This study is testing two new vaccines for HIV, the virus that causes AIDS, in adults who already have HIV. The vaccines use a type of genetic material called mRNA (messenger Ribonucleic Acid) to help the body make antibodies, which are proteins that help fight infections. Participants will stop taking their regular HIV medicines for a short time, under careful watch, to see if the vaccines can still help protect them. About 42 people will join the study, which is a Phase 1 trial - the first step in testing new treatments to make sure they are safe and well-tolerated. Participants need to be in good health and have their HIV well-controlled with current treatments.

• Participants will need to stop their regular HIV medications temporarily during the study.
• Participants must agree to use condoms and not become pregnant during the study.
• The study will include multiple visits to the study center for monitoring and tests.