Ebola Vaccine Safe, Study Demonstrates

A clinical trial of a new Ebola vaccine (ChAd3-EBO-Z) that resulted from an unprecedented global consortium assembled at the behest of the World Health Organization has found that it is well tolerated and stimulates strong immune responses in adults in Mali, West Africa and in the United States.

A clinical trial of a new Ebola vaccine (ChAd3-EBO-Z) is showing that it is well tolerated and stimulates immune responses in adults in Mali, West Africa and in the United States, according to a study published in the journal Lancet Infectious Disease

If the vaccine is ultimately found to be safe and effective, it could offer crucial protection for contacts (family members, neighbors, etc.) of patients with confirmed Ebola disease in future epidemics, thereby helping to interrupt transmission. Larger trials of the vaccine sponsored by GSK Biologicals have already begun.

The study, carried out in Mali, West Africa and Baltimore, included the first testing of this vaccine in adult health care workers and other at-risk people in Africa. It identified the dose to be used in subsequent clinical trials and for large-scale manufacture of the vaccine. 

The researchers noted 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 faculty researchers within the Center for Vaccine Development (CVD) of the University of Maryland School of Medicine (UM SOM), led by Milagritos D. Tapia, MD and Kirsten Lyke, MD, collaborating closely with Professor Samba O. Sow, MD, MSc. 

“This is a crucial step on the road to using this vaccine in humans,” Dr Levine said in a press release. “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.”

The vaccine consists of an adenovirus 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 (which are carried out under the highest level of physical containment).

The study compared the clinical acceptability and immune responses of 20 adult participants in Baltimore and 91 in Mali; each group was given different dosage levels of vaccine. The study found that there were no safety concerns, and recommended that further studies be carried out.


1. Tapia  MD, Sow SO, Lyke KE, et al. Use of ChAd3-EBO-Z Ebola virus vaccine in Malian and US adults, and boosting of Malian adults with MVA-BN-Filo: a phase 1, single-blind, randomised trial, a phase 1b, open-label and double-blind, dose-escalation trial, and a nested, randomised, double-blind, placebo-controlled trial. Lancet Infect Dis. 2015;DOI: http://dx.doi.org/10.1016/S1473-3099(15)00362-X.