Summary of Evidence for Use of Homemade Masks During Viral Respiratory Epidemic to Decrease Transmission among Healthcare Workers

Several studies have been published in the last 10 years evaluating the efficacy of homemade or cloth masks to prevent transmission of viral infections to healthcare workers. During the current COVID 19 epidemic, the CDC released guidance for healthcare professionals for personal protective requirements (PPE). N-95 respirators have the highest level of protection against microparticles, blocking >95% of respiratory viral pathogens, and are recommended for healthcare personnel that interface with COVID 19 when there exists the potential for respiratory aerosolization, such as intubation or bronchoscopy (https://www.cdc.gov/coronavirus/2019-nCoV/hcp/index.html). Surgical and other disposable masks are considered the second choice and can provide excellent protection against transmission of respiratory viral infection as demonstrated in a study from Vietnam published in 2015 (1). Unfortunately, supplies of PPE, including masks, may be low during the COVID 19 epidemic. Therefore, there is considerable interest in using cloth or homemade masks, particularly as respiratory viral infection risk has been found to be similar between healthcare workers considered to be in low or high-risk groups (2).

Prospective use of cloth masks as compared to use of no mask has not been studied as “it would be unethical to ask participants” in a healthcare setting during a respiratory viral epidemic to not wear a mask; in a 2015 clustered randomized prospective trial, cloth masks were inferior to surgical masks, which is to be expected (1). There are earlier data supporting the use of cloth masks when standard masks are not available. A 2008 study demonstrated that good use of cloth respiratory masks by healthcare workers decreased the risk of respiratory viral transmission (OR 0.6, CI 0.37-0.98) (3). A study of volunteers in a simulated situation in 2008 using aerosolized materials came to the conclusion that “any type of general mask use is likely to decrease viral exposure and infection risk on a population level, in spite of imperfect fit and imperfect adherence, personal respirators providing most protection. Masks worn by patients may not offer as great a degree of protection against aerosol transmission”. In this study, the use of towels, t-shirts and sweatshirts provided some limited protection against microparticles, though still far less than N-95 masks (3). The CDC suggest cloth or homemade masks may be used when other options are not available (https://www.cdc.gov/coronavirus/2019-ncov/hcp/ppe-strategy/face-masks.html, accessed 3/20/20).

In the face of medical mask shortages, this project is designed to provide a degree of respiratory protection for ALL healthcare workers, acknowledging that commercial masks provided by healthcare facilities is likely a superior option. Homemade masks cannot technically be considered PPE as their efficacy is unknown.

Optimization of this project was achieved by standardizing the following:

  1. Material choice  - dense weave, 100% cotton or cotton poly blend, doubled fabric (4), single or 2 ply heavy sterilization wrap for autoclaving can achieve filtration efficiency comparable to commonly used FDA cleared surgical masks and dust masks (5).
  2. Proper fit - standardized size with nose wire and adjustable ties for reduced leakage around the face (4).
  3. Consideration of Compliance - Something that will be worn as it is comfortable and breathable (4).

Masks can be laundered by health care facilities using best practices to improve cleanliness at least daily, sooner if visibly soiled (1).

(1) A cluster randomised trial of cloth masks compared with medical masks in healthcare workers. MacIntyre CR1, Seale H1, Dung TC2, Hien NT2, Nga PT2, Chughtai AA1, Rahman B1, Dwyer DE3, Wang Q4.BMJ Open. 2015 Apr 22;5(4):e006577. doi: 10.1136/bmjopen-2014-006577. PMID: 25903751 https://bmjopen.bmj.com/content/5/4/e006577.long

(2) Mask-wearing and respiratory infection in healthcare workers in Beijing, China. Yang P, Seale H, MacIntyre CR, Zhang H, Zhang Z, Zhang Y, Wang X, Li X, Pang X, Wang Q. Braz J Infect Dis. 2011 Mar-Apr;15(2):102-8. PMID: 21503394 https://pubmed.ncbi.nlm.nih.gov/21503394/?from_single_result=21503394

(3) Professional and home-made face masks reduce exposure to respiratory infections among the general population. van der Sande M, Teunis P, Sabel R. PLoS One. 2008 Jul 9;3(7):e2618. doi: 10.1371/journal.pone.0002618. PMID: 18612429 https://pubmed.ncbi.nlm.nih.gov/18612429/?from_single_result=18612429

(4)  Testing the efficacy of homemade masks: would they protect in an influenza pandemic? Davies A, Thompson KA, Giri K, Kafatos G, Walker J, Bennett A.Disaster Med Public Health Prep. 2013 Aug;7(4):413-8. doi: 10.1017/dmp.2013.43.PMID: 24229526 https://pubmed.ncbi.nlm.nih.gov/24229526/?from_single_result=24229526

(5) Simple respiratory protection--evaluation of the filtration performance of cloth masks and common fabric materials against 20-1000 nm size particles. Rengasamy S, Eimer B, Shaffer RE.Ann Occup Hyg. 2010 Oct;54(7):789-98. doi: 10.1093/annhyg/meq044. Epub 2010 Jun 28.PMID: 20584862 https://pubmed.ncbi.nlm.nih.gov/20584862/?from_single_result=20584862

by Kelly McMullen, MD, CLC, Jillian Ciocchetti, MD, and Amber V Flora, PhD, MLS(ASCP), MB(ASCP)