WASHINGTON, March 14 (Xinhua) -- A two-vaccine regimen intended to protect against the deadly Ebola virus induced a durable immune response in 100 percent of healthy adult volunteers one year after vaccination, results from a phase one clinical trial showed Tuesday.
Ebola virus disease is a severe, often fatal illness in humans. The virus is transmitted to people from wild animals and spreads in the human population through human-to-human transmission.
The new study, published in the Journal of the American Medical Association, involved two vaccine candidates, one used to stimulate or "prime" an initial immune response, and a second used to boost the body's response.
The trial was conducted by researchers at the University of Oxford, who enrolled healthy participants aged 18 to 50 in the United Kingdom.
Participants were selected randomly to receive either the two-vaccine regimen or saltwater injections.
Of the 75 participants who received the vaccine regimen, 64 remained in the study for a follow-up visit on day 360.
No serious vaccine-associated adverse events were observed, and all of the active vaccine recipients maintained antibodies to Ebola virus at day 360.
This is "the longest duration follow-up for any heterologous primary and booster Ebola vaccine schedule to our knowledge," the researchers wrote in their paper.
They added that the two-vaccine strategy "may offer advantages over reactive use of single-dose vaccine regimens" in at-risk populations, where durability of immune response is likely to be of primary importance.
Johnson & Johnson, which developed the prime vaccine, said in a statement that a total of 10 clinical studies for the Ebola vaccine regimen are currently being conducted on a parallel track across the U.S., Europe and Africa.
Meanwhile, the company said it, in partnership with Bavarian Nordic, which developed the booster vaccine, rapidly scaled up production of the vaccine regimen and now has approximately 1,8 million regimens available, with the capacity to produce several million regimens if needed.
Besides the investigational prime-boost vaccine regimen, rVSV-EBOV, an experimental Ebola vaccine developed by the Public Health Agency of Canada, has already proven highly effective against the deadly virus during a major trial in Guinea, the World Health Organization said last year.