The basic premise is that the community needs to be inoculated enough so that any breakout doesn’t have enough viable hosts around to jump to and dies out before it can gain momentum among a wider population. This benefits others in the community who are still vulnerable for whatever reason and is a legitimate argument for why people should care if other people get vaccinated. If the threat is dire enough it could even be argued that others should be forced against their will. The costs of implementing herd immunity can be quite high, as well as the benefits—but for us to begin even thinking about whether it’s worth paying, we must be sure we can realistically achieve it.
If the level of inoculation among the population is too low the virus will spread. That’s what’s important—that’s why it’s all or nothing. The fact that it’s slower, or that it won’t overwhelm hospitals as quickly, is so trivial in comparison as to be inconsequential. The only thing that matters is that it’s still there. Fast or slow, it will still infect the entire world, and the vulnerable won’t be safe.
Given all of the above, it goes without saying that a vaccine that only stops a virus from making you sick but doesn’t stop it from spreading is next to useless when it comes to herd immunity—that much should be obvious. I would think it should be obvious too that the covid vaccine is one of such a type, but if you’re interested in arguing that here or elsewhere—or anything else for that matter—please know that ridiculing and dismissing others because you think they’re so obviously wrong and incapable of being saved, is in fact the only thing preventing anyone from trying to fix it.
So… actually that’s not the case. They’re only free at the point of sale. The government buys them. They’ve made money on every single one.