Canadian and World Health Organization officials have yet to work out the myriad details of how and where to send a shipment of experimental Ebola vaccinations – meaning it may take considerably more time to get the vaccine in the hands of front-line health workers fighting the largest Ebola outbreak in history.

"Discussions with the Canadian [government] are likely to continue for a while before anything concrete is known," said Gregory Hartl, a spokesperson with the WHO.

Mr. Hartl could not yet say when the Canadian-donated vaccine shipment is likely to arrive, where it is likely to be deployed first or to whom.

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In the meantime, more and more relatively untested, experimental Ebola treatments are starting to arrive in West Africa, where the disease has killed more than 1,000 people and prompted health officials to temporarily set aside traditional rules about using experimental medication on humans.

Nigeria's health minister announced on Thursday that the country will begin using another experimental drug called Nano Silver to treat some of the eight Nigerian residents who have Ebola. Little is known about Nano Silver, which, like several other Ebola treatments, is largely untested on humans. The minister said the drug was developed by a Nigerian scientist, but would not give the scientist's name.

A small shipment of another experimental Ebola treatment called ZMapp has also arrived in West Africa. The drug, developed by a San Diego-based pharmaceutical company, will be used to treat patients in Liberia.

The Liberian shipment contains only about a dozen doses of ZMapp, raising difficult questions as to who should be treated first – in addition to ongoing questions about the experimental drug's safety and effectiveness when used on humans.

Officials with the WHO and elsewhere have now largely determined that deploying experimental vaccines and treatments is likely to do more good than harm, given the massive scale and mortality rate of the ongoing Ebola outbreak. But the health agency is far less clear on how to prioritize treatment.

"These are slippery slope issues," said Mark Bernstein, a professor of surgery at the University of Toronto and a neurosurgeon and bioethics researcher at Toronto Western Hospital. "Generally in medical care, the resources are given to those who are most needy – if an alcoholic is sicker than the King of England and you have one operating room, the sicker patient gets it."

But so far, many of the early treatments have been administered to foreign front-line health workers who have become infected during the course of their work, rather than any of the patients living in the outbreak areas.

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Further complicating matters is the fact that even a purely severity-based model of prioritization may prove ineffective. Many of the experimental drugs have been shown to work most effectively on patients who are only a few days removed from the moment of infection. As such, administering the drugs to patients who are much sicker and further along in the infection may prove a waste of resources, as those patients end up dying anyway.

In order to understand whether the many experimental treatments are actually working, the WHO declared this week that "there is a moral obligation to collect and share all data generated, including from treatments provided for 'compassionate use' [access to an unapproved drug outside of a clinical trial]."

It is not yet clear whether that guideline will require any Canadian health agencies to monitor the efficacy of the donated vaccine. Usually, a vaccine is used to prevent future infections in otherwise healthy patients. But because the Canadian vaccine has been shown in some animal tests to offer protection even after the infection takes place, and because the current outbreak is so dire, it is possible that the vaccine may be used as a form of treatment as well as inoculation.

A spokesman for the Public Health Agency of Canada could not provide answers on Thursday to the questions of when the vaccine is expected to arrive in the hands of the WHO, whether Canada is working with the WHO to determine who will get the vaccine first or whether any Canadian agency will monitor the effects of the vaccine when it is finally administered.

More than 1,000 people have died so far from this year's Ebola outbreak in West Africa. Here, we map out all deaths up to and including Aug. 11.