Fortunately, babies are born with antibodies supplied by the mother. This is why we have mostly IgG antibodies, even though IgM is more effective. IgM is too large to cross the placenta.
Each of those little blue and orange structures are grabbers that attack germs. Notice IgM is very well-armed which is why it's more effective. Unfortunately it's too big to cross the placenta. So we mostly do with IgG.
Mother's antibodies amount to "passive immunity", which goes away in the first few months of life. This is why immunizations are put off until that passive immunity goes away, and the baby can form it's own immunity.
This is true. We, in America, are often way too obsessive about keeping kids clean. It's a good idea to let them get dirty and play in the dirt occasionally. The only reason we have polio vaccines, is because kids aren't normally exposed to the virus until they are too old to handle it well. You don't see paralytic polio in many third-world nations that have less obsessive mothers; by the time the kid is old enough to get paralytic polio, he's already encountered the virus, had a low-grade infection and has become immune.
At best, it won't be as healthy.