Some masks better than others

Phil C. McNasty

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Cowling, B. et al. (2010) “Face masks to prevent transmission of influenza virus: A systematic review,” Epidemiology and Infection, 138(4), 449-456. None of the studies reviewed showed a benefit from wearing a mask, in either HCW or community members in households (H). See summary Tables 1 and 2 therein.

 

Phil C. McNasty

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Dec 27, 2010
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Phil C. McNasty

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Dec 27, 2010
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Smith, J.D. et al. (2016) “Effectiveness of N95 respirators versus surgical masks in protecting health care workers from acute respiratory infection: a systematic review and meta-analysis,” CMAJ Mar 2016. “We identified six clinical studies … . In the meta-analysis of the clinical studies, we found no significant difference between N95 respirators and surgical masks in associated risk of (a) laboratory-confirmed respiratory infection, (b) influenza-like illness, or (c) reported work-place absenteeism.”

 

Phil C. McNasty

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Offeddu, V. et al. (2017) “Effectiveness of Masks and Respirators Against Respiratory Infections in Healthcare Workers: A Systematic Review and Meta-Analysis,” Clinical Infectious Diseases, Volume 65, Issue 11, 1 December 2017, Pages 1934–1942. “Self-reported assessment of clinical outcomes was prone to bias. Evidence of a protective effect of masks or respirators against verified respiratory infection (VRI) was not statistically significant”; as per Fig. 2c therein:


 

Phil C. McNasty

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Radonovich, L.J. et al. (2019) “N95 Respirators vs Medical Masks for Preventing Influenza Among Health Care Personnel: A Randomized Clinical Trial,” JAMA. 2019; 322(9): 824–833. “Among 2862 randomized participants, 2371 completed the study and accounted for 5180 HCW-seasons. ... 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.”

 

Phil C. McNasty

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Long, Y. et al. (2020) “Effectiveness of N95 respirators versus surgical masks against influenza: A systematic review and meta-analysis,” J Evid Based Med. 2020; 1- 9.
“A total of six RCTs involving 9,171 participants were included. There were no statistically significant differences in preventing laboratory-confirmed influenza, laboratory-confirmed respiratory viral infections, laboratory-confirmed respiratory infection, and influenza-like illness using N95 respirators and surgical masks. Meta-analysis indicated a protective effect of N95 respirators against laboratory-confirmed bacterial colonization (RR = 0.58, 95% CI 0.43-0.78). The use of N95 respirators compared with surgical masks is not associated with a lower risk of laboratory-confirmed influenza.”

 

lenny2

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Jan 18, 2012
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I actually think wearing masks have made things worse, and our current MUCH worse 2nd wave would prove that.
"...some communities in South Dakota have chosen a different path. The city of Brookings - fourth largest in the state - was the first to impose rules on masks inside businesses in September, along with other measures.

...Brookings County now has the lowest infection rate out of the five most populous South Dakota counties.

In September when the city of Brookings introduced tighter Covid restrictions, including mask-wearing measures, it had the highest.

Also, as infections rose across the state in October and November, the upturn in Brookings was lower than elsewhere.

We can't say that this was down to masks usage alone, but Bonny Specker, an epidemiologist at South Dakota State University, says along with measures such as limits on bars and restaurants, rules on face coverings have made a difference.

"South Dakota does not have a mask mandate and has one of the highest rates per capita of current hospitalisations and deaths in the country. When you compare Brookings County to other counties that have the 10 most populous cities, the data is consistent with the mask mandate being helpful."

...Governor Noem has pointed to other US states which have had mask mandates in place for some time but are still seeing cases rise.

Her spokesman, Ian Fury, has said: "Look at Minnesota, Wisconsin, and Illinois - states that have had mask mandates for months but are still seeing rapidly increasing cases."

It's true that these states have experienced an increase, but none has seen as many cases per capita throughout the pandemic as South Dakota, nor such a dramatic peak in November.

After introducing mask mandates along with other Covid restrictions, Minnesota, Illinois and Wisconsin kept cases relatively low, but they have seen a spike as infections have risen across the US since the summer.

All three states have implemented tighter restrictions throughout the pandemic than South Dakota alongside mask mandates, and their recent surges have been later and less severe.

Since the start of the outbreak, South Dakota has had more than 9,700 total cases per 100,000 people, compared with around 7,600 in Wisconsin, and 6,300 in Illinois and Minnesota.

"Studies out of the US suggest requiring masks in public can help to reduce infection rates.

A study by the US Centers for Disease Control (CDC) released in late November looked at infection rates in Kansas from June to August.

In the summer, the state's governor introduced compulsory mask-wearing in public spaces but allowed local counties to opt out, and most chose to.

The study found that cases decreased in parts of Kansas which had brought in rules on wearing a mask, but cases continued to rise in those that chose not to.

It said these findings were "consistent with declines in Covid-19 cases observed in 15 states and the District of Columbia, which mandated masks, compared with states that did not have mask mandates."

Assistant professor Kate Grabowski, who reviews research papers at Johns Hopkins University, says: "All of the studies we have reviewed show that mask mandates are effective."

 

shack

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Okay you wanna see studies, here's a whole bunch of them.

First read this. Its basic science. And EXACTLY what I've been saying all along:


A basic understanding of how masks work helps. Masks are filters. The material used in a standard surgical mask (by far the more common type of mask) reduces transmission of bacteria. Both bacteria and viruses are microscopic microbes, but they differ greatly. Bacteria are living cells, while a virus is a particle that requires a host cell to replicate. A coronavirus virion (particle) is spherical, averaging around 125 nanometers in diameter. Compare that to bacteria’s 1,000-nm size. It’s a grape compared to a grapefruit. A surgical mask whose purpose is to block bacteria will do little to prevent passage of the smaller coronavirus particle. That’s why N95 masks, which block 95% of all airborne particles, are the gold standard in hospitals treating COVID-19 patients. They have a much more selective filter.
1)This fails to acknowledge that the virus is contained in droplets as it exits the respiratory system. These droplets are approx. 1 micron (1,000 nanometers) in diameter and masks can filter down to 0.3 microns. They will block at least some of the virus. There is some protection.

2)There is no comparison of 2 groups, one wearing masks and one not, both exposed to the same environment and see what, if any, difference there is.

As such there are too many variables at play other than just mask wearing. This study PROVES nothing.
 
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shack

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Jacobs, J. L. et al. (2009) “Use of surgical face masks to reduce the incidence of the common cold among health care workers in Japan: A randomized controlled trial,” American Journal of Infection Control, Volume 37, Issue 5, 417 – 419. N95-masked health-care workers (HCW) were significantly more likely to experience headaches. Face mask use in HCW was not demonstrated to provide benefit in terms of cold symptoms or getting colds:
1)77 people in total is an extremely small sample size, less than 40 each. Actually, it is too small to be considered statistically conclusive or relevant.
2)It does not say how faithful the mask wearers had to be. Did they wear it 24/7? Was it at their discretion? No details were provided.
3)When was it conducted? Was it in the summer when colds are not very prevalent? It does not say.
4)Even if in winter, what is the prevalence of people who have colds compared to the current prevalence of covid virus? It does not say.
5)Mask wearing is already very prevalent in Japan so the prevalence of cold cases would be less than the prevalence of covid currently occurring.
6)Comparing cold to covid may not be valid as the mode or ease of transmission may be different. It does not say.

Doing two separate groups is good but the the sample size is waaay too small and there are too many relevant details omitted to be able to draw any conclusions. This study PROVES nothing.
 
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shack

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Cowling, B. et al. (2010) “Face masks to prevent transmission of influenza virus: A systematic review,” Epidemiology and Infection, 138(4), 449-456. None of the studies reviewed showed a benefit from wearing a mask, in either HCW or community members in households (H). See summary Tables 1 and 2 therein.

From the study:
There is some evidence to support the wearing of masks or respirators during illness to protect others, and public health emphasis on mask wearing during illness may help to reduce influenza virus transmission. There are fewer data to support the use of masks or respirators to prevent becoming infected. Further studies in controlled settings and studies of natural infections in healthcare and community settings are required to better define the effectiveness of face masks and respirators in preventing influenza virus transmission.

This says:
1)Masks help to decrease transmission. There IS a benefit to wearing a mask.
2)The results of this study, which dealt with whether there would be a difference in prevention to an individual wearing a mask, is inconclusive. It PROVES nothing in this regard.

I'll get to the rest of the studies later but so far it is like shooting fish in a barrel.

BTW, appreciate your efforts searching out studies as I'd requested.
 
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Phil C. McNasty

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1)This fails to acknowledge that the virus is contained in droplets as it exits the respiratory system. These droplets are approx. 1 micron (1,000 nanometers) in diameter and masks can filter down to 0.3 microns. They will block at least some of the virus. There is some protection
Against droplets yes, but Covid-19 is airborne as I've said many times, and it can exist in microscopic amounts in exhaled air.
And as that link suggests, most masks people are wearing nowadays contain many gaps from which contaminated air can escape from.

Conclusion = most masks are useless, and the current MUCH worse 2nd waves Ontario, Spain, France, Italy, NL, Denmark, Germany....etc are experiencing would support that hypothesis
 

lenny2

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Flu infections are lower this year than previous years due to the extreme safety measures.

C-19 has no previous years to compare it with since it is a new virus. But it's obvious that without extreme safety measures the number of infections would be much higher. Relative to a 2020 without such measures, the number of C-19 infections in 2020 are very low.

BTW, C-19 is a much more infectious disease than the flu.
 

shack

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Against droplets yes, but Covid-19 is airborne as I've said many times,
But it is not airborne as an independent entity. They are always in a droplet and it is the droplet which is airborn. therefor the diameter of the droplet is what is important. Masks filter down to 0.3 microns and the droplets are 1.0 microns or more.
 
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Phil C. McNasty

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But it is not airborne as an independent entity. They are always in a droplet and it is the droplet which is airborn. therefor the diameter of the droplet is what is important. Masks filter down to 0.3 microns and the droplets are 1.0 microns or more.
False! Coronavirus can be transmitted through air as well, not just droplets
 

shack

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False! Coronavirus can be transmitted through air as well, not just droplets
How? There are droplets/moisture in every breath we exhale and the virus is in them.
 

shack

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DUH......exactly my point!
Double d'uh.

Those droplets that contain the virions are bigger than the pores in the mask by at least 3X. The masks will stop a lot of the virions because they are not free but encased in the droplets.

Exactly my point and totally disproves yours. Masks make a difference.
 
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