I think a lot of that's fair.
To the point of efficacy, of course the vaccine doesn't guarantee that someone won't catch the disease or transmit it, but it does massively reduce the chances of both. Even the 5-10% of people for whom it doesn't work are significantly protected by the 90-95% of people for whom it does; if you get the vaccine and unbeknown to you are still susceptible, the fact that most other people you come into contact with are immune means that your chances of getting it are massively reduced. This is the point of the flu vaccine, just because you don't care if you catch flu doesn't mean you shouldn't have it. You get the vaccine so you won't pass it to someone who can't take the vaccine because of their underlying conditions that make it a much more serious thing for them, and as we have seen this is a more serious and more infectious illness than flu.
I understand the point about the slippery slope, but I don't know that I buy it. If we're going to have such a fight over such a stupidly obvious thing as taking a well studied and researched vaccine for a global pandemic, I find it hard to believe that it's going to be an easy stepping stone to anything else.
Yeah I get the point about the vaccine, I didn't say don't take it or it doesn't help. The point is that it, like other things, only reduces the chance, and it doesn't seem mandating such a thing that only shifts the risk calculation is fair/embodying the principle of bodily autonomy in the first place.
To the second, certain countries likely will mandate the vaccine. Probably won't in most Western ones. But the slippery slope has already happened before; it will probably be different if it ever occurs again, but there's a chance it might. I'd rather pushback against it too early in the game than too late.
