TWiV revisits Brazil’s rejection of Sputnik vaccine, examines influenza transmission via the air from the nasal epithelium of ferrets, and a history of accidental releases of polioviruses and their relevance for eradication of poliomyelitis.

TWiV examines the claim by Brazil’s ANVISA that the Sputnik vaccine contains replication-competent adenovirus, and a role for the furin cleavage site in SARS-CoV-2 spike for efficient reproduction in the respiratory tract, evasion of antiviral IFITM proteins, and transmission in ferrets.