Emergency use authorization for sotrovimab has been withdrawn in the US because of its poor activity against some Omicron strains of SARS- CoV-2. Sotrovimab is a monoclonal antibody directed against the SARS-CoV-2 virus that causes COVID-19. No information is available on the clinical use of sotrovimab during breastfeeding. Because sotrovimab is a large protein molecule, the amount in milk is likely to be very low. It is also likely to be partially destroyed in the infant's gastrointestinal tract and absorption by the infant is probably minimal. Similar anti-SARS-CoV-2 monoclonal antibodies were used during pregnancy and lactation in one mother with no adverse consequences. Until more data become available, sotrovimab should be used with caution during breastfeeding, especially while nursing a newborn or preterm infant.