The antibodies from BF are IgA and do not interfer with vaccines. Mom's IgA will enter the child's GI tract and possibly upper respiratory tract. It doesnt get into the general circulation. Maternal antibody passed in utero is IgG and enter baby's circulation. There was a measles vaccine given at 8 months but maternal antibody interfered with it at this age. In the US at least this vaccine was discontinued in the around late 1980's or early 90's. A little before my time. OK no need for the Kathy D and Linda Smith style "Ohmygawd youre just a baby" and "help me across the street some time" comments. Breastfeeding enhances the responce to vaccines not interferes with them. For those with vaccine questions Id recommend "What Every Parent Should Know About Vaccines" by Paul Offit MD and Louis Bell, MD. The US CDC has an Email address to "ask the experts about vaccines. I dont have it handy but will find it. -Rob "In the face of such diseases, the most dangerous experiment of all is to do nothing." - Joseph Stokes, Jr, MD (1896-1972) in NEJM,1967, in reference to deaths caused by measles and mumps virus