You don't get 72 vaccines.
You get 49 doses of 14 vaccines by 6 and 69 doses by 18 if you follow the recommended schedule.
http://www.nvic.org/CMSTemplat...
Part of the reason we do the vaccines this way is because we now know more about the immune system and how effective the shots are / how long they last.
Part of the reason we do the vaccines this way is because the less-toxic versions that have been developed since the 1960s are also less effective and must be administered more often.
Part of the reason we do the vaccines this way is because its the best way to give immunity for life. After six, you shouldn't need a booster for polio, measles, varicella, or several others.
Either way, nobody gets 72 vaccinations.
With your bare hands?!?