> Doesn't "you" imply that "you" were actually named.
No, defamation doesn't require you to specifically be named. It's enough for them to be identified with enough specificity that they are harmed.
> If a politician says the unvaccinated are terrible people for spreading the disease
There are two claims in the phrase "the unvaccinated are terrible people for spreading disease".
The first claim, that they are terrible people, is not a statement of fact, but is rather an opinion. There is no factual, objective, way to determine whether someone is "a terrible person". So that part would not create the potential for liability.
The second claim "the unvaccinated are spreading disease" _could_ potentially be defamatory, but truth would be an absolute defense. The truth also doesn't have to be _perfect_ so long as it's "correct in the main". First, note that the claim "the unvaccinated are spreading disease" is still true even if the vaccinated are also spreading disease. So, your defamation claim would need to first convince the jury that the implication of the statement is "the unvaccinated are spreading disease *more than the vaccinated*". I think that implication is there, but it's a little more tenuous of a claim. Second, I don't think there would be any liability, since the vaccine has some efficacy. To defend against the defamation claim, it would be sufficient to show that the vaccine has any significant efficacy. You wouldn't need to demonstrate that the vaccine has perfect efficacy. The vaccine does have efficacy against COVID-19, so I think a defamation claim would fail here.
Finally, you'll need to go to the harms. It's going to be very difficult to demonstrate significant harm to any individual unvaccinated person, when the group includes 100M people. The harm is going to be _very_ diffused, and I think it would be difficult to demonstrate any economic harm.
So, on balance, I think a politician would still be very safe making the statement you suggested, even in light of the fact that a person doesn't need to be specifically named to press a defamation claim.