Breast milk may protect babies against COVID-19

A new study by Washington University School of Medicine suggests that breastfeeding mothers may pass protective COVID-19 antibodies to their babies through breast milk for at least 80 days following vaccination

Researchers from Washington University School of Medicine tracked the levels of COVID-19 antibodies in breast milk before a group of mothers’ received their first vaccinations and on a weekly basis for 80 days after.

Five mothers provided frozen breast milk samples after receiving the two-dose Pfizer-BioNTech coronavirus vaccine and scientists monitored levels of the immunoglobulins IgA and IgG – antibodies deployed by the immune system to fight infections in babies.

The findings confirmed that breast milk contains elevated levels of the IgA and IgG antibodies immediately following the first dose of vaccination, with both antibodies reaching immune-significant levels within 14 to 20 days of first vaccination in all participants.

First author Jeannie Kelly, MD, assistant professor of obstetrics and gynaecology, said: “Our study showed a huge boost in antibodies against the COVID-19 virus in breast milk starting two weeks after the first shot, and this response was sustained for the course of our study, which was almost three months long. The antibodies levels were still high at the end of our study, so the protection likely extends even longer.”

Study senior author Misty Good, MD, an assistant professor of pediatrics, also at Washington University, said: “Our study is limited by a small number of participants, but the findings provide encouraging news about the potential immune benefit to breastfeeding infants after vaccination. Our paper is the first that has shown COVID-19 antibodies persist in breast milk for months following the mother’s vaccination.”

Kelly added: “There is so much vaccine misinformation out there right now – really scary, misleading posts on social media that are designed to scare moms – so we felt like we needed to look at the science. We know that these types of antibodies coat babies mouths and throats and protect against disease when a baby is drinking breast milk. So, getting vaccinated while breastfeeding not only protects mom, but also could protect the baby, too, and for months.”

COVID-19 infection in pregnancy

“We do know that COVID-19 infection is more severe during pregnancy and the main benefit of vaccination is to provide protection for moms before they become really sick, which can also be dangerous to their fetus. There have now been almost 70,000 pregnant people vaccinated against COVID 19 with no evidence of harm.”

“We’re now seeing a cascade of new data that indicate maternal vaccines are also going to help protect babies — both through transfer of antibodies through the placenta during pregnancy and through the breast milk during lactation. This is information we didn’t have a few months ago and it’s really helping us better counsel our patients who are considering getting the vaccine. I’m telling my pregnant and breastfeeding moms that I strongly recommend that they get vaccinated as soon as possible”, Kelly said.

The babies of the women included in the study ranged in age from one month to 24 months old and further studies are needed to characterise the length of antibody production in breast milk and the effect on infant infection rates.

The study has been published in the American Journal of Obstetrics and Gynecology.