On Jul. 14, 2020, in an editorial published in the Journal of the American Medical Association (JAMA), the CDC reviewed the latest science and affirmed that cloth face coverings are a critical tool in the fight against COVID-19 that could reduce the spread of the disease, particularly when used universally within communities.

This review included two case studies out today, one from JAMA, showing that adherence to universal masking policies reduced SARS-CoV-2 transmission within a Boston hospital system, and one from CDC’s Morbidity and Mortality Weekly Report (MMWR), showing that wearing a mask prevented the spread of infection from two hair stylists to their customers in Missouri.

Additional data in today’s MMWR showed that immediately after the White House Coronavirus Task Force and CDC advised Americans to wear cloth face coverings when leaving home, the proportion of U.S. adults who chose to do so increased, with 3 in 4 reporting they had adopted the recommendation in a national internet survey.

The results of the Missouri case study provide further evidence on the benefits of wearing a cloth face covering. The investigation focused on two hair stylists — infected with and having symptoms of COVID-19 — whose salon policy followed a local ordinance requiring cloth face coverings for all employees and patrons. The investigators found that none of the stylists’ 139 clients or secondary contacts became ill, and all 67 clients who volunteered to be tested showed no sign of infection.

The finding adds to a growing body of evidence that cloth face coverings provide source control – that is, they help prevent the person wearing the mask from spreading COVID-19 to others. The main protection individuals gain from masking occurs when others in their communities also wear face coverings.