Workers train with protective equipment for handling Ebola-infected patients (Photo by CDC Global, CC license)

The 2014 outbreak of Ebola was one the largest and deadliest brushes with the frightening virus in history, and has spurred unprecedented efforts to develop a working vaccine. Until such a vaccine can be developed and reliably produced, populations in the outbreak epicenter—and medical providers who are assisting them—are working without a net, so to speak.

In late September of last year, Dr. Lewis Rubinson fell off the tightrope. While working at a clinic in Sierra Leone, Rubinson accidentally stuck himself with an infected needle; He let the stick site bleed to promote flushing and, while the clock ticked down until the decontamination procedures were complete, he washed the area with a diluted bleach solution—the only decontamination solution at hand. No one, least of all Rubinson himself, imagined that it would be very effective at preventing an infection if the needle had been truly contaminated.

Although vaccine research and production had been extremely limited before the outbreak, the Canadian National Microbiology Laboratory had developed an experimental vaccine called VSV-ZEBOV, which they produced around 1500 doses of prior to the outbreak. One of those was administered to Dr. Rubinson before the jet he chartered left for the National Institutes of Health Special Clinical Studies Unit (SCSU) in Bethesda, Maryland.

The SCSU has hosted a number of America's Ebola patients, and as Rubinson's temperature spiked and he began to experience nausea, malaise, and chills, the symptoms looked very familiar. But after three days, the fever and other symptoms began to subside. By day seven, Rubinson was completely symptom-free.

Researchers have since concluded that the Ebola-like symptoms were in fact caused by the VSV-ZEBOV vaccine. But whether or not the vaccine prevented him from developing Ebola is a question that can never be answered (at least not yet).

Ebola virus - (Photo by CDC)

VSV-ZEBOV is designed to trick the immune system into producing antibodies that effectively fight against Ebola. This is accomplished by taking a relatively benign virus—vesicular stomatitis virus, in this case (hence the VSV)—and coating it with cell receptors similar to those found on the outside of the Ebola virus. This approach is only one of several avenues of exploration toward an effective Ebola vaccine, but none have been conclusively proven effective for human subjects.

The efficacy of vaccines is difficult to establish on a case-by-case basis, and until the massive Ebola outbreak occurred, there was no way to test them in the numbers required to prove they work. Moreover, testing a new vaccine often carries a risk in and of itself—Rubinson's symptoms are only a hint of what can happen when vaccines go wrong. When contracting the major disease they are designed to prevent is itself a low-likelihood occurrence, large-scale testing may be unethical.

Unfortunately, without that testing, when a disease outbreak changes that equation, the vaccines won't be ready to go.

Rubinson's use of VSV-ZEBOV is one valuable data point about the vaccine but it is about to get many more as a large-scale trial is about to begin in Guinea. Although availability is still limited, researchers plan to make the most of what they have by using a "ring" strategy similar to methods used in the eradication of smallpox. The technique calls for identifying new cases and swiftly inoculating any person who might have come into direct contact with the infected patient. The test could serve the dual purpose of validating the vaccine in an environment where it can be effective and simultaneously helping to squelch the outbreak.

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