The Anti-aging vaccine is a powerful drug that was available to Earth citizens in an alternate future timeline, as well as a cure for a pandemic on the Aschen world of Volia several years before. In both cases, the vaccine intentionally causes an enormous amount of the population to become sterile in order to rapidly decrease the birthrate on a world within the Aschen Confederation. Almost a decade after the introduction of the drug about 91% of the population is unable to procreate. (SG1: " 2010")
The Aschen seem to patiently wait nearly twenty years for the vaccine to sweep into the genome of the entire race. Eventually there are so few individuals left that the advanced culture can effectively conquer the world, terraforming the planet so it is suitable for farming. In the process they often raise the remaining population themselves, brainwashing them into forgetting the past and providing maintenance to the farm land. (SG1: " 2001")
The Aschen more than likely used the vaccine for themselves, only without the sterility component, of course. This may contribute to their being "very patient", having more time to see long-term plans bear fruit.