Referring to the Guinea clinical trials, a panel of experts convened by the US National Academy of Medicine, reported the following: "We concur that, taken together, the results suggest that the vaccine most likely provides some protection to recipients - possibly 'substantial protection,' as stated in the final report. However, we remain uncertain about the magnitude of its efficacy."
Further, they expressed some concern that early positive results might make it difficult to justify, on an ethical basis, controlled clinical trials of the vaccine in the future.
It also has to be made clear that people who already carry the virus are likely to develop an infection, even if they receive the vaccine.
Other concerns arise when new pharmaceuticals are tested in settings among vulnerable populations. As noted by Liberian academic Robtel Neajai Pailey, there is a history of medical experimentation among vulnerable populations in the US and parts of Africa.
Informed consent by research participants requires a complex negotiation under any circumstances, but the history of experimentation Pailey and others describe too often intensify community concerns and negative responses to certain medical interventions.
How will the questions about its efficacy be properly explained? Under what conditions can an "Ebola contact" refuse the vaccine? Under what conditions will the vaccine be contraindicated for people who have been close contacts with Ebola sufferers, and how will this be explained?
Recently, I sought personal accounts from clinical trial participants in Sierra Leone, where I work as an anthropologist. During those conversations, I learned second-hand about participants' inability to report concerning side effects of the vaccine - swollen joints and joint pain; skin lesions; and fever - to the research team.
How will those vaccinated understand their risk of infection and how will this shape their actions if the disease continues to spread? Who among close contacts will be missed through other means, if reports of Congolese communities' evasion of health workers are true?
In an interview with The Atlantic, Seth Berkley, the director of the NGO Gavi, which has supported the vaccination campaign, expressed concern that people who learn about possible Ebola infections among the vaccinated would lose confidence in the vaccine.
Beyond Ebola: The virus hunters
Confidence in the vaccine, however, may very well be the least of the global health community's problems. If serious, careful efforts to inform communities about the risks and pitfalls and limitations of the vaccine - and knowledge about all of these - are not made, lack of confidence in and mistrust of the health system may be difficult to overcome during future health campaigns like this one.
The introduction of this experimental Ebola vaccine - whatever its efficacy and potential risks - will inevitably shape the landscape of care and communities' trust of the health system, more generally.