Here's how the "depopulation" script played out in the old Stargate SG-1 series:

"The Aschen, who lack advanced military capabilities, use a slow-acting bioweapon to seize control of other planets. At first, the effect of their vaccine isn’t obvious, but then the birth rate among the target population starts to drop. Within a decade, 91% of the population is sterile. The plan is genius, because the Aschen never have to fight; all they need to do is wait..."

Source: dystopianliving.substac…

Here's a review of previous vaccine programs led by the WHO etc designed to cause sterility: amidwesterndoctor.subst…