Forgive my basic understanding of biology, but I've been worried about the following:

If the current COVID vaccines are 'leaky', in that they only prevent symptoms instead of preventing infection, then doesn't mass vaccination lay the groundwork for a potential escape variant that is much more transmissible and/or severe in terms of symptoms?

If the answer is yes, then wouldn't it be better to only vaccinate only the vulnerable ones?

If the answer is no, then how is it different from, let's say, overusing antibiotics, which can lead to potential superbugs due to a similar evolutionary pressure?

Thanks in advance