Shouldn't titers be checked?

Question: Shouldn't doctors check titers to determine if the child has been immunized before giving the booster shots?  For example, 30% of people can be successfully immunized with one Hib shot, 60% with two shots, and 100% with 3 shots (I'm making up the numbers but this captures the concept).  Therefore, instead of just giving 3 shots, doctors should check if the child was successfully immunized before unnecessarily given the additional ones, right?  It's more work but it's logical.  Does any doctor do this?
Background: A potential issue with vaccines is not only the mercury (which have been virtually eliminated except for the adult flu shot) but the number of shots especially given that vaccines stimulate the Th2 part more than the Th1 part of the immune system (because the immune system is exposed to the vaccine in a way different than the way things are normally exposed to the immune system).