Mu SARS-CoV-2 variant highly resistant to neutralization by convalescent and vaccinated sera

Researchers in Japan have warned that the Mu (B.1.621) variant of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) – the agent that causes coronavirus disease 2019 (COVID-19) – appears to be highly resistant to neutralization by sera from convalescent or vaccinated individuals.