In recent months, several prototype Ebola vaccines have been rushed through development, a process which usually takes up to 10 years. But even the most promising will not have completed testing for safety and efficacy before the end of next year.
Nearly 5,000 people have died from Ebola in West Africa, and there are signs that the spread of the virus is still increasing in Sierra Leone, although it appears to be slowing down in the worst-hit country, Liberia.
Potential vaccines must first be tested for safety. The most promising candidate, ChAd3 from GlaxoSmithKline (GSK), is being tested at the Jenner Institute in Oxford, the National Institutes of Health in Maryland, USA, and in Mali.
It has been funded by a ?2.8m grant from the Wellcome Trust, the Medical Research Council and the UK government. GSK has begun manufacturing additional doses ahead of the outcome of trials, with 10,000 doses potentially available by the beginning of next year. If proved safe, the efficacy of the vaccine will be tested on healthcare workers combatting Ebola in West Africa.
Trials of another promising vaccine, VSV, are due to take place in Europe, Gabon and Kenya. Developed by the Public Health Agency of Canada, a ?3.1m grant from the Wellcome Trust will fund safety tests, with 800 vials of the vaccine donated by the Canadian government.
The virus was first discovered in 1976 and there have been more than 20 Ebola outbreaks since. However, all were on a much smaller scale to the current epidemic, meaning that, until now, there had been little momentum behind efforts to develop a treatment or vaccine.
The failure of governments and the pharmaceutical industry to develop one has led to calls for greater investment in vaccines for other rare but potentially dangerous 'outbreak' diseases such as Marburg, Sars and chikungunya.
Describing Ebola as "the most severe acute public health emergency in modern times", Dr Chan said there was "an urgent need to strengthen long-neglected health systems" in poorer states.
The WHO has itself faced criticism for its allegedly sluggish response to the crisis, and the organisation's regional office in Africa has been described as "not competent" by the co-discoverer of Ebola Professor Peter Piot.
- The Independent