This is the second monthly update alert for a living rapid review on the use of masks for prevention of respiratory virus infections, including severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), in health care and community settings (1). Searches were updated from 3 July 2020 to 2 August 2020 using the same search strategies as the original review, except that inclusion was restricted to peer-reviewed studies. The update searches identified 286 citations. One study on masks for prevention of SARS-CoV-2 infection in a health care setting was added for this update (Supplement Tables 1 to 3) (2); the original review and prior update had no studies on masks for prevention of SARS-CoV-2 infection.The new case–control study was done in India. It evaluated 378 health care workers infected with SARS-CoV-2 and 373 uninfected health care worker controls using data drawn from a national database registry of health care workers undergoing SARS-CoV-2 testing (2). The study found that any mask use (mask type not specified) was associated with a lower risk for SARS-CoV-2 infection compared with no mask use (unadjusted odds ratio, 0.35 [95% CI, 0.22 to 0.57]). However, mask use was not retained in the multivariable model. The study was susceptible to recall bias. In addition, 40% of eligible cases were not included in the study and attrition was not reported. Given these limitations, the strength of evidence on mask use versus no use in health care settings and risk for SARS-CoV-2 infection was assessed as insufficient (Supplement Table 4).No new studies evaluated the effects of mask use and risk for SARS-CoV-2 infection in community settings or the effects of mask use and risk for SARS-CoV-1 infection, Middle East respiratory syndrome-CoV infection, or influenza or influenza-like illness. There were no new studies on the effectiveness and safety of mask reuse or extended use. We plan the next update in 2 months.Click here for additional data file.