This is a Phase 1a, first in human study in which healthy adult participants who are considered to be at low-risk for HIV infection and are seropositive for cytomegalovirus (CMV) will receive two doses of VIR-1111 or placebo. These participants will be assessed for safety, reactogenicity, tolerability and immunogenicity. There is an optional long-term follow-up study that would lengthen study participation for up to 3 years post-first dose.

Inclusion Criteria:

• Healthy males or healthy females of non-child-bearing potential between the ages of 18 to 50 at the time of screening
• Positive CMV serostatus
• Assessed by clinic staff as being low risk for HIV infection and committed to maintaining behavior consistent with low risk of HIV exposure through the last protocol visit
• Willing to use condoms during intercourse through Week 36 or the end of the study
• Willing to undergo HIV testing, risk reduction counseling, and receive HIV test results
• Willing to comply with the protocol requirements regarding donation of blood, sperm or other tissues
• In the opinion of the Investigator, generally in good health as determined from medical history and no clinically significant findings from physical examinations, vital signs, and laboratory values

Exclusion Criteria:

• Live in a home with children under the age of 6
• Routine provision of child care to children under the age of 6
• Have close contact with immunocompromised individuals
• Have close contact with pregnant women or a partner planning to become pregnant during the course of the study
• Health care provider who routinely comes into contact with immunosuppressed patients or pregnant women
• Participant is immunocompromised
• Participant has an autoimmune disorder
• Positive HIV test at the time of study screening
• Receipt of another investigational HIV or CMV vaccine candidate