A Study of Heterologous Vaccine Regimen of Adenovirus Serotype 26 Mosaic4 Human Immunodeficiency Virus(Ad26.Mos4.HIV), Adjuvanted Clade C gp140 and Mosaic gp140 to Prevent HIV-1 Infection Among Cis-gender Men and Transgender Individuals Who Have Sex With Cis-gender Men and/or Transgender Individuals

The purpose of this study is to evaluate the vaccine efficacy (VE) of a heterologous vaccine regimen utilizing Ad26.Mos4.HIV and aluminum phosphate-adjuvanted Clade C gp140 and Mosaic gp140 for the prevention of HIV-1 infection in HIV-1 seronegative cis-gender men and transgender individuals having sex with cis-gender men and/or transgender individuals.

Human immunodeficiency virus type 1 (HIV-1) is a retrovirus that, if left untreated, can progress to acquired immunodeficiency syndrome (AIDS), a condition in which the immune system is severely compromised, leading to life-threatening conditions. Ad26.Mos4.HIV is a tetravalent vaccine composed of Ad26.Mos1.Gag-Pol, Ad26.Mos2.Gag-Pol, Ad26.Mos1.Env, and Ad26.Mos2S.Env. Clade C and Mosaic gp140 HIV bivalent vaccine contains: Clade C gp140, HIV-1 Env gp140 of Clade C, Mosaic gp140, HIV-1 Env gp140, and aluminum phosphate adjuvant. Evidences showed that a combination of vaccination with Ad26.Mos.HIV followed by Ad26.Mos.HIV together with Clade C gp140 protein in aluminum phosphate adjuvant led to highest level of protection observed so far with this vaccine concept. Study comprises of a screening period of 45 days, a 12-month vaccination period and a follow-up period of at least 18 months after fourth vaccination (until Month 30) in participants who remain HIV-1 negative or up to 6 months after diagnosis of HIV-1 infection in participants who become HIV-1 infected. Participants who completed their Month 30 visit will be followed for HIV infection, medically-attended adverse event (MAAEs) and serious adverse events until the end of study (Month 30). Primary analysis of vaccine efficacy will evaluate the number of HIV-1 infections in the vaccine group compared to number of HIV-1 infections in the placebo group between Month 7 and Month X (with 24\<=X\<=30) in per-protocol population.

Eligibility Criteria:
Inclusion Criteria:

* Individual is either cis-gender man having sex with cis-gender men and/or transgender individuals or transgender woman having sex with cis-gender men and/or transgender individuals or transgender man having sex with cis-gender men and/or transgender women or gender non-conforming individual having receptive or insertive anal and/or vaginal condom-less intercourse and who is considered by the site staff to be at increased risk for HIV-1 infection. The potential participants must in the last 6 months have had any condom-less receptive anal or vaginal sex (not included is condom-less anal sex within a mutually monogamous relationship \>=12 months if the partner is HIV negative or living with HIV and virally suppressed) or rectal or urethral gonorrhea or chlamydia or incident syphilis or any stimulant use or any other drug and/or substance which in the local context may be associated with increased HIV transmission (example, cocaine, amphetamine) or 5 or more sex partners
* Potential participant has a negative test result for HIV-1 and HIV-2 infection less than or equal to (\<=) 28 days prior to first vaccination
* Potential participant must be healthy based on medical history, physical examination, and vital sign measurement performed at screening
* Contraceptive use by participants assigned female at birth and who have not had sexual reassignment surgery should be consistent with local regulations regarding the acceptable methods of contraception for those participating in clinical studies
* All participants of childbearing potential must have a negative serum beta-human chorionic gonadotropin (beta-hCG) pregnancy test at screening and have a negative urine beta-hCG pregnancy test immediately prior to each study vaccine administration

Exclusion Criteria:

* Potential participants choosing to use PrEP. However, once participants are enrolled and received their first vaccination, and they change their mind regarding PrEP usage, they will be allowed to take PrEP according to the site PrEP plan and will continue to receive further vaccinations. The use of long acting PrEP is disallowed from 24 months prior to Day 1
* Potential participant is a recipient of a HIV-vaccine candidate at any time, or a recipient of other experimental vaccine(s) within the last 12 months prior to Day 1. For participants who received an experimental vaccine (except HIV vaccine) more than 12 months prior to Day 1, documentation of the identity of the experimental vaccine must be provided to the HPX3002/HVTN 706 safety review team, who will determine eligibility on a case by-case basis. Exceptions: participants can be included if the vaccine received (except HIV vaccine) was subsequently licensed or authorized for emergency use (example, Emergency Use Authorization (EUA), Emergency Use Listing (EUL), or similar program). Participants with proof of having received only placebo can also be included. Participants who are currently still in an interventional study of such a licensed/emergency use-authorized vaccine are to be excluded from the current study
* Potential participant has received an HIV-related mAb, whether licensed or investigational, within the last 12 months prior to Day 1. For participants who received an HIV-related mAb more than 12 months prior to Day 1, documentation of the identity of the mAb must be provided to the HPX3002/HVTN 706 safety review team, who will determine eligibility on a case-by-case basis
* Potential participant has known allergy or history of anaphylaxis or other serious adverse reactions to vaccines
* Pregnant, or breast-feeding, or planning to become pregnant while enrolled in this study or within 90 days after the last dose of study vaccination