Passive transfer of COVID-19 immunoglobulin via breast milk post COVID-19 vaccination of lactating mother: case report and review of the literature.

Infant response against infections depends largely on active and passive transfer of immunity through breast milk. There is plenty of data showing transplacental transfer of anti-severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) antibodies to the foetus and the presence of neutralising Ig-A and Ig-G anti-SARS-CoV-2 antibodies in the breast milk of mothers post COVID-19 vaccination. There is a paucity of research regarding the impact of COVID-19 vaccination of lactating mothers on the immune response in infant blood. The index case was delivered at 35 weeks of gestation with features of hydrops fetalis. The COVID-19 rapid antigen test and COVID-19 reverse transcription-polymerase chain reaction test were negative for the mother and neonate. The baby was investigated for sepsis, underwent double volume exchange transfusion, and was discharged on exclusive breastfeeding. SARS-CoV-2 antibody titres were tested in blood and breast milk samples 4 weeks after first and second dose of the COVID-19 vaccination of the mother. Growth, neurodevelopment and haematological parameters were monitored over time. A robust immune response was reported in the blood of infants post COVID-19 vaccination of the mother with the potential to confer passive immunity to the baby and without any serious side effects in the mother-infant dyad.