People are given a "dose" in the form of a message that causes a mildly painful reaction.
When the larger message with much greater potential pain is delivered later the resistant response to the later message is dramatically reduced.
You can observe this phenomena in your world where leaders think, plan and do the unthinkable. Had they attempted to release the virus pre-inoculation they would have caused revolt.
Instead the masses are made immune to the virus which comes in many smaller doses and then changes over a period of a few years. Each subsequent change garners less resistance.
Historically this method has an almost perfect track record when played out at nation levels.
You can utilize the same tool for good for others while leaders mess up the rest of the world around you...