In an attempt to address this issue, NASA is conducting a study in order to help find a way to thwart this semi-major problem.
(Space Daily) International Space Station crew members are collecting blood, saliva and urine samples to study their immune function in microgravity.
The National Aeronautics and Space Administration said while previous research conducted after landing showed dramatic changes in crew members’ immune systems, the on-going first-of-its-kind study is the only one to comprehensively monitor the human immune system before, during and after spaceflight.
This study is critical if humanity is ever going to live off world, especially since micro gravity gives harmful bacteria a dangerous advantage over our immune system.
Hopefully either NASA (or even the private sector) can find the solution to this problem, lest we have to build orbital space stations (which can be quite expensive) in order to dwell among the stars off world.