A Python simulation of Herd Immunity from vaccination (in Python subdirectory) for the interpreter: https://www.python.org/downloads/
C++ port is in CPP subdirectory. to build from source requires the following
cmake version 3.1+ (http://www.cmake.org/) -- a makefile generator
tclap (http://tclap.sourceforge.net/) -- a header-only library, meaning you don't have to compile it ahead of time to use it.
if you are on linux, both of these should be in your distribution repository, although cmake 3.1 is fairly new (as of April 2015 it is still in Fedora rawhide & fedora 22 testing repos), you may need to enable testing or raw repositories to get it.
on mac you might need to use xcode + macports, homebrew, or something similar to pull these down and build them.
on windows I would recommend using mingw or cygwin
It may also work with the microsoft visual c++ compilers via cmake, but you'll still need tclap.
chances are if thats your setup, you'll know how to set up your environment.