COVID-19 Antibodies Found in Breast Milk

By Ethan Covey

Researchers found that two groups of mothers during the COVID-19 pandemic—those who had disease-acquired immunity and those with vaccine-induced immunity—had high levels of antibodies in their breast milk, and these antibodies provided neutralization of SARS-CoV-2 (JAMA Pediatr 2021 Nov 10. doi:10.1001/jamapediatrics.2021.4897).

Samples were collected 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. Mothers who had disease-acquired immunity produced high levels of immunoglobulin A (IgA) antibodies against the virus in breast milk, while vaccine-acquired immunity produced robust immunoglobulin G (IgG) antibodies.

Both antibodies provided neutralization of SARS-CoV-2, the first time such evidence has been discovered for both IgA and IgG antibodies, according to study co-author Bridget Young, PhD, an assistant professor in the Division of Pediatric Allergy and Immunology at the University of Rochester Medical Center (URMC), in New York.

“It's one thing to measure antibody concentrations, but it's another to say that antibodies are func-tional and can neutralize the SARS-CoV-2 virus,” Dr. Young said. "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.”

Previous studies from URMC had shown evidence of antibodies in breast milk from COVID-19?positive mothers. This follow-up study represents the longest time period that disease-acquired antibodies have been examined post-illness, and the results showed these antibodies persist for three months after infection.

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

“The trend in breast milk antibodies aligns with what we see in vaccination sera,” said study co-author Kirsi Jarvinen-Seppo, PhD, MD, the 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.”

Both Drs. Young and Jarvinen-Seppo emphasize, however, that although the antibody response exists, it's not yet shown whether these breast milk antibodies can provide protection against COVID-19 for nursing children.

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