British drugmaker GlaxoSmithKline will start clinically testing an Ebola vaccine as international health workers struggle to contain an outbreak of the deadly disease.

Glaxo will partner with the National Institutes of Health (NIH) to start a Phase I trial, giving the vaccine to a limited number of patients to test its effectiveness, in the next few months.

“In collaboration with the Vaccine Research Center at the NIH, we have evaluated this vaccine candidate in pre-clinical studies and we are now discussing with regulators advancing it to a phase I clinical trial programme later this year,” Glaxo announced in a statement on Monday.

But the company warned that the vaccine tests will take years.

“Clinical development for a new vaccine is a long, complex process, often lasting 10 or more years,” the company cautioned.

An Ebola outbreak in Sierra Leone, Guinea, Liberia and Nigeria has killed nearly 1,000 people so far, and more than 1,800 cases of the disease have been reported by the World Health Organization.

According to the NIH, the Glaxo vaccine has already shown promise in primates. The vaccine is so early in the clinical trial stage it has not yet been given a name.

If the initial trial is successful, Glaxo can begin testing the vaccine in Phase II trials with a larger population. A timeline, though, has not been set for completing Phase I.

Depending on the success of the first trial, the vaccine could undergo an accelerated approval process by the Food and Drug Administration because of the great need for a vaccine.

In the meantime, people at risk for contracting Ebola could be allowed to use the vaccine on compassionate grounds before the drug is fully tested and approved.

The NIH is also working with Crucell, a subsidiary of Johnson & Johnson, to develop another Ebola vaccine. That vaccine isn’t expected to be available for clinical trials until late 2015 or early 2016.

Recently, two American missionaries who contracted Ebola in Liberia were treated with an experimental drug, ZMapp, and flown back to the U.S. for further treatment.

The fact they were given the experimental drug while hundreds of other African health workers are dying in the outbreak has raised moral and ethical questions about the decision.

President Obama has said it is too soon to fast-track ZMapp for approval, arguing that there is not yet enough research to determine whether the vaccine is effective and safe.

Obama said the focus should be on helping countries affected by Ebola improve their healthcare infrastructure to fight the outbreak.