At St. Luke's, we've receive many inquiries from community members and leaders around the effectiveness of masks and face coverings. There is a lot of misinformation circulating today, so it's important to review the latest scientific information. Please review our answers to the most frequently asked questions below. We include citations to the evidence-based science that informed our responses.
Click each question below for its answer:
Larger studies have also shown benefits in populations of people. A recent meta-analysis by Liang, et al estimated that masks could reduce viral infections by 80% in healthcare providers (HCP) and 47% in the community. However, they noted that studies from Asia suggest greater benefit from masks likely due to greater consistency in use compared to studies done in Western countries.[i] A meta-analysis by Chu, et al[ii] estimated a possible 85% reduction in transmission with the use of any N95, mask, or 12-16 layer cotton mask in HCP and about a 44% reduction for mask use in the community.[i] Liang M, et al. Travel Med and Infect Dis 2020 https://doi.org/10.1016/j.tmaid.2020.101751.
Finally, studies have been conducted on the effectiveness of policies or mandates around mask use. In a study of the largest health care system in Massachusetts, a leadership-mandated policy of universal masking for all health care workers (HCWs) and patients on rates of SARS-CoV-2 infection was evaluated. At the time universal masking was started (late March 2020), new infections in HCWs was increasing exponentially, reaching 21.3% of overall staff (increase of 1.2% per day). Following universal masking, positive test results began to drop after two weeks to 14.7%, and 11.5% by four weeks (about 0.5% per day). The authors rightly note that other community-wide and hospital-specific interventions (distancing, washing hands, testing, etc.) also played a role, but only after universal masking was in effect for one week did infections in HCWs start to decline.[i] And in an additional recent study, COVID-19 growth rates before and after face mask mandates were compared in 15 states and the District of Columbia, demonstrating that required mask use led to a slowdown in daily COVID-19 infections. In the first five days after a mandate, the daily growth rate slowed by 0.9% compared to before mandate. At three weeks, the daily growth rate had slowed by 2% (keeping in mind that overall infection rates were 10-15%).[i][i] Lyu, et al. Community Use of Face Masks And COVID-19: Evidence from A Natural Experiment of State Mandates in the US. Health Affairs 2020. 39;8: 1–7. doi: 10.1377/hlthaff.2020.00818
A face covering should be worn over both the mouth and nose, covering below the chin. It should have a close fit to your face, not too snug and not too loose. Before you put on your face covering, ensure it and your hands are clean. An excellent video on mask wearing is available from PBS: How Well Do Masks Work.
For masks to be effective, they must be worn consistently and correctly, fitting closely to the face, and be made of fabrics that are effective in filtering respiratory droplets made by breathing, talking and coughing. A good double-layered cloth face mask is very effective. If available, a surgical mask will achieve similar results. The most important factor is if they fit comfortably covering the nose and mouth. A covering that is not worn properly is ineffective. N95s are not necessary unless used in medical situations. Any face masks with valves, such as some N95s, are not recommended due to the ability to transmit from the carrier out through the valves, thus not protecting those around you. If you wear a valved mask, you must also wear a surgical or cloth mask to protect those around you.
In your car, no, unless there is a vulnerable person in the car with you that you do not generally have close contact with (e.g., someone you do not live with). Any time you are in public and physical distancing becomes a challenge, face coverings should be worn.
Face coverings should be washed regularly if they made of reusable materials (e.g., cloth), depending on the frequency of use. Cloth face coverings can be effectively cleaned in a washing machine on a normal setting. One-time use masks should be changed out frequently.