I’m not a doctor, but as a gay man: it’s my understanding HIV doesn’t mutate in the same way a disease like Covid does, at least not in the sense that there’s as many opportunities to spread (i.e. not airborne), so while HIV may actually mutate more in theory, it gets less chances to spread, so less completely-different variants become widespread.

Also, as part of “stopping the spread” PrEP has existed for years. It’s still proven to be effective protection against contracting HIV even if directly exposed (though it’s a pill that must be taken every day rather than a vaccine). There’s also PEP that helps make you undetectable (untransmissable) if you do contract it (and as such, it’s no longer what many people still mistakenly regard as a death sentence).

I honestly don’t know why everyone who is sexually active isn’t on PrEP (the federal government even mandates it be free to those without insurance in most cases)— it should be as common practice as wearing a condom and birth control, yet its existence isn’t even known to many people (especially among straight people).