The Delta variant of concern of severe acute respiratory syndrome coronavirus 2 is dominant worldwide. We report a case cluster caused by Delta sublineage B.1.617.2 harboring the mutation E484K in Italy during July 11-July 29, 2021. This mutation appears to affect immune response and vaccine efficacy; monitoring its appearance is urgent.
Keywords: B.1.617.2; COVID-19; E484K; Italy; SARS-CoV-2; coronavirus disease; delta variant; mutation of concern; respiratory infections; severe acute respiratory syndrome coronavirus 2; variant of concern; viruses; zoonoses.