Is there a likelihood the Extraterrestrial Alliance will rig a vaccine trial to falsely show effectiveness, so it will be embraced by the masses, but useless, except to deliver locater chips?

This, too, is likely to happen. When you think about the fact that the class of viral agents in question is more problematic than other scourges to induce immunity in people and a robust antibody response, producing a vaccine that works through those mechanisms will be correspondingly a greater challenge with a likelihood of being partially effective in a number of individuals, and only mildly so in some compared to the ideal of a very robust and hearty immunity that truly protects a person regardless of level of exposure. Under those circumstances, all that is required is tipping the balance enough to make the vaccine approach appear to be working and it will be embraced and promoted to give a false sense of security.