Two Ebola vaccine candidates might be ready for testing in hard-hit West African countries in December, a month earlier than previously predicted. And one vaccine manufacturer has said it may have millions of doses available by April, should studies prove that it’s safe and effective, a much more optimistic scenario than outlined until now.

As more and more resources are mobilized for development of Ebola vaccines, the timeline is being compressed, said Marie-Paule Kieny, an assistant director-general at the World Health Organization (WHO), today at a press conference about a high-level meeting on vaccines that took place yesterday. “Things are changing from week to week,” said Kieny, who also noted that several new donors have offered to help finance vaccine production and testing. Two new Ebola cases, one in Mali and one in New York City, have added to the sense of urgency in containing the spread of the deadly virus. But the best-case scenarios being discussed may be far too optimistic given the rapid spread of the Ebola virus, particularly in Liberia, Sierra Leone, and Guinea.

The focus of the meeting was “access and financing” of the vaccines, which many workers in the field initially thought could not be developed quickly enough to help with this epidemic. But as the epidemic continues to grow—there are nearly 10,000 officially reported cases to date, about half of whom have died—efforts to speed the testing and production of vaccine have gained steam, and this was the latest of several related WHO meetings. (ScienceInsider described some of the meeting’s key talking points yesterday based on leaked documents from the meeting; the documents were originally distributed to participants, who included scientists and representatives from companies, governments, and regulatory agencies.)

In a few weeks, meeting participants learned, enough data may be available from small phase I trials of a vaccine jointly made by the U.S. National Institute of Allergy and Infectious Diseases and GlaxoSmithKline (GSK) that began in September to launch efficacy studies. A second vaccine, initially developed by the Public Health Agency of Canada and now made by NewLink Genetics of Ames, Iowa, that started phase I trials in October might have similar data available by December. Efficacy trials may test both vaccines simultaneously. But the looming question has been how much of these products will be available should they prove effective, which could be known as early as April.

Both GSK and NewLink Genetics said at the meeting that they might be able to produce far larger quantities of their vaccines than they initially estimated. GSK said it could have 230,000 doses available in April, and could—if it had financing—produce more than 1 million doses a month by December 2015. This would be far short of what’s needed in the three hardest hit countries in West Africa, which have a combined population of nearly 22 million. In its most optimistic scenario, NewLink Genetics said it could have 12 million doses of its vaccine ready by April (see table below).

NewLink Genetics presentation at WHO meeting

NewLink Genetics offered production estimates based on different doses of its vaccine.

The amount of the NewLink vaccine that will be available will depend heavily on how much of the vaccine material is needed to constitute a “dose” that can safely teach the immune system how to thwart Ebola virus. The ongoing phase I studies should help clarify this question. If the highest dose is needed, 100 million virus particles, the company would have only 125,000 doses ready by April. But if the necessary dose is only 1 million virus particles, 100 times as much could be available, NewLink noted in a presentation made at the meeting. Kieny stressed to ScienceInsider that “it’s not clear at this moment whether [the lower dose] will be sufficient.”

Ira Longini, an epidemiologist at the University of Florida in Gainesville who attended the meeting, says dosing decisions may yet delay the NewLink vaccine. Despite the optimistic prediction, he cautions that it may not be ready for testing in an efficacy trial that starts in December.

Liability issues loom large, too, noted meeting participant John-Arne Røttingen, director of the Norwegian Institute of Public Health’s Division of Infectious Disease Control in Oslo. Some suggested liability should be handled similarly to the H1N1 influenza vaccine, which was made quickly to combat that pandemic in 2009. For that vaccine, drug manufacturers took responsibility for product quality, but countries covered liability for its use. That model may not be appropriate, others said, as the H1N1 vaccine was a variation on the well-established influenza vaccine formula; more unknowns—and thus more risk—surround these Ebola vaccines. Still, Røttingen says, “There seems to be a convergence to establish a group that would finance and pay for vaccines and should also take responsibility for liability issues in cooperation with affected countries.”

Several countries and organizations at the meeting offered to help support development and testing of the vaccines, Kieny said. Doctors Without Borders pledged to start a fund if necessary, and a few governments and the World Bank also pledged to help finance the efforts. GAVI, the Vaccine Alliance, a public-private partnership that bankrolls the majority of vaccines in developing countries, might play a big role as well. Keiny noted that GAVI representatives “are working on a proposal that they would put to their board.” The GAVI board plans to meet in December.

*The Ebola Files: Given the current Ebola outbreak, unprecedented in terms of number of people killed and rapid geographic spread, Science and Science Translational Medicine have made a collection of research and news articles on the viral disease freely available to researchers and the general public.