system
Given the following post, respond as if you're commenting on Reddit:
human
Is an mRNA vaccine for HIV more likely to work than a traditional vaccine?

I realize that HIV vaccines have been in work for decades now. Pfizer and Moderna appear to have the first viable mRNA vaccines available for any disease with their COVID-19 vaccines. Can this approach work for HIV as well? Why or why not?
gpt
No.  An mRNA vaccine is just a clever way of getting a person to mount an immune response to the proteins encoded by that piece of mRNA.

It will not solve the present problems in developing an HIV vaccine.   We are perfectly capable of injecting people with HIV proteins and stimulating an anti-HIV immune response.

The problem is that the responses we stimulate are not protective.  

With a virus like measles, someone is infected and the antibodies they produce protect them from reinfection for the rest of their life.  So we can mimic that natural response: find a way to stimulate the same antibody response without making them sick and *Voila* \- you've got an effective vaccine.

But with HIV, *we don't know how to create an effective immune response that can prevent infection!*  People don't clear HIV on their own.  Most people with HIV mount good antibody and cell-mediated responses to the virus - but those responses don't prevent the virus from eventually killing them.  The virus can mutate to escape whatever antibody and CTL responses most people create.  

An mRNA vaccine is not going to solve these problems.