Varela 2022.

Methods	Open‐label non‐inferiority randomised controlled trial
Participants	Study was conducted in Colombia  Inclusion criteria: people aged > 18 years of both genders and who: (a) lived in a geographic area with active COVID‐19 transmission and in areas with medium, medium‐high, and high vulnerability index; and  (b) worked outside their homes for at least 2 days during the last week. Exclusion criteria: retirement, unemployment, home‐based working, history of laboratory‐confirmed COVID‐19, working in health care, and daily N95 mask or face shield use. In addition, during follow‐up if participants reported an occupation change from work outside the home to home‐based work, or became unemployed
Interventions	Intervention group (IG): instructed to wear closed face shields with surgical face masks Active control group (ACG):  instructed to wear only surgical face mask PPE was sent to their home address for each day of participation All participants received a follow‐up twice a week by phone All participants received recorded educational intervention via email or phone that provided recommendations about COVID‐19 prevention measures, guidance to ensure adherence, and appropriate handling of the assigned PPE. Weekly short questionnaire was performed on days 7, 14, and 21 to evaluate health status SARS‐CoV‐2 symptoms, PPE use, and adherence.
Outcomes	Primary outcome was the composite result of positive RT‐PCR or seroconversion during follow‐up Secondary outcomes including PPE use and adherence
Notes	Study was nested within an observational study (CoVIDA project). Funding was provided by donors administered by the philanthropy department at the Universidad de Los Andes, external financing from the United Nations Development Programme (UNDP), and donations of diagnostic material from the Engineering Services Laboratory S.A.S. (LABSERVING S.A.S. Colombia). Funders had no input on the study at any stage. Provided analysis as ITT and PP. Missing data were imputed with negative results.

ARI: acute respiratory infection
h: hours
ITT:  intention‐to‐treat
NCT: trial register number
PPE:  personal protective equipment
PP: per protocol
RADT: rapid antigen detection test
RT‐PCR: reverse‐transcriptase polymerase chain reaction