After initially setting out to test two vaccines on 28,000 volunteers during West Africa's deadly Ebola epidemic, a U.S.-Liberia research team had to dramatically reduce its aspirations when the outbreak started coming to an end. But the investigators have now published results showing the shots from GlaxoSmithKline and Merck elicited antibody responses that lasted one year after vaccination.

For the phase 2 study, 500 participants received GSK's shot, 500 received Merck's vaccine and 500 got a placebo. At one week, researchers documented "modest" responses that ended up growing significantly by the one-month point, according to a new release. After a month, 71% of recipients of the GSK vaccine developed an antibody response to Ebola, compared to 84% of those who received Merck's vaccine and 3% for placebo.  

Antibody responses stayed strong to the one-year point: 64% for GSK's vaccine, 80% for Merck's and 7% for placebo. The National Institute for Allergy and Infectious Diseases (NIAID) sponsored the study while GSK and Merck provided vaccine doses.

Formed in 2014, a U.S.-Liberia partnership called Prevail conducted the work and had to scale down the study considerably—from an initial enrollment goal of 28,000 participants—as the outbreak came to an end in 2015. Instead of testing for efficacy, researchers had to adapt and instead examine antibody responses.

Interestingly, the groups who received the vaccines experienced fewer malaria cases than the placebo group, with the finding more pronounced for Merck's shot. That potential effect will need more testing, the group said.

Published in the New England Journal of Medicine, the findings are another step forward toward the goal of developing an effective Ebola vaccine. In a statement, NIAID director Anthony Fauci said a "safe and effective vaccine would be a critically important addition to classical public health measures in controlling inevitable future Ebola outbreaks.”

The results come right on the heels of the U.S. government's announcement it would contribute more development funds and potentially purchase doses of two promising shots, the Merck vaccine and another from Johnson & Johnson. Merck previously touted phase 1b results showing responses from its vaccine last at least a year.

Before that study, Merck's vaccine posted 100% efficacy in a novel "ring study" that didn't incorporate a placebo arm. For the trial, done in Guinea, researchers sought to create a "ring" around documented Ebola cases to stop the virus' spread with vaccinations. Investigators found that vaccinated groups didn't experience any new cases.

Recent Ebola and Zika outbreaks have made it abundantly clear for vaccine experts that changes need to be made to the emerging disease vaccine R&D model. Many governments, pharma companies and nonprofits came together recently to form the Coalition for Epidemic Preparedness Innovations that will proactively fund and work on vaccines against future threats.