Read Jon Cohen’s piece in Sciencemag that underlines that there is no data showing the safety or efficacy of Merck’s Ebola vaccine, which is why regulatory bodies have not licensed it.
“The unusual trial design yielded data that were not deemed strong enough to lead regulatory bodies to license the vaccine, but they went a long way toward convincing the world that an Ebola vaccine is at hand—and that it might have the power to prevent future outbreaks from ever becoming this big again,” he writes.
In short, Jon Cohen says that the vaccine is part of a PR stunt designed to deceive the world into thinking there is a safe and effective Ebola vaccine.
“And a careful examination of the data so far—supported by dozens of interviews with the leaders of the studies and other Ebola experts—makes it clear that almost every other trial seems destined to end in questionable results or outright failure. Findings from those that have ended are proving difficult to publish in top-tier journals.
The reasons are varied and complicated. Even under the best circumstances, clinical trials don’t always deliver satisfying results. In this case, many studies started too late, when the epidemic was already declining, and ran out of patients. Others had designs that from the outset had little chance of providing a clear answer. A pharmaceutical company aborted a trial for reasons it never clarified, and the fate of another trial remains obscure even to the World Health Organization.
On 26 September 2014, the U.S. Centers for Disease Control and Prevention (CDC) released a projection that shocked the world. Based on its epidemiologic models, CDC estimated that if the lackluster response to the Ebola epidemic continued unchanged, Sierra Leone and Liberia alone could have up to 1.4 million cases by January. A vaccine seemed the only hope to avert this catastrophe.
GlaxoSmithKline (GSK) and Merck raced forward with tests of two vaccines in the affected countries. Each has the Ebola virus surface protein gene stitched into a harmless viral “vector”: GSK uses a chimpanzee adenovirus, whereas Merck relies on a livestock pathogen called vesicular stomatitis virus (VSV). But by February 2015, when the first large-scale vaccine trials began, the model had been proven misleading: The epidemic was petering out because of ramped-up containment efforts. Cases became so rare in Liberia that it had to downgrade a phase III trial of both vaccines to phase II after enrolling a mere 1500 of an anticipated 27,000 participants.
As a result, there is no verdict on the efficacy of the GSK vaccine. But the VSV vaccine had another shot at proving its worth. In a move that yielded the only solid success of any Ebola trial, an international consortium led by the World Health Organization launched a test of the Merck vaccine in Guinea with a novel design, which gleaned results even as cases dwindled. Instead of the traditional vaccine trial that randomly assigns people to receive a shot or a placebo, this study used a design called ring vaccination, following the epidemic where it went. It targeted clusters of people who had been in contact with a confirmed case, as well as the contact’s contacts, and compared them with similar clusters that did not receive the shots until 3 weeks later.
On 31 July, the researchers announced that the trial was a stunning success: No one who received the vaccine developed the disease 10 days or more after the shot—presumably the length of time it takes to develop immunity. In the clusters that had to wait for the vaccine, 16 people contracted Ebola.
The unusual trial design yielded data that were not deemed strong enough to lead regulatory bodies to license the vaccine, but they went a long way toward convincing the world that an Ebola vaccine is at hand—and that it might have the power to prevent future outbreaks from ever becoming this big again.