Specific antibodies are present in breast milk after maternal mRNA vaccination

Reference

Narayanaswamy V, Pentecost BT, Schoen CN, et al. Neutralizing antibodies and cytokines in breast milk after coronavirus disease 2019 (COVID-19) mRNA vaccination. Obstet Gynecol 2022;139(2):181-191.

Synopsis

These investigators solicited breast milk samples, dried blood spot samples, and infant stool samples from lactating women through a public website. The study included serial milk samples from 30 women who were vaccinated with either of the 2 available mRNA vaccines. The samples were obtained approximately every 3 days starting before the first vaccine dose until 3 weeks after the second vaccine dose. The women ranged in age from 26 years to 46 years and their infants varied in age from 7 days to 651 days at enrollment. Women self-identified racially as White (n = 27), Black (n = 1) or Asian (n = 2). The authors provided women with all necessary supplies and with detailed instructions on how to obtain, store, and ship samples of each type. Women froze the milk until shipment and shipped it on ice. Three women reported COVID-19 illness prior to enrollment, but only one had evidence of COVID-19 antibodies before the first vaccine dose. The authors described processing of samples to detect receptor-binding domain antibodies to the COVID-19 spike protein. They used pre–COVID-19 samples from other women and infants as controls. The authors measured cytokines in the milk of 26 of the women who responded to a questionnaire about vaccine side effects. Women (n = 13) who reported any side effects had median increases in interferon-gamma by more than 20-fold after the second vaccine dose, compared with median 3-fold increase among women without side effects. Approximately one third of infant stool samples obtained 3 weeks after the second vaccine dose had a sufficient increase in spike protein IgA antibodies to be considered neutralizing. There were no differences noted in maternal or infant results based on the age of the infant.