On Vaccines and Breast Milk
If you've found yourself wondering what's in your baby's milk, down to the smallest molecule, you are in very good company. Asking questions about vaccines, antibodies, and what transfers through breast milk isn't anxious or overprotective. It's the work of a thoughtful parent.
What we care about at MaiaMilk is giving mothers options, real information, and the dignity to choose what feels right for their family. So if this question has been on your mind, here is what the science actually says.
The short answer
Vaccines themselves do not transfer into breast milk.1 What does transfer is the body's response to a vaccine: antibodies. And those antibodies offer gentle immune support to a breastfeeding infant.2
This isn't new science. It's the same passive immunity that infants have received from their mothers for as long as humans have been breastfeeding, now layered with the added benefit of modern immunization.
What the research actually shows
The CDC's General Best Practice Guidelines for Immunization confirm that inactivated, recombinant, subunit, and conjugate vaccines pose no risk to a breastfeeding mother or her infant.1 The vast majority of live-virus vaccines have also been shown not to be excreted in human milk in any meaningful amount.1
What does show up in the milk: antibodies. Studies of maternal influenza, pertussis, and COVID-19 vaccination have all documented the transfer of pathogen-specific antibodies through breast milk,2,3 including secretory IgA, the antibody class that coats and protects mucosal surfaces like a baby's gut and respiratory tract.2
In other words, when a lactating parent gets vaccinated, the milk doesn't carry the vaccine. It carries the body's response to it.4
Vaccines don't pass through breast milk. Antibodies do.
What this means for donor milk
This is also why MaiaMilk does not screen or exclude donors based on vaccination status. The medical choices of the people providing the milk are personal, and they are not ours to vet. The integrity of the milk itself is what we measure, test, and stand behind.
Every batch is held to the same rigorous standards regardless of donor vaccination status: comprehensive donor screening, batch testing for pathogens and contaminants, and third-party lab verification.
The antibodies a body produces in response to a vaccine function the same way as those developed through natural exposure. Both are part of normal immune function, and both can offer some quiet, passive support to a baby.
A note on timing
Out of an abundance of care, our donors pause for 48 hours after any vaccination before continuing donation. This isn't because we believe vaccine components are present in milk. It's a conservative buffer, rooted in respect for the donor's body and the parent feeding it.
The bottom line
Vaccines don't pass through breast milk. Antibodies do. Whether you vaccinate, partially vaccinate, or choose not to, that's your decision to make for your family. Our job is simply to make sure that the milk in your hands is exactly what we say it is: pure, tested, and trusted.
