YES … Cloth Masks Work Against ANY Virus

I have spent a fair amount of time here demonstrating that face masks are effective against COVID-19. I have based that claim on various studies and the flow dynamics of aerosols, or the Physics of it all. It is my opinion that said research and Physics are sufficient to warrant compliance with recommendations for universal mask wearing. However, there are those who claim that without Randomized Clinical Trials (RCT’s) and meta-analyses we are foolish to proceed with adoption of masks as effective mitigation even though the massive amounts of literature attesting to that fact have existed for decades.

So … here are 7 RCT’s or meta-analyses demonstrating in varying degrees that masks are effective. It is a mixed bag of masks though, as medical masks versus cloth masks deserve distinction. The URL links are also the title of the paper, followed by some cut & paste from said papers, followed a brief summary by me in BOLD ALL CAPS ITALICS. Not yelling though.

BTW … the claim that masks work is specific to source control.


A cluster randomized clinical trial comparing fit‐tested and non‐fit‐tested N95 respirators to medical masks to prevent respiratory virus infection in health care workers

Findings  The rates of CRI (3·9% versus 6·7%), ILI (0·3% versus 0·6%), laboratory‐confirmed respiratory virus (1·4% versus 2·6%) and influenza (0·3% versus 1%) infection were consistently lower for the N95 group compared to medical masks. By intention‐to‐treat analysis, when P values were adjusted for clustering, non‐fit‐tested N95 respirators were significantly more protective than medical masks against CRI, but no other outcomes were significant. The rates of all outcomes were higher in the convenience no‐mask group compared to the intervention arms. There was no significant difference in outcomes between the N95 arms with and without fit testing. Rates of fit test failure were low. In a post hoc analysis adjusted for potential confounders, N95 masks and hospital level were significant, but medical masks, vaccination, handwashing and high‐risk procedures were not.

Interpretation  Rates of infection in the medical mask group were double that in the N95 group. A benefit of respirators is suggested but would need to be confirmed by a larger trial, as this study may have been underpowered. The finding on fit testing is specific to the type of respirator used in the study and cannot be generalized to other respirators.

YES, THE RATES WERE DOUBLE, BUT THEY WERE ALSO SMALL. 3.9% vs. 6.7%, 0.3% vs. 0.6%, etc.


A Randomized Clinical Trial of Three Options for N95 Respirators and Medical Masks in Health Workers

The rate of CRI was highest in the medical mask arm (98 of 572; 17%); followed by the targeted N95 arm (61 of 516; 11.8%); and lowest in the N95 arm (42 of 581; 7.2%) (P < 0.05). There were six laboratory-confirmed cases of influenza: four A(H1N1)pdm09 and two influenza B. Other respiratory viruses were identified in 43 subjects, the most frequent being respiratory syncytial virus (n = 17). Rates of laboratory-confirmed respiratory virus infections were low and not significant between arms: the medical mask arm (19 of 572; 3.3%); targeted N95 arm (17 of 516; 3.3%); and N95 arm (13 of 581; 2.2%) (P = 0.44). Table 2 shows that the rates of detection of bacterial pathogens in subjects with CRI were highest in the medical mask arm (84 of 572; 14.7%); followed by the targeted N95 arm (52 of 516; 10.1%); and lowest in the N95 arm (36 of 581; 6.2%) (P = 0.02). 

AGAIN, MASKS DO NOT DO AS WELL AS N95, BUT THE DIFFERENCES ARE STILL SMALL. MASKS WERE STILL EFFECTIVE.


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

Question  Is the use of N95 respirators or medical masks more effective in preventing influenza infection among outpatient health care personnel in close contact with patients with suspected respiratory illness?

Findings  In this pragmatic, cluster randomized clinical trial involving 2862 health care personnel, there was no significant difference in the incidence of laboratory-confirmed influenza among health care personnel with the use of N95 respirators (8.2%) vs medical masks (7.2%).

Meaning  As worn by health care personnel in this trial, use of N95 respirators, compared with medical masks, in the outpatient setting resulted in no significant difference in the rates of laboratory-confirmed influenza.

THE EFFICACY OF MASKS EQUALS THE EFFICACY OF N95


A cluster randomised trial of cloth masks compared with medical masks in healthcare workers

Results

The rates of all infection outcomes were highest in the cloth mask arm, with the rate of ILI statistically significantly higher in the cloth mask arm (relative risk (RR)=13.00, 95% CI 1.69 to 100.07) compared with the medical mask arm. Cloth masks also had significantly higher rates of ILI compared with the control arm. An analysis by mask use showed ILI (RR=6.64, 95% CI 1.45 to 28.65) and laboratory-confirmed virus (RR=1.72, 95% CI 1.01 to 2.94) were significantly higher in the cloth masks group compared with the medical masks group. Penetration of cloth masks by particles was almost 97% and medical masks 44%.

Conclusions

This study is the first RCT of cloth masks, and the results caution against the use of cloth masks. This is an important finding to inform occupational health and safety. Moisture retention, reuse of cloth masks and poor filtration may result in increased risk of infection. Further research is needed to inform the widespread use of cloth masks globally. However, as a precautionary measure, cloth masks should not be recommended for HCWs, particularly in high-risk situations, and guidelines need to be updated.

CLOTH MASKS LOSE BIG TIME IN THIS STUDY, BUT IT IS UNCLEAR WHETHER OR NOT THE COTTON MASKS WERE OF SUFFICIENT THREAD COUNT TO MAKE A DIFFERENCE. HYGIENE OF THE MASK AS A FACTOR IS AN IMPORTANT DISTINCTION


Effectiveness of N95 respirators versus surgical masks in protecting health care workers from acute respiratory infection: a systematic review and meta-analysis

Results:

We identified 6 clinical studies (3 RCTs, 1 cohort study and 2 case–control studies) and 23 surrogate exposure 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 (RCTs: odds ratio [OR] 0.89, 95% confidence interval [CI] 0.64–1.24; cohort study: OR 0.43, 95% CI 0.03–6.41; case–control studies: OR 0.91, 95% CI 0.25–3.36); (b) influenza-like illness (RCTs: OR 0.51, 95% CI 0.19–1.41); or (c) reported workplace absenteeism (RCT: OR 0.92, 95% CI 0.57–1.50). In the surrogate exposure studies, N95 respirators were associated with less filter penetration, less face-seal leakage and less total inward leakage under laboratory experimental conditions, compared with surgical masks.

Interpretation:

Although N95 respirators appeared to have a protective advantage over surgical masks in laboratory settings, our meta-analysis showed that there were insufficient data to determine definitively whether N95 respirators are superior to surgical masks in protecting health care workers against transmissible acute respiratory infections in clinical settings.

THE EFFICACY OF MASKS EQUALS THE EFFICACY OF N95


Effectiveness of Masks and Respirators Against Respiratory Infections in Healthcare Workers: A Systematic Review and Meta-Analysis 

Conclusions

In this review and meta-analysis, we analysed the collective evidence from published RCTs and observational studies in order to identify major gaps and methodological shortcomings in the current literature and develop evidence-based recommendations for the use of masks and respirators in healthcare settings. We found evidence to support universal medical mask use in hospital settings as part of infection control measures to reduce the risk of CRI and ILI among HCWs. Overall, N95 respirators may convey greater protection, but universal use throughout a work shift is likely to be less acceptable due to greater discomfort.

Our analysis confirms the effectiveness of medical masks and respirators against SARS. Disposable, cotton, or paper masks are not recommended.

IT IS UNCLEAR WHETHER OR NOT THE COTTON MASKS WERE OF SUFFICIENT THREAD COUNT TO MAKE A DIFFERENCE


Efficacy of face mask in preventing respiratory virus transmission: A systematic review and meta-analysis

Results

A total of 21 studies met our inclusion criteria. Meta-analyses suggest that mask use provided a significant protective effect (OR = 0.35 and 95% CI = 0.24–0.51). Use of masks by healthcare workers (HCWs) and non-healthcare workers (Non-HCWs) can reduce the risk of respiratory virus infection by 80% (OR = 0.20, 95% CI = 0.11–0.37) and 47% (OR = 0.53, 95% CI = 0.36–0.79). The protective effect of wearing masks in Asia (OR = 0.31) appeared to be higher than that of Western countries (OR = 0.45). Masks had a protective effect against influenza viruses (OR = 0.55), SARS (OR = 0.26), and SARS-CoV-2 (OR = 0.04). In the subgroups based on different study designs, protective effects of wearing mask were significant in cluster randomized trials and observational studies.

Conclusions

This study adds additional evidence of the enhanced protective value of masks, we stress that the use masks serve as an adjunctive method regarding the COVID-19 outbreak.

USE OF MASKS CAN REDUCE RISK OF RESPIRATORY INFECTION BY 80%

2 thoughts on “YES … Cloth Masks Work Against ANY Virus

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