Jan 13 (Reuters) - Johnson & Johnson's COVID-19 vaccine candidate should hopefully show high effectiveness of 80% to 85%, the chief adviser for Operation Warp Speed Moncef Slaoui said on Wednesday.

"My expectation is high efficacy," Slaoui said at a J.P.Morgan healthcare conference, noting that he hoped anything at 80% or above would receive emergency use authorization in the U.S.

The vaccine, not yet authorized for emergency use in the United States, is in late-stage trials as a single dose vaccine, in contrast to rival two-shot vaccines from Pfizer Inc and Moderna Inc.

Operation Warp Speed is the U.S. government's program to develop and distribute COVID-19 vaccines. (Reporting by Manojna Maddipatla in Bengaluru; Editing by Shounak Dasgupta)