic,” said first author Eugenia O’Kelly from Cambridge’s Department of Engineering. “In the early stages of the pandemic, when N95 masks were in extremely short supply, many sewers and makers started making their own fabric masks, meeting the demands that couldn’t be met by supply chains, or to provide a more affordable option.”

While there are numerous online resources that help people make their own masks, there is little scientific evidence on what the most suitable materials are. There is ten years of data and research on CATE masks used for air pollution protection and for those with health problems. Testing companies such as Nelson Laboratories are paid millions of dollar per year to make tests of various filter media.

“There was an initial panic around PPE and other types of face masks, and how effective they were,” said O’Kelly. “As an engineer, I wanted to learn more about them, how well different materials worked under different conditions, and what made for the most effective fit.”

For the current study, O’Kelly and her colleagues built an apparatus consisting of sections of tubing, with a fabric sample in the middle. Aerosolized particles were generated at one end of the apparatus, and their levels were measured before and after they passed through the fabric sample at a speed similar to coughing.

The researchers also tested how well each fabric performed in terms of breathing resistance, based on qualitative feedback from users. “A mask which blocks particles really well but restricts your breathing isn’t an effective mask,” said O’Kelly. “Denim, for example, was quite effective at blocking particles, but it’s difficult to breathe through, so it’s probably not a good idea to make a mask out of an old pair of jeans. N95 masks are much easier to breathe through than any fabric combinations with similar levels of filtration.”

In preparation for the study, the researchers consulted with online sewing communities to find out what types of fabric they were using to make masks. Due to the severe shortage of N95 masks at the time, several of the sewers reported that they were experimenting with inserting vacuum bags with HEPA filters into masks.

The researchers found that single-use and reusable vacuum bags were effective at blocking particles, but caution that the single-use bags should not be used in face masks, as they fall apart when cut, and may contain component materials which are unsafe to inhale.

“It’s a matter of finding the right balance – we want the materials to be effective at filtering particles, but we also need to know they don’t put users at risk of inhaling fibers or lint, which can be harmful,” said O’Kelly.

The researchers caution that their study has several limitations: namely, that they did not look at the role which fit plays in filtering particles.  McIlvaine points out that while CATE masks have only 8% leakage, many masks allow 50% of the air to move around the edges of the mask.

In a related project, O’Kelly has been studying how the fit of masks in healthcare settings can be improved. In addition, many viruses are carried on droplets which are larger than those looked at in the current study. Several CATE mask suppliers have efficient sealing techniques and offer up to five different mask sizes to insure good fit.

However, O’Kelly says the results may be useful for sewers and makers when choosing which fabric to use for making masks. “We’ve shown that in an emergency situation where N95 masks are not available, such as in the early days of this pandemic, fabric masks are surprisingly effective at filtering particles which may contain viruses, even at high speeds.”

Further information about the research can be found at: www.facemaskresearch.com

Reference: “Ability of fabric face mask materials to filter ultrafine particles at coughing velocity” by Eugenia O’Kelly, Sophia Pirog, James Ward by P John Clarkson, 22 September 2020, BMJ Open.

DOI: 10.1136/bmjopen-2020-039424

How Many Deaths Could be Prevented by Use of CATE Masks in the U.S.

The answer is subject to so many variables that precision is impossible. But we can create useful estimates.  Eric Boodman of STAT provided some insights.  Excerpts from his article are shown below with McIlvaine comments in Italics

The death forecasts keep rising. new numbers, published Friday, bolster what scientists have long been saying: That doing away with social distancing measures could entail vast numbers of deaths, and that widespread mask-wearing in public could save tens of thousands of lives.

“We think the key point here is that there’s a huge winter surge coming,” Christopher Murray, a lead author on the paper and the director of the University of Washington’s Institute for Health Metrics and Evaluation, said in a press briefing. At this point, the wave isn’t fully preventable, but “expanding mask use is one of the easy wins for the United States.”

Specifically, the paper projected that there could be some half a million Covid-19-related deaths in the U.S. by the end of February, and that some 130,000 of those tragedies might be forestalled with universal mask use. But experts warn that the figures from any of the model’s hypothetical scenarios are less useful than the comparison between the different possibilities. By putting those projections side by side, you can start to see how much of an effect something like mask-wearing might have on a population level, if you take the authors’ estimation that face coverings can reduce an individual’s risk of infection by about 40%.

This is like saying taking drugs will reduce your risk by 40%. There is as much difference in mask types as there is between a malaria drug and the new Pfizer vaccine.

“The exact numbers are impossible to predict,” said Ruth Etzioni, a biostatistician at the Fred Hutchinson Cancer Research Center and the University of Washington, who was not involved in the new research. “What should drive policy here is the difference between the scenarios with and without masks.”

The IHME team’s initial work last spring didn’t try to model transmission rates and incubation periods of the novel coronavirus, but rather tried to fit the United States onto data from outbreaks elsewhere, and showed a bell-like curve, with cases largely rising and falling symmetrically. Their projections also wobbled a fair amount, and as Nicholas Reich, a University of Massachusetts, Amherst, biostatistician whose team compares a number of different Covid-19 models, described them to STAT, “were inaccurate and did not reflect the consensus of the modeling community.”

The IHME then switched to a more traditional way of modeling infectious disease, which aims to calculate the mathematical cascade of transmission: the number of people susceptible to the disease, how many of them get exposed, how many then get infected, and how many recover and therefore have at least temporary immunity.

Once the institute made the switch, Reich explained, “their more recent short-term forecasts, which have been submitted to the COVID-19 Forecast Hub, have performed reasonably well in accuracy for up to one month into the future. They aren’t the best model, but they seem to be making reasonably accurate short-term predictions.”

This paper, however, extends beyond that one-month mark, and the further you go into the future, the greater the uncertainty of projections. The team used state-by-state data from the past on case rates and all sorts of other variables—such as cell phone mobility data, seasonal pneumonia fluctuations, levels of mask use—to then project how tweaking those variables might shift the results.

This sort of analysis is not designed to tell us how effective wearing a mask is at reducing disease spread. Rather, that is just one of many bits of information that the researchers fed into their model — and their estimate on that front comes from a meta-analysis they did of previous peer-reviewed studies and preprints that looked specifically at that question.

Nor should we expect this model to give any sort of certainty about what the future holds.

“It’s not a forecast per se, because the outcomes are conditional on very specific model assumptions about how effective masks are and how much uptake there is in wearing mask”Reich said.  Mask effectiveness is a matter of mask choice.

Instead, as Zeynep Tufekci put it in The Atlantic, we should use this sort of study for “pruning catastrophic branches of a tree of possibilities that lies before us.”

Because all sorts of policy and behavior changes took place at once, it’s nearly impossible to pick apart the influence of any one strand. What this sort of analysis can provide is a hint of the general direction we should be headed — and the ones we should avoid — to keep as many people as possible safe. Given that a scenario in which every single person wears a mask in public all the time results in many fewer deaths than one in which mask use continues at its estimated current pace, one effective course of action seems pretty clear, the authors say.  Number of hours of mask use, the viral load, mask fit, and filter efficiency are all important variables.

As unsurprising as their conclusion is, it can still be useful to say it.

“We don’t need a model to tell us that we should all be wearing masks, we don’t need a model to tell us that if we continue the way we’re going, we’re going to see tens of thousands more deaths within the next couple of months,” said Etzioni. “But sometimes when a person provides a model and you see these curves and you see these numbers, it helps appropriately freak you out.”

She added that it might also help bolster public health policy decisions: “A model like this can be very important for our governors who are actually trying to do something to enforce mask mandates. They’re not popular, so politically it can make it tough on a governor who’s trying to do the right thing. Models like this can provide a kind of evidence to support that policy.”

About the Author

Eric Boodman

General Assignment Reporter

https://www.statnews.com/2020/10/23/universal-mask-use-could-save-130000-lives-by-the-end-of-february-new-modeling-study-says/