TWiV explains why this season’s influenza vaccine is not protecting against mild to moderate disease caused by H3N2 virus, and that antibody-dependent entry of SARS-CoV-2 into monocytes is a major contributor to severe COVID-19.

TWiV reviews a leaked CDC document on virulence and spread of the delta variant, and how anti-alphavirus antibodies that do not neutralize infection can nevertheless protect mice from disease.