Background: In May and June 2020 many Black Lives Matter (BLM) protests occurred around the world. We aimed to estimate the use of masks during protests and analyze the temporal relationship of protests to COVID-19 epidemiology.Methods: Twelve cities which had BLM protests and met inclusion criteria were selected. Two reviewers screened 496 protest images for mask use, with high inter-rater reliability. Protest intensity, use of tear gas, government control measures and testing rates were estimated for each city. A correlation analysis was conducted to assess the potential effect of mask use and other measures, adjusting for testing rates, on COVID-19 epidemiology four weeks (two incubation periods) post-protests.Findings: Mask use ranged from 69-96% across protests. There was no increase in incidence of COVID-19 post-protest in 11 of the 12 cities studied. After adjusting for testing rates, only Miami, which involved use of tear gas and had high protest intensity, showed a clear increase in COVID-19 after one incubation period post-protest. No significant correlation was found between incidence and protest factors.Interpretation: Despite the concerns that protests may increase COVID-19 transmission, protests in most cities studied did not increase COVID-19 incidence, and most protesters wore masks. The absence of an epidemic surge within two incubation periods of a protest is indicative that the protests did not have a major influence on epidemic activity, except in Miami. Outdoor mass gathering with high levels of mask use may not pose as high a risk for COVID-19 as indoor gatherings.Funding Statement: This research did not receive any specific grant from funding agencies in the public, commercial, or not-for-profit sectors.Declaration of Interests: The author certifies that they have NO affiliations with or involvement in any organization or entity with any financial interest (such as honoraria;educational grants;participation in speakers’ bureaus;membership, employment, consultancies, stock ownership, or other equity interest;and expert testimony or patent-licensing arrangements), or non-financial interest (such as personal or professional relationships, affiliations, knowledge or beliefs) in the subject matter or materials discussed in this manuscript.Ethics Approval Statement: Data used for this study was publicly available and deidentified. No ethical approval was required.
Estimated Mask Use and Temporal Relationship to COVID-19 Epidemiology of Black Lives Matter Protests in 12 Cities