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Epidemic Ebola vaccine passes safety test in Geneva trial

A health worker injecting a man with an Ebola vaccine in Conakry, Guinea, in March


The experimental Ebola vaccine partially tested at Geneva University Hospital (HUG) is safe and effective, results show. Attention now turns to follow-up trials in West Africa in the race to find a cure. 

According to the results of the phase one clinical trial carried out at the HUG and at partner institutions in Europe and Africa, one of the most promising vaccine candidates, VSV-ZEBOV, triggers the production of antibodies capable of neutralising the Ebola virus. 

These results, published on Wednesday in the New England Journal of Medicine, were based on 158 volunteers who participated in the trials that begun in November 2014.  

Most of the side effects from the vaccine were only “mild to moderate”, such as fever and muscle pain for one or two days. 

The vaccine was developed by Canada’s public health agency and is licensed to two US companies, NewLink and Merck. The product had previously been tested on monkeys. Several other experimental vaccine candidates are currently in the pipeline at different stages of development. 

Vaccines normally take years to develop, but the process has been fast-tracked due to the urgency. The current Ebola outbreak in West Africa has killed more than 10,300 people. 

“It was a race against time,” explained Claire-Anne Siegrist, principal investigator and head of the vaccinology centre at the HUG. 

“On September 10 we officially accepted the mandate from the World Health Organization (WHO). One month later the protocol was ready and submitted to Swissmedic [the Swiss Agency for Therapeutic Products] and one month later we had the authorisation to start the vaccination trial. I've never seen that before. It's not possible to go any faster.” 

African trials 

Attention now turns to West Africa: Guinea, Sierra Leone and Liberia. Phase three clinical trials recently launched there will determine whether the immune response triggered by vaccines like VSV-ZEBOV is able to protect the population against the Ebola virus, and whether large-scale campaigns are feasible. 

Liberia has largely succeeded in getting its Ebola outbreak under control and was on its way to completing the 42 days without a new case – necessary to declare the country free of the disease – when it recorded one infection last month. 

Sierra Leone has seen a fairly steady decline in cases in recent weeks. But the disease remains stubbornly entrenched in Guinea more than a year after the outbreak started and authorities are now stepping up efforts to eliminate the disease. 

“The question is not resolved,” said Laurent Kaiser, head of the infectious diseases department at HUG. “Most new cases have not been identified as coming from an established chain of transmission, which poses lots of problems. The epidemic is clearly not under control and another reason to advance with the vaccine.” 

‘Excellent response’ 

Last week the US National Institutes of Health reported that two experimental Ebola vaccines, one from GlaxoSmithKline and the other from Merck/NewLink, “appear to be safe” part way through a clinical trial being conducted in Liberia, which began on February 2. 

In neighbouring Guinea, testing also started using the experimental Ebola vaccine VSV-ZEBOV on affected communities last week. The WHO plans to vaccinate around 10,000 people. Health workers will immunise the high-risk contacts around Ebola patients, thereby creating a “ring of immunity” around them. The vaccine has already been administered to some volunteer healthcare workers. The WHO said the first teams had received an “excellent response” from residents. 

If the number of Ebola cases holds steady or increases, the WHO believes the Guinea study could be completed in six to eight weeks. But if the cases sharply decline, the outcome of the trial could encounter difficulties. Experiments need scores of patients with the virus in order to produce statistically significant results. 

Vaccine tests are due to start on 5,000-6,000 front-line health workers in Sierra Leone this month.

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