Johnson & Johnson has started clinical trials of its experimental Ebola vaccine, which uses a booster from Denmark's Bavarian Nordic, making it the third such shot to enter human testing.

The initiation of the Phase I study in Britain, which had been expected about now, marks further progress in the race to develop a vaccine against a disease that has killed more than 8,000 people in west Africa since last year.

Two other experimental vaccines, one from GlaxoSmithKline and a rival from NewLink and Merck, are already in clinical development. However, the J&J vaccine offers a different approach, since it involves two separate injections.

US-based J&J said it had produced enough vaccine to treat more than 400,000 people, which could be used in large- scale clinical trials by April, and a total of two million courses would be available in 2015. Previously, J&J expected more than one million courses this year. It also now predicts it can make enough vaccine for five million treatments, if required, over a 12- to 18-month period.

Just how much Ebola vaccine will be needed depends on how quickly the epidemic in Liberia, Sierra Leone and Guinea is brought under control. Experts project demand at anywhere between 100,000 and 12 million doses. "As long as there are still Ebola patients, there is the risk that it will continue to go around the region," Paul Stoffels, J&J's chief scientific officer, told reporters.

The first volunteers have received initial injections in Oxford, where 72 healthy subjects will get different regimens involving various combinations of the vaccine components or a placebo.

Further studies are planned in the US later this month and soon after volunteers will receive the vaccine in Kenya, Uganda and Tanzania.

Phase I trials are designed primarily to test safety but may also indicate whether vaccines produce a good immune response.– (Reuters)