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Last Updated: Wednesday, 6 August, 2003, 23:20 GMT 00:20 UK
Breakthrough on Ebola vaccine
Ebola ward
Ebola has wreaked havoc in Africa
Scientists have developed a fast-acting Ebola vaccine that protects monkeys after a single shot.

If the vaccine proves similarly effective in humans, it may one day allow scientists to contain Ebola outbreaks quickly.

Ebola virus spreads easily from person to person, causes illness quickly and kills a significant number of the people it infects.

It is gratifying to have a vaccine that holds great promise for protection of humans
Dr Peter Jahrling
There is no treatment for the disease, so preventing the spread of the virus is key to containing outbreaks.

The research is the result of collaboration between teams of scientists at the Dale and Betty Bumpers Vaccine Research Center and the US Army Medical Research Institute of Infectious Diseases.

Two-stage process

The researchers have been trying to perfect a two-stage approach to developing vaccines for a range of infectious diseases.

The first stage involves an injection of non-infectious genetic material from the disease-causing microbe to trigger an initial response from the immune system.

This is then followed up several weeks later by a second injection, this time of a weakened carrier virus containing key genes from the microbe. This second jab is designed to substantially boost the initial immune response.

But the scientists realised that Ebola is such a virulent disease that time is of the essence if it is to be successfully combated.

So they decided to concentrate on the second stage of the process alone.

Eight monkeys were given a shot of a booster jab, and then injected with the Ebola virus.

The researchers found the single injection completely protected all eight animals against Ebola infection - even those who received high doses of the virus.

Researcher Dr Peter Jahrling said: "After years of developing candidate Ebola vaccines that protected rodents but failed in primates, it is gratifying to have a vaccine that holds great promise for protection of humans.

"Eventually, this vaccine may reduce the hazard of working with Ebola virus in the laboratory, as well as provide protection to populations at risk of natural exposure."

Ring vaccination

If the vaccine proves to be effective in humans, it could be used to block the spread of disease using a strategy known as ring vaccination - a technique which has been successfully employed in the past to stop the spread of smallpox.

It involves vaccinating everyone who has been in contact with a person who has the disease and all members of that person's household.

The strategy not only protects people who may have been exposed to the virus but also creates an added barrier of immunity around them, thereby protecting the entire community.

Researcher Dr Gary Nabel said even if the boost jab alone proved effective, there would still potentially be a role for the two-stage jab, as it elicits a stronger immune response.

"It may be useful for preventive vaccines intended for hospital workers at high risk of exposure to the virus, for example."

The research is published in the magazine Nature.

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