Fewer Ebola cases put potential vaccine at risk | Science| In-depth reporting on science and technology | DW | 27.01.2015
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Fewer Ebola cases put potential vaccine at risk

The good news is, there are fewer Ebola infections. But in the world of vaccine research, that's bad news. Scientists about to start Phase II and III studies in West Africa will have to hurry.

A doctor talks to his staff in Freetown (Photo: Reuters)

Phase III studies in West-Africa are scheduled to start in early February

Researchers worldwide are confident that vaccines for Ebola may soon be ready for the market. Two vaccine candidates are currently available, one of which is about to enter a combined Phase II and Phase III study in February.

British pharmaceutical company Glaxo-Smith-Kline (GSK) has already shipped the first 300 of 10,000 vaccine doses to West Africa, where 30,000 are going to participate in the study. A full 20,000 will not receive the vaccine, as they will belong to control groups.

GSK's vaccine combines a cold virus which only affects chimpanzees with specific parts of the Ebola virus that are unable to trigger an infection. The other is based on a herpes virus that is infectious to cattle, pigs and horses. Both cause minor side effects: slight fever and temporary joint pains - expected reactions.

A Hand with rubber gloves Holding an Ebola-vaccine (Photo: Reuters)

Two different Ebola vaccines have cleared Phase I studies

Fewer patients, less data

Now, however, a paradoxical situation has emerged for the researchers.

Just as the vaccine is ready to be tested, that number of infected patients is on the decline. There are still new infections, but far fewer than before. And only if there is a large number of Ebola infections can researchers determine with certainty whether a vaccine is working or not.

"In that sense, we now have this completely ridiculous situation where, on the one hand, we're quite happy that the Ebola outbreak seems likely to have come under control over the next few months," saysProf. Stephan Becker, https://www.uni-marburg.de/fb20/virologie/forschung/beckerfold, a virologist at the University of Marburg.

"But now, we really have to work quickly to get the data we need to collect."

Next phases

Ebola-vaccine being administered in Mali (Photo: dpa)

Only Phase III studies will provide certainty about effectiveness of the vaccines

Previously, Becker's team tested blood samples from 200 participants in a Phase I trial, searching for antibodies.

His conclusion: "For now, it looks like these vaccines actually trigger an immune response." In other words, they're successful.

The upcoming Phase II and Phase III clinical trials are therefore a crucial step.

In the first phase, most participants will be doctors, nurses other medical personnel and undertakers.

"Then we have to check whether those people get infected or not," the virologist says.

The larger-scale Phase III study of 30,000 people will be conducted together with US health agency NIH.

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