Q&A with Lauren Stafford: Transfer of antibodies from vaccinated mothers to breastfeeding children

Disclaimer: The interview transcript has been modified into a blog-friendly format. The actual interview audio is available at the end of the blog.

We were lucky enough that one of the authors of the article “Detection of SARS-CoV-2 IgA and IgG in human milk and breastfeeding infant stool 6 months after maternal COVID-19 vaccination”, Lauren Stewart Stafford, decided to sit with us and talk about the research she has done. She is currently a third-year Ph.D. student at the University of Florida in the Microbiology and Cell Science department. She got her bachelor’s degree in Medical Molecular Biology and worked as a medical technologist in clinical laboratories for about five years before getting a master’s degree through the University of Florida. She then joined the Ph.D. program at Dr. Joseph Larkin’s Immunology lab. One day when she was just starting her lab work, Dr. Larkin offered her a COVID-19 breast milk project in collaboration with the Shands hospital, specifically their pediatrics department. She readily agreed. Let’s see what happened as the story proceeded…

Sounds like your mentor gave you an offer that’s hard to refuse! Where did the idea for the project originally come from? 

The lead investigator on our work, Dr. Vivian Valcarce, is a neonatology fellow at the University of Florida, and she also happens to be a breastfeeding mother of two little boys. So, with the epidemic on the rise, she wondered if she would be producing any COVID-19 antibodies in her breastmilk (if she got infected or vaccinated). She was able to have a really interesting cohort of participants because she worked at the hospital and healthcare workers were the first people to get vaccinated. 

Amazing story. Behind the research is always someone trying to protect someone close to them, a child, a family… Based on the research you performed, would you recommend the COVID-19 vaccine to pregnant people, and if yes, at what stage? 

Absolutely! There is so much work out there that suggests that vaccination during pregnancy provides infants with the systemic response that protects them when they first arrive into the world. And babies do need protection. Vaccinating during the later stage of pregnancy would be more beneficial, in my opinion. However, here we focused purely on tracking the breast milk transfer, so here, women were vaccinated after pregnancy. And I must say, I didn’t realize how much of a protective factor breast milk is until we started working on this study. The value of breast milk protection, sort of mucosal protection, plus getting to have a systemic response, is huge, especially as COVID is a respiratory disease. The funny thing about babies, is they spit up a lot when they’re drinking and it’s a protective quality because when they do it, some of that milk gets into their nostrils, and then they can spread those antibodies into intranasal mucosa.

I would like to follow up with the question about the vaccine booster during breastfeeding. Do you believe a booster would be a good solution, or, on the other hand, a bit much?

The clinicians we worked with worked in the NICU and had seen the nastiest side of this pandemic. They’ve seen unvaccinated moms come in and not get to go home because they have complicated pregnancies, complicated labor, and then sometimes pass away while they’re in the hospital from COVID complications. So just any amount of protection you’re able to mount with vaccination, you’re on the right track for sure. If you got vaccinated before pregnancy and then didn’t get any sort of booster or have any sort of exposure following that, your antibody levels would get low around 10 to 12 months post-vaccination. When you’re a mom, you wanna make every decision possible to protect your baby, and with all the misinformation out there, there is plenty of fear involved. I even had some friends who reached out to me and said, “Hey, my sister’s pregnant and she’s kind of worried” and I just gave them the information that I had that so far we see is safe and effective.

I think reaching out to you was great and that is something the general population should do: reach out to the closest person with some kind of knowledge in the area. We at Antibuddies applaud that. 

Going further, you had a pretty uniform group, meaning culturally, nationally, and racially there wasn’t such a huge variability. However, you still saw heterogeneity in this very similar group of people, – why do you think that is?

Exactly. Because it could be something as simple as you know, were any mothers taking antibiotics at the same time? Were any mothers taking probiotics at the same time? Did any mother or child have any sort of other infection or other issues? There are so many other things that could be affecting what we’re looking at.

You measured IgG and IgA in plasma, milk, and stool, but didn’t measure plasma IgG and IgA in babies’ plasma. Is it just because of the discomfort? Do you think the antibody concentration in the plasma could be higher than in the stool samples?

That was one of the reasons. However, we also focused more on the oral-gut response, which is a mucosal response, and not the systemic response. Because it is mainly mucosal (breast milk to stool sample), there is no plasma response. Based on that, the expectancy would be to see higher IgA antibody concentrations in stool samples rather than the baby plasma. Fortunately, the stool is a renewable source when it comes to babies!

‘Although breastfeeding infant’s stool, obtained both prior and subsequent to maternal vaccination could neutralize pseudovirus activity in vitro; the ability to neutralize pseudovirus activity was enhanced after maternal vaccination.’ 

Since the children were around 10 months (e.g. IgA production would start approx. 3 weeks after birth), when you measure the neutralization in post-vaccinated stool samples, could it be that you get double the effect (baby antibodies + mother’s breast milk antibodies)? Is there a higher concentration of antibodies in post-vaccinated stool samples?

Firstly, there are a lot of factors that likely went into the neutralization study. Maybe, non-specific coronavirus antibodies from previous infections and interestingly lactoferrin is possibly playing a role in this neutralization. We did see an increase in neutralization after vaccination where we could say, one of those variables led to increased neutralization. So we attributed at least some of that to immune response. I would also add, because babies were slightly older (10 months), they did have a different diet than what you would see in a newborn. Diet can also be another factor impacting the difference in neutralization. If you think about it this way – babies are producing antibodies that have non-specific roles in neutralization, however, the majority of neutralization is contributed by the addition of specific breast milk antibodies from the mom.

How were you able to rule out current (maybe asymptomatic) infections in babies and mothers? Maybe a test for IgM?

We didn’t test for IgM specifically, but if we had had a mom that was above the positive cut-off pre-vaccination, we likely would have scrapped her because of our exclusion criteria and the first study was you can’t have had COVID-19. I think it’s more likely to assume that it was the vaccination and not that all moms suddenly got COVID simultaneously. But no, we didn’t do anything to rule that out. And we relied on self-reporting, so moms would let us know if they had it. 

Fantastic story, but now we must know – what is next for you? Are you staying with breast milk research, or are you moving to a different area of research? 

The world is your oyster. You want to do everything and anything. If someone would have told me five years ago that I’d be doing this right now, I wouldn’t have believed it. I think I am interested and excited by this work and want to continue pursuing it in the future. I would like to look into what are the other factors in breast milk that are making these protective qualities for tiny humans.

Listen to the full interview to learn more:


Stafford LS, Valcarce V, Henry M, Neu J, Parker L, Mueller M, Vicuna V, Gowen T, Cato E, Kosik I, Yewdell JW, Atkinson M, Cacho N, Li N, Larkin J 3rd. Detection of SARS-CoV-2 IgA and IgG in human milk and breastfeeding infant stool 6 months after maternal COVID-19 vaccination. J Perinatol. 2023 Jan 12. doi: 10.1038/s41372-022-01581-5.

Article author: Ines Poljak. Ines is a Ph.D. student at King’s College. She worked at the University of Copenhangen on multiple myeloma bone disease. She worked in several clinical laboratories before committing herself completely to research.

Want your article featured in Antibuddies blog? Contact editor-in-chief- Dr. Sutonuka Bhar at antibuddies1@gmail.com.

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