Johnson & Johnson subsidiary Janssen has launched a clinical trial of its experimental Ebola vaccine in the UK, with much larger clinical studies expected to start this spring in the U.S. and Africa.

The Phase I trial, which aims to enroll 72 patients by the end of the month, will consist of an initial dose to prime the immune system followed by a booster dose. Patients will be divided into four treatment arms, randomized to receive either the active vaccine or a placebo.

Janssen and partner Bavarian Nordic have produced roughly 400,000 doses of the vaccine that it hopes to use in larger trials in the U.S. and Africa by April, the company said. The drugmaker added that it expects to manufacture roughly 2 million doses throughout the year.

Results of the UK trial are expected in May, J&J spokeswoman Amy Meyer said.

Janssen's product joins other Ebola vaccines currently in human testing. The most developed is a vaccine by GlaxoSmithKline and the National Institutes of Health that is set to enter Phase II trials next month. — Lena Freund