Breast Milk Antibodies Fought Flu and RSV in Lab Tests

Breast Milk Antibodies may be the most underrated immune system on earth. New research from a Canadian university shows that antibodies purified from donated breast milk neutralized flu viruses, RSV and adenovirus in the lab — and when delivered through the nose, they fully protected mice, including mice with weakened immune systems. The work points to a future where a nasal spray of ready-made antibodies could shield the people that vaccines cannot reach.

The findings, published in October 2026 in the journal Science Advances, come from a team led by biochemistry professor Matthew Miller, working with the U.S. biotechnology company Lactiga. Researchers pooled milk from 120 donors through milk banks in Indianapolis and Pittsburgh, purified a type of antibody called secretory immunoglobulin A, and tested the mixture against respiratory syncytial virus, adenovirus and influenza strains including a highly pathogenic bird flu subtype. According to the university's announcement, the antibody mixture neutralized the virus in every case, demonstrating a broad spectrum of antiviral activity.

The idea borrows from nature's original delivery system. Breast milk is essentially a record of everything a mother has encountered through infection or vaccination, and nursing passes that record to the baby as stopgap protection until the infant's own immune system matures. The twist in this study is pooling: antibodies in one person's milk can look entirely different from another's, depending on each donor's history, so combining samples from many donors produced a far more diverse cocktail than any single donation could offer — one broad enough to take on several unrelated viruses at once.

From lab dish to nasal spray

The animal experiments are what turned heads. Two intranasal doses — one given two hours before flu exposure and another a day afterward — reduced illness and lung damage in both healthy mice and mice unable to make their own antibodies. In the immunodeficient animals, delivering the antibodies through the nose rather than into the bloodstream provided complete protection. That delivery detail matters: current antibody therapies are usually infused directly into veins, while a nasal dose lands exactly where respiratory viruses enter the body.

The approach is called passive immunization — handing the body ready-made antibodies instead of waiting for it to manufacture its own after a shot or an infection. Vaccines remain the gold standard for most people, but they depend on a working immune system and weeks of lead time. A nasal antibody spray would act immediately. "This is particularly useful for people with immunodeficiencies, and could be an excellent rapid-response measure during outbreaks and pandemics," said Miller, the study's principal investigator. His team suggests the same platform could one day be aimed at seasonal flu prevention or stockpiled for the next pandemic.

The caveats scientists want you to hear

Enthusiasm comes with asterisks, and the researchers are upfront about them. Efficacy in humans has not been established — mice are not people, and lab-dish neutralization does not guarantee real-world protection. News-Medical reports that the preparation showed little neutralizing activity against one tested bird flu strain in the dish, even though it bound the virus's proteins, and animal protection against that strain was not tested. Scaling up would also mean reliably sourcing large volumes of donor milk through established milk banks, and regulators would need convincing that a pooled human product is consistently safe.

Who could benefit first

If the science holds in people, the first in line would likely be the groups flu season hits hardest: premature infants too young for full vaccination, transplant recipients, cancer patients on immune-suppressing therapy, and older adults whose vaccine responses fade with age. For them, Breast Milk Antibodies would not replace vaccines but fill the gap that vaccines leave — immediate, needle-free protection delivered exactly where the virus lands. The bigger idea may outlast any single product: milk banks already exist in dozens of countries, and treating their donations as a renewable library of immune memory reframes something deeply ordinary as medical infrastructure.

For more on new health research, read what a daily walk does for your immune system and why diabetes risk peaks in the first 90 days on antipsychotics, according to a new study.