COVID-19 is spread person-to-person through close contact. To prevent virus spread, masking (wearing a mask) has emerged as an effective and simple response. Several recent studies consider how it works.
An analysis conducted by the Institute for Health Metrics and Evaluation (IHME) analytics extracted all relevant data from studies #2, 3, and 4, outlined below. Researchers also included additional factors such as population and mask type.
Their analysis of mask effectiveness for respiratory infections generally suggests a reduction in infection for mask-wearers by at least one-third compared to control groups. This work supports the growing scientific consensus that masks, whether homemade or commercial, can reduce respiratory virus infections by 33% and slow COVID-19's community spread.
A review of 172 studies from across the world was conducted by researchers and published in the scientific journal The Lancet to investigate the optimum distance for avoiding person-to-person virus transmission and to assess the use of face masks and eye protection to prevent transmission of viruses.
Results indicate that transmission of viruses was 10% lower with physical distancing of 3.28 feet or more, compared with a distance of less than 3.28 feet and protection was increased as distance was lengthened. Face mask use could result in a 14.3% further reduction in risk of infection.
Another review of 21 studies suggests that mask use provides a significant protective effect.
Use of masks by healthcare workers and non-healthcare workers can reduce the risk of respiratory virus infection by 80% and 47%. This study adds additional evidence of the enhanced protective value of masks and stresses mask use as a strong preventive method for infections during the COVID-19 outbreak.
A retrospective cohort study of 335 people in 124 families and with at least one laboratory confirmed COVID-19 case per family was conducted from February 28, 2020 to March 27, 2020 in Beijing, China.
Results indicate that face mask use by the primary case and family contacts before the primary case developed symptoms was 79% effective in reducing transmission. Wearing a mask after illness onset of the primary case was not significantly protective.
State policies mandating public or community use of masks or facial coverings were issued by 15 states and the District of Columbia between April 8 and May 15, 2020. Subsequent research examined changes in the daily county-level COVID-19 growth rates between March 31, 2020 and May 22, 2020.
Average daily county-level growth rate decreased by 0.9, 1.1, 1.4, 1.7, and 2.0 percentage-points in 1–5, 6–10, 11–15, 16–20, and 21+ days after signing, respectively.
Increasing evidence also suggests that population-wide wearing of masks may not only reduce the frequency of transmission, but also its severity.
Given the effectiveness of masks to reduce transmission by an average of 33%, widespread use of masks has the potential to change the course of the pandemic in many locations around the world, including the U.S.