Pregnant or nursing mothers are vaccinated to protect their young infants from disease because infants generally have weak immune systems, making it difficult for them to fight infections. For nursing mothers, breast milk serves as the medium to pass on protective antibodies to infants.
“Think of breast milk as a toolbox full of all the different tools that help prepare the infant for life. Vaccination adds another tool to the toolbox, one that has the potential to be especially good at preventing COVID-19 illness, “Josef Neu, MD, the study co-author and a professor at the University of Florida, said in a press release.
Although several studies show that the breast milk of mothers who have recovered from COVID-19 infections contains protective COVID-19 antibodies, there’s limited evidence showing that vaccinated mothers’ breast milk also contains protective antibodies.
Notably, a team of researchers at the University of Florida has now added to existing evidence by showing that COVID-19 antibodies are present in vaccinated mothers breast milk and may protect nursing infants from COVID-19 infections.
The study, “Detection of SARS-CoV-2-Specific IgA in the Human Milk of COVID-19 Vaccinated Lactating Health Care Workers,” was published in Breastfeeding Medicine.
For the study, researchers followed 22 lactating health care workers (95% Caucasian) who had never contracted COVID-19 between December 2020 and March 2021. The women were at least 18 years old, and all received two doses of either the Pfizer/BioNTech or Moderna/NIH vaccines.
To assess the number of antibodies they produced, the women provided blood and milk samples at three time points: before the vaccination, 16–30 days after the first vaccine dose, and 7–10 days after the second vaccine.
After analysing their blood and breast milk samples, the researchers found that antibody levels after the first vaccination were significantly higher than pre-vaccination in both blood and breast milk, further significantly increasing after the second vaccination.
“We saw a robust antibody response in blood and breast milk after the second dose – about a 100-fold increase compared with levels before vaccination,” Lauren Stafford, a doctoral student at the University of Florida, said.
“These levels are also higher than those observed after natural infection with the virus,” Vivian Valcarce, MD, a resident in the University of Florida College of Medicine’s department of paediatrics, division of neonatology, said.
Vaccinating pregnant or nursing mothers is standard practice to prevent several infections. For instance, mothers who receive vaccinations against whooping cough in the second/third trimester of pregnancy or immediately postpartum produce antibodies that protect their babies from the virus. However, future research is necessary to determine if the COVID-19 antibodies in breast milk protect babies who consume it.
“We would like to know if infants who consume breast milk containing these antibodies develop their own protection against COVID-19,” Joseph Larkin III, PhD, senior author of the study and an associate professor in the University of Florida/IFAS department of microbiology and cell science, said. ‘We would also like to know more about the antibodies themselves, such as how long they are present in breast milk and how effective they are at neutralising the virus,” he added.
The team are also interested in learning more about breast milk’s benefits and investigating the potential uses of antibody-containing breast milk of vaccinated mothers.
“There is still so much we are learning about breast milk and all its benefits, and that’s what makes this research so fascinating – not just for us scientists but for non-scientists too,” Stafford said. “We are also excited to see many other simultaneous studies conducted around the world that also show antibodies in the breast milk of vaccinated mothers,” New added.
Overall, “our findings show that vaccination results in a significant increase in antibodies against SARS-CoV-2 – the virus that causes COVID-19 – in breast milk, suggesting that vaccinated mothers can pass on this immunity to their babies, something we are working to confirm in our ongoing research,” Larkin said.