Vaccinated breastfeeding mothers pass on protective antibodies to their infants
Human breast milk is a rich cocktail of proteins, fat, carbohydrates and biologically active factors that shield vulnerable infants from infections and establish a healthy immune system and gut microbiome.
Early reports during the pandemic suggested that children and babies were less prone to severe, life-threatening forms of COVID. Most kids infected by the coronavirus don’t become as sick as adults, often not even displaying any symptoms at all.
However, the statistics are staggering — over a million children in the U.S. have been diagnosed with COVID. Of these, babies under the age of one are in the high-risk category due to their smaller airways and immature immune systems. Early recommendations advised caregivers to wear masks around newborns and even to socially distance from babies where possible.
But what about COVID-positive mothers? Could their breast milk transmit the coronavirus to their nursing babies?
“We only want to sequester a mother from her baby if it’s medically necessary.”
Keep babies and mothers together
Quite the opposite, says University of Rochester scientists. Their study found that breast milk samples from mothers with COVID-19 found didn’t contain the coronavirus, instead being a rich source of protective antibodies, some of which could neutralize SARS-CoV-2.
Samples from 37 mothers (18 of which were COVID-positive) were used in the study, with around two-thirds of them containing the beneficial antibodies. These data provide much-needed guidance for physicians deciding whether COVID-positive mothers need to be isolated from their newborn babies — a move initially regarded as best practice at the beginning of the pandemic.
“We only want to sequester a mother from her baby if it’s medically necessary,” said one of the study authors, Bridget Young.
“However, the issue was very confusing for practitioners who don’t have sufficient evidence. These early results suggest that breast milk from mothers who have had a COVID-19 infection contains specific and active antibodies against the virus, and that they do not transfer the virus through milk. This is great news!”
Microbiologists and immunologists led by Mark Sangster and David Topham, set about quantifying breast milk antibody levels using assays developed in their laboratories.
“We found high levels of IgA — a common antibody in blood and other body fluids — in their breast milk. IgA’s migrate in mucosal transfer, therefore this is encouraging information that mothers transfer these antibodies,” Sangster says.
“In addition, 62% of the milk samples were able to neutralize SARS-CoV-2 infectivity in vitro, whereas milk samples collected prior to the COVID-19 pandemic were unable to do so,” wrote the authors, demonstrating that the antibodies in breast milk were functional and protective for babies.
This preliminary study provides some clarity around how breastfeeding can help protect vulnerable newborns from COVID-19 infections. Ongoing studies are validating the results obtained in a larger cohort of mothers, with the aim of tracking their immunological secretions for two months.
“This work needs to be replicated in larger cohorts. Additionally, we now need to understand if the COVID-19 vaccine impacts breast milk in the same way,” Young said.
COVID vaccines enhance the immune benefits of breastmilk
How does getting a COVID shot change the composition of breastmilk? According to a recent study, it creates a stronger shield against the coronavirus, providing babies with a rich source of antibodies for at least three months after their mothers are vaccinated.
“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,” said study author Jeannie Kelly from Washington University in St. Louis.
According to Kelly, at the end of the study, antibody levels were still high, indicating that the protection likely extends for even longer.
The pilot study included a cohort of five breastfeeding mothers who received both doses of the Pfizer-BioNTech COVID-19 vaccine. The women provided weekly frozen breast milk samples from before they got vaccinated, to 80 days after the shot. The researchers analyzed the samples for the presence of immunoglobulins IgA and IgG, antibodies in breast milk that are known to coat the babies’ mouths and throats, protecting them from infections.
Kelly and team found that IgA and IgGs in breast milk spiked immediately after the first vaccine shot and continued to rise to immune-significant levels in around two weeks after the first vaccination in all the study participants.
“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,” commented senior author Misty Good.
“Our paper is the first that has shown COVID-19 antibodies persist in breast milk for months following the mother’s vaccination.”
Kelly says that a growing amount of evidence in the field is helping physicians provide new mothers with data-driven advice on how to protect themselves and their babies during the pandemic.
“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.”