With the latest outbreak of measles in the United States, many breastfeeding moms are wondering whether or not their infants will obtain enough protection from their milk.  We know that breastfed babies have reduced risks of diarrhea, otitis media, SIDS, Crohns disease, ulcerative colitis, asthma, juvenile diabetes, severe upper respiratory infections, childhood cancers, , obesity and more … but will the simple act of breastfeeding be enough to protect the baby who can’t receive the MMR vaccine until 12-15 months of age?  The short answer is “no”, tho read on for further explanation.
Fact:  Babies of vaccinated moms do obtain immunity thru the placenta (transplacentally) that can last for several months after delivery but it does ware off sometime before a year of age.  In Ruth Lawrence’s book:  Breastfeeding:  A guide for the medical professional it says:  “postnatal exposure leading to measles after 14 days of life is generally mild, probably because of passively acquired antibodies from the mother.  Severe measles in children younger than 1 year of age may occur because of declining passively acquired antibodies.”
There was a study performed back in 1995, which by today’s standards is “out of date”, but when you consider that measles was basically eradicated in the US in 2000, there was no need to do another study.    Afr J Med Med Sci  (1995)  Dec;24(4):385-8
In the study, they sampled 216 moms breastmilk and took finger prick blood samples from their babies.  41 milk samples had antibodies to measles present, but none of the breastfed babies showed antibodies in their blood – thus the conclusion was made that “very little level of measles antibodies are passed through breast milk”.
In summation, while there are measles antibodies in the breastmilk of either vaccinated or naturally acquired moms, these don’t appear to get out of the babies gut and into the bloodstream, thus is not enough to prevent the baby from getting the measles.