GALVESTON, Texas, July 14 (UPI) -- One dose of an inhalable Ebola vaccine was enough to protect monkeys exposed to 1,000 times the fatal Ebola dose from being infected by the disease, according to a new study.
An inhalable version of the vaccine means that highly trained medical personnel would not be necessary to distribute it, however researchers remain cautious because one vaccine this year already was shown to have no effect on humans despite working well in primates.
"This is a positive step forward," Dr. Daniel Bausch, a virologist from Tulane University, told the New York Times. "It's not a breakthrough or 'Eureka!' "
In the new study, published in the Journal of Clinical Investigation, researchers gave the vaccine to 10 rhesus macaques -- 4 received one dose, 4 received two doses, and two were given the vaccine in a liquid form -- and gave nothing to 2 more as a control group. Four weeks after the monkeys were vaccinated, they were injected with 1,000 times the dose of Ebola considered fatal.
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Within about a week, the two unvaccinated monkeys died, but the 10 who'd received the vaccine either in aerosol or liquid form survived and, after being euthanized, showed no presence of Ebola in their blood or tissues.
Researchers compared the effects of the aerosol and liquid forms as well, finding that the aerosol appeared to induce a stronger immune response in the respiratory tract than the liquid form. Because Ebola, which can be spread through the air, often enters the body through the lungs and respiratory system, the extra protection from the virus there is seen as important to its efficacy.
Michelle Meye, a postdoctoral fellow in the pathology department at the University of Texas Medical Branch said that a needle-free, inhalable vaccine offers advantages over other forms of delivery because it would not require medically trained personnel.
"This study demonstrates successful aerosol vaccination against a viral hemorrhagic fever for the first time," said Alex Bukreyev, a professor and virologist at UTMB, in a press release. "A single-dose aerosol vaccine would enable both prevention and containment of Ebola infections, in a natural outbreak setting where healthcare infrastructure is lacking or during bioterrorism and biological warfare scenarios."
The successful results of the test in primates will allow researchers to begin moving toward a clinical study in humans, they said. They remain cautious, however, because one Ebola vaccine this year has already failed to work in humans after a successful test with primates.
