A new study led by the University of Massachusetts Amherst has found that women who are vaccinated against COVID-19 can transfer SARS-CoV-2 antibodies to their breastfed infants, potentially giving these babies protection against coronavirus infections.
The researchers enrolled 30 lactating women from across the United States (mostly healthcare workers) who received an mRNA vaccine between January and April 2021. They were asked to provide breast milk samples before vaccination, two to three weeks after their first vaccine dose, and three weeks after their second dose. They also provided blood samples 19 days after the first dose, and 21 days after the second dose, and infant stool samples that were collected 21 days after the mothers’ second vaccination.
The scientists found antibodies capable of neutralizing the spike protein of the original SARS-CoV-2 virus, as well as four variants, in the mothers’ milk samples and in over 30 percent of infant stool samples. The antibodies were detected in infants regardless their age (from 1.5 to 23 months old), and the levels of antibodies from the stool samples correlated with the vaccine side effects that the mothers experienced.
“Women who did feel sick from the vaccine were associated with greater antibodies in the infant stool,” said study senior author Kathleen Arcaro, a professor of Environmental Toxicology at UMass Amherst. “So you might have felt badly, but that was a benefit for your infant.”
“This research is the first to detect SARS-CoV-2 antibodies in stool samples from infants of vaccinated mothers,” explained study lead author Vignesh Narayanaswamy, a doctoral candidate in Professor Arcaro’s lab. “This is really important because women want to know whether their babies have these antibodies, and our study shows that antibodies are being transferred via breast milk. Providing this compelling evidence is motivation for women to continue breastfeeding after they receive the vaccine.”
The study is published in the journal Obstetrics and Gynecology.