>>13779496The first part about infection is correct, the second part is almost correct.
The vaccine doesn't actually weaken the virus particles, but it does two things:
First, it lowers the viral load, so the amount of virus particles that are present in your body. Because of that, the chances that you'll infect someone else are a little lower. Second, if you do get infected, your body recognizes and engages the virus more quickly, so the virulent period is reduced. In other words, if you've been vaccinated, the virus is in your body less long, so you're less likely to pass it on to others.
But it's important to keep in mind that these effects are not quite so large, and the primary means by which vaccination lowers the spread is through lowering the chances that you'll be infected in the first place.
