“Cure” is episode ten of season six of Stargate SG-1.
SG-1 arrive on a world whose people are pleased to meet them and want to share technology with them. In return, they offer a new drug that boosts the immune system, and prevents illness. The drug does have some side effects, naturally. These are said to be not that serious. Famous last words.
Something weird is going on as well, and it seems to be connected to the source of the miracle drug. Which is related to Goa’uld symbiotes. The Tok’ra get brought in to try and help, as there is something also weird related to the Goa’uld symbiotes.
There is a connection to the Tok’ra too, which causes problems.