Study evaluates effectiveness of experimental Ebola vaccine following high-risk exposure

March 31, 2015

A new vaccine could be capable of preventing Ebola after a needlestick injury has been sustained. The innovative injection has been the focus of a new study, published in the Journal of the American Medical Association (JAMA), which is trying to determine how effective it could be for preventing the disease.

One physician who received an experimental Ebola vaccine after experiencing a needlestick injury when in Sierra Leone did not develop the disease, despite there being strong immune responses that are specific to Ebola. However, because of its limited use, the evidence supporting the validity of the vaccine is lacking.

This is according to the latest JAMA study, which focused on an American physician who was working in an Ebola treatment centre in West Africa. The 44-year-old experienced an accidental needlestick injury, which posed a significant risk of infection.

Given the severity of Ebola, he was offered experimental postexposure vaccination, which he gave his consent for. The vaccine is currently in clinical trials in the region and was given 43 hours after the initial exposure. The patient then returned to the US and received the vaccine intramuscularly.

Dr Mark Mulligan, from Emory University, Atlanta, and colleagues assessed the patient's response to the vaccine, said, during the 12-hour period after the vaccination, he developed malaise, nausea and fever.

The physical exam in the US, approximately 14 hours after the exposure, indicated that he was in mild to moderate distress from the fever, nausea, malaise and myalgia. By the second day, his fever had declined but he still had severe symptoms. Between three and five days after the exposure, the patient experienced resolution of symptoms and laboratory abnormalities. A week after the incident he was displaying no symptoms of the condition.

Blood tests detected Ebola virus glycoprotein-specific antibodies and strong Ebola-specific adaptive immune responses. 

"The clinical syndrome and laboratory evidence were consistent with vaccination response and no evidence of Ebola virus infection was detected," the authors write.

"In the current patient, a self-limited, moderate to severe clinical syndrome began at 12 hours postvaccination. Future decision making about using this experimental vaccine for postexposure vaccination will need to balance the risks of harm from the vaccine or possible Ebola infection (both were unknowns at the time of the patient's exposure) against the possible benefit of vaccination (also unknown at the time of the patient's treatment)."

They add that the efficacy of the novel vaccine for postexposure protection cannot be learned from this single case, but the clinical and laboratory parameters are informative at a time when there is a need to garner all information available on Ebola vaccines.

Writing in an accompanying editorial about the study, Dr Thomas W. Geisbert, of the University of Texas Medical Branch, Galveston, said the most effective way of preventing and controlling outbreaks is to protect high-risk personnel, such as healthcare workers.

Related Clinician and Patient Safety: