HIV doesn’t mutate in the same way a disease like Covid does, at least not at the same speed— also, 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).

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).