Once I’m vaccinated, can I pass on the antibodies to my baby by breastfeeding?

Families Vaccines

Q: I’ve had the vaccine and am nursing. Can I pass the antibodies along to my newborn?  Would post-vaccine frozen breastmilk also benefit other family members?

A: We are so glad you asked! Yes, we do have limited preliminary evidence that breastmilk can confer some protection against SARS CoV-2 to your newborn.

Sadly, we don’t have evidence that breastmilk can help protect anyone else (just yet).

Before we dive into our explainer, we want our readers to know that we support all forms of feeding a baby, but wanted to answer these reader questions about breastmilk specifically.

🧱 Breastfeeding is an important way to acquire antibodies and other molecules that are protective to the respiratory and gastrointestinal tract in early life. Early studies suggest that birthing individuals who are positive for COVID-19 can pass on antibodies to their babies during pregnancy. A fall 2020 study of 18 women who were COVID-19 positive and breastfeeding suggests that antibodies to SARS-CoV-2 are present in breastmilk, implying that continuation of breastfeeding may be beneficial for the baby. Specifically, most of the samples collected from breast milk in this population contained IgA and IgG antibodies. Evidence from the study also suggested that there were antibodies that could neutralize SARS-CoV-2. The study included data from 18 individuals at several time points from infection to 2-3 weeks post-infection. Antibodies can last in human milk at least 3-4 months following infection in the mother with COVID-19.

💪🏽 Note: IgA may be more prevalent in early infection and play an important role in defending mucosa (like the nose, mouth, and throat) from viral entry by blocking the virus from attaching and getting into cells. IgA antibodies exist in breastmilk because IgA is a secretory antibody, defined as an antibody that is intended to be extra strong (it has an extra chain in its structure) so that it can exist in secretions. IgG may have lower neutralizing capabilities than IgA and represent a more delayed or systemic response. Neutralizing antibodies stop the virus from entering the cell, which can prevent reinfection. Also of significance, antibodies present in breastmilk may exist in varying proportions compared to antibodies existing throughout the body.

🛡️A recent preprint (not yet peer reviewed but important enough to publish quickly) suggests that antibodies are also present in human breastmilk after maternal vaccination. In the study, 6 lactating individuals provided breast milk samples immediately after the first vaccine dose and up to 14 days after the second dose. Individuals received either the Pfizer or Moderna vaccine. For all participants, IgG and IgA (specific to the SARS-CoV-2 spike protein) increased and was detectable in breast milk 7 days after the first dose of the vaccine with a notable increase in detection after the second dose. Importantly, IgG was prevalent in breast milk (in contrast to IgA, which was more prevalent in individuals previously infected with SARS-CoV-2), perhaps because of the injected viral antigen into the muscle rather than infection via mucosa.

✔️It is important to note that although antibodies were present in breastmilk, the emergence of COVID-19 cases in babies born to individuals who had COVID-19 or received the vaccine was not tracked. Thus, it is implied that the presence of antibodies in breastmilk contributes to protection from SARS-CoV-2. This is a reasonable conclusion given prior studies in flu vaccine. This evidence combined is promising news, but more information is needed to understand what the immune response is and how long it will last.

🤔In addition, it is unknown if other individuals can benefit from breastmilk. To be clear, this must be tested in the lab to understand how protection can best be delivered. It is unlikely that the consumption of breastmilk by those other than neonates/infants will confer immunity. Consuming breastmilk from a vaccinated individual is not recommended.

Stay safe. Stay Sane.

With love,
Those Nerdy Girls

Easy to read summaries:

The Scientist


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