Cyanide wouldn't work. People would drop dead instantly, resulting in others not getting injected. And you can't inject everyone all at once. In order to do what you want, the injections must have some sort of delay that only kicks in after everyone has gotten injected. The injections would also need to cause sudden death, because we can't have people being sick for a long time. It would need to attack a part of the body, that once damaged, can't be repaired. Like the heart. So they would need the injections to attack the heart. That way the damage can't be repaired, the deaths would be sudden. And it could be blamed on other things as the deaths pile up. And that would keep healthy working aged people alive until they start to get too old. *But how would they trick or force people into getting an injection like that?*