From the birth canal and beyond, infants are confronted by a host of different challenges to their immune system. Their intestines encounter foreign proteins in milk and formula. Their lungs encounter bacteria inhaled on the surface of dust in the air. And literally thousands of different bacteria immediately start to live on the skin, as well as on the lining of the nose, throat, and intestines. Here is how infants deal with this immediate confrontation to their immune system.
Babies have a tremendous capacity to respond to their environment from the minute they are born.
The newborn has billions of immunologic cells that are capable of responding to millions of different microorganisms. By quickly making an immune response to bacteria that live on the surface of their intestines, babies keep those bacteria from invading their bloodstream and causing serious disease. Therefore, the combination of the three vaccines contained in MMR, or even the 10 vaccines given in the first 2 years of life, is literally a raindrop in the ocean of what infants successfully encounter in their environment every day. The third invalid theory is that the MMR vaccine is given by an unnatural route. The rationale behind this theory is that children do not normally encounter viruses or bacteria under their skin or in their muscles.