A small new study—this one analyzing antibodies in infants' stool samples—provides further evidence that the breast milk of women vaccinated against COVID-19 may help protect babies who are too young to receive the vaccine, according to findings published today in the Journal of Perinatology.
Using neutralization assays, University of Florida researchers found higher levels of immunoglobulin A and G (IgA and IgG) antibodies against SARS-CoV-2 in the stool of infants of breastfeeding mothers compared with those who breastfed from unvaccinated moms. The study involved 34 mothers and 24 infants.
The study also measured and tested antibodies found in the mothers' blood plasma and breast milk soon after vaccination and about 6 months later. The investigators found that the antibodies in the plasma and milk of vaccinated women were better able to neutralize the virus than those of unvaccinated women. Antibody levels decreased at 6 months, as has been noted previously.
This study follows up on a December 2021 study that revealed significant secretion of SARS-CoV-2–specific IgA and IgG in the milk and plasma of breastfeeding women after SARS-CoV-2 vaccination, but that study did not involve infant stool sampling.
Next step: assessing protection
"Our first study showed there were SARS-CoV-2 antibodies in the breast milk, but we couldn't say if those antibodies were getting through the babies' gastrointestinal tract and possibly providing protection there," said Joseph Larkin III, PhD, senior author of today's study, in a university news release.
Commenting on the new study, coauthor Vivian Valcarce, MD, said, "The antibodies ingested through breast milk may provide a protective coating in the infants' mouths and gastrointestinal tract."
We're following the journey of the antibodies.
Josef Neu, MD, another coauthor, added, "We're following the journey of the antibodies, from the time they are produced in mom after vaccination and now through the baby's digestive system. The next question is whether those babies are less likely to get COVID-19."
The study was funded by grants from the Children's Miracle Network and The Gerber Foundation.