New Ebola vaccine safe, stimulates strong immune response

A clinical trial of a new Ebola vaccine has found that it is well tolerated and stimulates strong immune responses in adults in Mali, West Africa and in the US, scientists say.

If the vaccine called ChAd3-EBO-Z is ultimately found to be safe and effective, it could offer crucial protection for contacts (family members, neighbours, etc) of patients with confirmed Ebola disease in future epidemics, thereby helping to interrupt transmission.

The study, carried out in Mali, West Africa and Baltimore in US, included the first testing of this vaccine in adult health care workers and other at-risk persons in Africa.

It identified the dose to be used in subsequent clinical trials and for large-scale manufacture of the vaccine.

Researchers said that if larger trials corroborate the vaccine's clinical acceptability and immunogenicity, and with evidence of protection from future field trials or from non-human primate challenge models, the vaccine could obtain regulatory approvals to become a tool to interrupt transmission in future outbreaks.

This would be achieved by vaccinating all people who have come into contact with confirmed Ebola cases.

Researchers also found that the administration of a booster vaccination with another vector vaccine producing Ebola virus antigens led to further enhanced immune responses likely to be associated with long-lived protection.

This "prime-boost" approach provides a way to vaccinate health care workers and other front-line workers who live in areas where Ebola poses a threat to re-emerge and who need prior enduring protection.

The trial was carried out by a group of researchers within the Centre for Vaccine Development (CVD) of the University of Maryland School of Medicine (UM SOM), collaborating closely with researchers from the Centre for Vaccine Development of Mali (CVD-Mali).

"This is a crucial step on the road to using this vaccine in humans," said Dr Myron M Levine from UM SOM.

"This gives us essential information that the vaccine is not only well-tolerated but the high dose stimulates strong immune responses in adults in West Africa, the global region where the Ebola outbreak was rampant last year," said Levine.

The vaccine consists of an adenovirus (cold virus) that has been modified so that, in humans, it does not cause illness and cannot multiply.

It does not contain the entire virus, but a single Ebola protein. Immune responses directed against this attachment protein have been shown to be highly protective in animal studies.

The study was the result of a consortium of the World Health Organisation (WHO), the Vaccine Research Centre (VRC) of the National Institute of Allergy and Infectious Diseases (NIAID), the Jenner Institute at the University of Oxford, CVD-Mali, CVD-UM SOM, and GSK Biologicals (manufacturer of the vaccine).

The study was published in the journal Lancet Infectious Disease.