Human trials of an experimental vaccine for Ebola is expected to begin this week in the US and later in the UK and Africa.
The experimental Ebola vaccine similar to one being developed by GlaxoSmithKline is effective for at least five weeks in lab monkeys but requires boosting with an additional vaccine to extend its protection to 10 months, according to a study published on Sunday.
The findings offer an early hint of which, if any, of the Ebola vaccines in development will prove effective, and in what form. Johnson & Johnson and NewLink Genetics are also among the firms accelerating their efforts to provide Ebola vaccines and treatments as the worst known outbreak of the virus ravages West Africa, killing more than 2,000 people.
The results of the new study suggest, for instance, that a GSK vaccine now being tested on healthy volunteers will protect against Ebola infection in the short term, but may have to be augmented for long-term protection.
The study, published in Nature Medicine, is the first to report that a vaccine regimen produced “durable immunity” against Ebola, protecting four out of four monkeys for 10 months.
The vaccine uses a chimp adenovirus, closely related to a human version that causes upper respiratory tract infections, into which scientists spliced an Ebola gene.
The adenovirus infects cells in a vaccinated animal, causing them to take up the gene and produce Ebola proteins. That primes the immune system to attack the proteins of Ebola viruses when an infection occurs.
The vaccine in the study is similar to competing vaccines being developed by GSK, which began human safety trials last Tuesday, and by J&J, which aims to start safety trials in early 2015.
A third experimental Ebola vaccine uses a different delivery system, a livestock pathogen called vesicular stomatitis virus (VSV). A version developed by the Public Health Agency of Canada and licensed to NewLink Genetics is scheduled to be tested for safety in healthy volunteers this fall. Profectus BioSciences is also developing a VSV vaccine.