They prevent the plague and disease events from having an effect on your civilization, respectively.  (I believe they also cure them but the text on the Yor versions of the techs seems to imply that they are preventative only; however, they are simply a renamed copy of the older techs and as such should function as a cure as well.)  If you're playing with mega events off, you'll never see them, so you can safely exclude them from the tech tree should you choose to do so.

Oh, and 1000rp is expensive?  That's news to me.