Ebola outbreaks have been occurring in Africa for the past 40 years. Ebola is an infectious and often fatal disease marked by fever and severe internal bleeding. It is spread through contact with infected body fluids. We know vaccines can protect people against some infectious diseases like measles and polio. New vaccines have been developed to protect against Ebola and studies with these new vaccines continue to better understand how they will protect people against Ebola. We are carrying out this study to find out if it is safe to give a booster dose to participants in the VAC52150EBL2002 study who received a 2-part Ebola vaccine, and if a booster dose helps the Ebola vaccine work better. The vaccine does not contain Ebola virus so it cannot make you sick with Ebola. This vaccine will not treat or cure people who are already sick with Ebola. The vaccine used in this study, called Ad26.ZEBOV, is dose 1 of the two-part Ebola vaccine (Ad26.ZEBOV, MVA-BN-Filo) you received in the VAC52150EBL2002 study. This vaccine has been given to over 100,000 people and has been shown to be safe and well tolerated. The 2-part vaccine that you received in the VAC52150EBL2002 study allowed people to develop antibodies in their blood that we hope will fight against Ebola. Antibodies can protect the body from illness by killing the germs (which cause infections) before they make a person sick. We do not know how long the antibodies in people’s bodies will last after the 2-part vaccine and we think that giving participants a booster dose of the Ad26.ZEBOV vaccine will increase antibodies against Ebola.

An open label, Phase 2 study to evaluate the safety and immunogenicity of an Ad26.ZEBOV booster dose in Human Immunodeficiency Virus positive (HIV+) adults previously vaccinated with the Ad26.ZEBOV, MVA-BN-Filo vaccine regimen.

RATIONALE In previous Phase 2 and 3 trials, vaccination of HIV positive adult participants with the 2-dose Ebola vaccine regimen (Ad26.ZEBOV, followed by MVA-BN-Filo) elicited humoral immune responses comparable to those in HIV negative adults 21-days after dose 2. However, the durability of vaccine-induced humoral responses was not known.

PRIMARY OBJECTIVES • To assess the safety and tolerability of a Ad26.ZEBOV booster dose in HIV positive adults previously vaccinated with the Ad26.ZEBOV, MVA-BN-Filo vaccine regimen. • To assess humoral responses induced by the booster dose against EBOV glycoprotein (GP), as measured by Filovirus Animal Non-Clinical Group (FANG) Enzyme-Linked Immunosorbent Assay (ELISA) at 7 and 21 days.

HYPOTHESIS As this study is designed to provide descriptive information regarding safety and immunogenicity without formal treatment comparisons, no formal statistical hypothesis testing is planned.