What is the efficacy of standard face masks compared to respirator masks in preventing COVID-type respiratory illnesses in primary care staff?

Trish Greenhalgh and Xin Hui Chan, University of Oxford
Kamlesh Khunti, University of Leicester
Quentin Durand-Moreau and Sebastian Straube, University of Alberta, Canada
Declan Devane and Elaine Toomey, Evidence Synthesis Ireland and Cochrane Ireland
Anil Adisesh, University of Toronto, and St. Michael’s Hospital, Toronto, Canada

On behalf of the Oxford COVID-19 Evidence Service Team
Centre for Evidence-Based Medicine, Nuffield Department of Primary Care Health Sciences
University of Oxford