COVID antibodies found in breast milk of vaccinated, previously-infected mothers

Rochester, New York— According to the University of Rochester Medical Center researchers, they found evidence that mothers with two types of immunities from COVID-19, vaccination-acquired and disease-acquired, produced breast milk with active COVID-19 antibodies.

The study collected samples from 77 mothers — 47 in the infected group, and 30 in the vaccine group — to determine the level of antibodies in breast milk over time.

According to the researchers’ study, they found mothers with disease-acquired immunity produced high levels of Immunoglobulin A (IgA) antibodies against the virus, while vaccine-acquired immunity produced robust Immunoglobulin G (IgG) antibodies. According to the study, both types of antibodies provide neutralization against COVID-19.

“It’s one thing to measure antibody concentrations, but it’s another to say that antibodies are functional and can neutralize the SARS-CoV-2 virus,” said Bridget Young, Ph.D., assistant professor in the Division of Pediatric Allergy and Immunology at URMC., “One of the exciting findings in this work is that breast milk from both mothers with COVID-19 infection, and from mothers receiving mRNA vaccination contained these active antibodies that were able to neutralize the virus.”

According to the previous studies, evidence of antibodies was found in milk from COVID-positive mothers.

This new report represents the longest time period that disease-acquired antibodies have been examined post-illness, and results show these antibodies exist for three months post-infection.

For vaccinated mothers, the study found evidence of a mild-to-modest decline in antibodies, on average, three months after vaccination.

“The trend in breast milk antibodies aligns with what we see in vaccination sera,” said study co-author Kirsi Jarvinen-Seppo, PhD, M.D., Chief of Pediatric Allergy and Immunology at URMC, “after a few months, the antibodies trend downward, but the levels are still significantly above what they were pre-vaccine.”

Researchers emphasized that while the antibody response exists, it’s not yet shown whether these breast milk antibodies can provide protection against COVID for nursing children.

“The study does not imply that children would be protected from illness,” said Jarvinen-Seppo, “and breast milk antibodies may not be a substitute for vaccination for infants and children, once approved.”