Interim guidance, 6 October 2021 Direct detection of SARS-CoV-2 viral proteins (antigens) in nasal swabs and other respiratory secretions using lateral flow immunoassays (also known as rapid diagnostic tests, RDTs) offers a faster and less expensive method to test for SARS-CoV-2 than the reference method, nucleic acid amplification tests (NAATs). This interim guidance offers recommendations on the priority uses of antigen-detecting rapid diagnostic tests (Ag-RDTs) in specific populations and settings, including (i) for primary case detection in symptomatic individuals suspected to be infected and asymptomatic individuals at high risk of COVID-19, (ii) for contact tracing, (iii) during outbreak investigations and (iv) to monitor trends of disease incidence in communities. Ag-RDTs meeting minimum performance requirements can be used outside of clinical and laboratory settings, including in communities, by trained operators in accordance with instructions. The guidance additionally provides recommendations on implementation, product selection and storage.