A group of health workers in Mali are being given an experimental vaccine against Ebola. This will mean the Mali trial now has 40 participants. The research began in Mali following safety trials in the UK and the US. The vaccine itself has been designed by scientists at the National Institute of Allergy and Infectious Diseases in Maryland, in the US, and is being manufactured by the British drug company GlaxoSmithKline. The BBC's Africa Health correspondent Anne Soy was given access to the latest stage of the trials.