Safety and Efficacy Study of Vaccine Schedule With Ad26.Mos.HIV and MVA-Mosaic in Human Immunodeficiency Virus (HIV)-Infected Adults

The purpose of the study is to assess: 1 safety and tolerability of adenovirus serotype 26 (Ad26) prime and Modified Vaccinia Ankara (MVA) boost versus placebo in participants on suppressive antiretroviral therapy (ART) that was initiated during acute Human Immunodeficiency Virus (HIV) infection; 2) Measure the frequency and duration of sustained viremic control after receiving Ad26 prime/MVA boost or placebo, defined as greater than 24 weeks with plasma HIV ribonucleic acid (RNA) lesser than (\<)50 copies/ml after antiretroviral (ARV) analytical treatment interruption (ATI).


Eligibility Criteria:
Inclusion Criteria:

* Confirmed human immunodeficiency virus (HIV)-1 infected and started antiretroviral therapy (ART) during acute infection (Fiebig stages I, II, III or IV) as part of trial RV254
* Treatment with current stable antiretroviral therapy (ART) (no changes to treatment) for at least 4 weeks prior to screening
* All female participants of childbearing potential must have a negative serum pregnancy test (beta human chorionic gonadotropin) at the screening visit, and a negative urine pregnancy test prior to vaccination on Day 1 and prior to subsequent study vaccinations
* HIV ribonucleic acid (RNA) less than (\<)50 copies per milliliter (copies/ml) for at least 48 weeks at screening: a) One blip of HIV RNA greater than (\>)50 and \<200 copies/ml within 48 weeks is acceptable, provided that the most recent (before screening) HIV RNA \<50 copies/ml
* Laboratory criteria during screening: a) Hemoglobin: Women: greater than or equal to \>=11 gram/deciliter (g/dL); Men \>=12.5 g/dL, b) White cell count: 2,500 to 11,000 cells per cubic millimeter (cells/mm\^3), c) Platelets: 125,000 to 450,000 per mm\^3, d) Alanine aminotransferase (ALT)/aspartate aminotransferase (AST) less than or equal to \<=1.5x institutional upper limits of normal (ULN), e) Creatinine \<=1.5x institutional ULN, f) CD4 \> 400 cells/mm\^3, g) Troponin \<1x ULN
* A woman must be either: a) Not of childbearing potential: postmenopausal (\>45 years of age with amenorrhea for at least 2 years, or any age with amenorrhea for at least 6 months and a serum follicle stimulation hormone \[FSH\] level \>40 International Units Per Liter (IU/L); surgically sterile; or b) Of child-bearing potential and practicing an effective double method of birth control (example, prescription oral contraceptives, contraceptive injections, intrauterine device, contraceptive patch, or vaginal ring, in conjunction with either a female condom or one of the methods for male contraception before entry and through 3 months after the last vaccination

Exclusion Criteria:

* Receipt of any vaccine within 30 days prior to the first vaccination or plans to receive within 30 days post-vaccination. In the case of medically indicated vaccines, the vaccination should be given at least 2 weeks before or after the first vaccination. However, if a vaccine is indicated in a post exposure setting (example, rabies or tetanus), it must take priority over the study vaccine and same rules will apply to subsequent study vaccinations
* Any history of HIV-related illness under Centers for Disease Control and Prevention (CDC) category C
* History of myocarditis, pericarditis, cardiomyopathy, congestive heart failure with permanent sequelae, clinically significant arrhythmia (including any arrhythmia requiring medication, treatment, or clinical follow-up)
* Chronic active hepatitis B or active hepatitis C (for example, positive serology with confirmatory positive polymerase chain reaction) or active syphilis infection. Active syphilis documented by examination or serology unless positive serology is due to past treated infection
* Receipt of blood products or immunoglobulin in the past 3 months
* History of anaphylaxis or other serious adverse reactions to vaccines or vaccine products, or neomycin or streptomycin or egg products
* History of chronic urticaria (recurrent hives)
* Chronic or recurrent use of medications which modify host immune response, example (e.g.) cancer chemotherapeutic agents, parenteral corticosteroids (short course oral steroids given for non-chronic conditions not expected to recur is not an exclusion criteria, topical steroid use is not an exclusion criteria), etc. but not including ART