Note that while it is not a vaccince, there is an injectable birth control, and immunocontraceptives which would actually be vaccines are in development. Further there have been well documented cases where people were sterilized against their will under the guise of other medical procedures, including receiving such shots. It really doesn't take too much whisper down the lane for that to be misunderstood, and once you get it in your head that a vaccination program could be used for population control I imagine it would be pretty hard to find evidence to convince yourself otherwise.