Who knows what's in those syringes!
There are a lot of claims about the mandatory vaccines including the seasonal flu vaccine, but perhaps the wildest claim is that the government is using the vaccine as a secret mind control device.
These fears have risen in response to the increased availability of flu vaccines, because until the last few decades, only children were routinely immunized. It's one thing to be able to control and/or track the youth of your nation, but obviously if you are going to run a respectable dystopic totalitarian nightmare shadow government, you need to implant this ability in adult citizens as well. Thus, the seasonal push to vaccinate adult Americans against a dangerous and highly communicable virus is framed as a heavy-handed measure to institute controls on the adult population.
The flu vaccine is also demonized because it is seen as one of the ways in which the government "touches" every citizen once a year. The problem with that theory is that the flu vaccine is neither created nor distributed by the government. Off the top of my head, IRS forms and annual car license tabs are much more direct annual routes to infection.
The purported method of the mind control varies by conspiracy. According to one theory, vaccines contain "miniscule tracking devices" which "act as beacons for various satellites." The flu vaccine doesn't just protect you from seasonal influenza threats; it also allows the government to track your every move. Why the government would want this ability is never made clear. I guess it will make it easier for the Terminators to track down the last remaining rebel forces.
In a variation of this belief, the implant is a secret ID chip that only the government can detect. (This seems like an unnecessarily technical solution to the problem of citizen identification, given that we all have fingerprints and DNA which can easily be tracked and collated.)
This four minute video purports to show the other form of threat being injected along with your flu vaccine: chemical means of controlling behavior. The video claims to be a clip of a presentation given at the Pentagon, but it has been widely debunked as a complete fabrication. Even if this were a real presentation, there's a wide gulf between "I'm giving a presentation to a mostly-empty room at the Pentagon" and "we have created and deployed this method of mind control."
(Besides, why would you want to dampen down people's religious spirits? I would think that doing so would also dampen their patriotism. I doubt any government would want to inoculate its own citizenry against patriotic thoughts.)