Ebola Vaccine Trials May Be Limited by Waning Epidemic

Experimental Ebola vaccines to be tested in West Africa may go through an alternative path for U.S. regulatory approval because a waning epidemic is making it difficult to collect the full array of data normally gathered in clinical trials.

The vaccines, developed by the U.S. National Institutes of Health, GlaxoSmithKline Plc, Merck & Co. and NewLink Genetics Corp., may be filed to regulators using human safety and immune response results from trials in Liberia and Sierra Leone, together with efficacy data from earlier animal studies, National Institute of Allergy and Infectious Diseases Director Anthony Fauci told reporters on a conference call. Regulatory approval of new drugs usually requires both safety and efficacy data in humans.

“We are trying to prove the efficacy of a vaccine in a trial in which there are infections,” Fauci said. “But if the infections disappeared in a few weeks, the data you get on safety and immunogenicity could be very important for alternative regulatory approval.”

Vaccine makers have been rushing for months to ready the world’s first Ebola shots in an effort to curb the deadly outbreak, which has infected more than 21,000 people and taken almost 8,700 lives. Glaxo said the first batch of its vaccine is being shipped to West Africa, and an initial 300 vials will arrive in Liberia later today.

Testing Strategies

As infection rates in Liberia, Sierra Leone and Guinea are declining, public health officials are shifting strategies to move ahead with testing vaccines. Only eight cases of Ebola were reported in Liberia last week, compared with more than 200 a week in September. Guinea reported 20 cases, while Sierra Leone remains the worst-affected country with 117 cases last week.

A late-stage trial of the Ebola vaccines with 27,000 participants may begin in Liberia within the next few weeks and may last up to a year, Fauci said. Health officials in Liberia and Sierra Leone have also raised the possibility of collaborating to spread the trial between the two countries, he said.

While the U.S. Centers for Disease Control and Prevention plans to conduct a separate trial in Sierra Leone, it is still awaiting data from early-stage trials to decide which vaccine to test, said Anne Schuchat, director of the National Center for Immunization and Respiratory Diseases at the CDC.

A waning epidemic means more participants are needed to make the trials statistically robust, and the trial in Sierra Leone may be expanded beyond the original plan for 6,000 participants, Schuchat said.

J&J’s Vaccine

Johnson & Johnson, which is planning to start late-stage trials of a combination vaccine it’s developing with Bavarian Nordic A/S by April, may need 30,000 to 100,000 participants -- or even significantly more -- to make the results statistically meaningful, Paul Stoffels, J&J’s chief scientific officer, said in an interview last week.

“Whether we will be able to get a study where we can get a statistical end-point showing efficacy, we don’t know, but we’ll do our best,” Stoffels said. “That may require much larger clinical trials, and we are set up to do that.”

J&J has said it has already produced more than 400,000 doses of its prime-boost vaccine combination, and a total of 2 million doses may be available over the course of the year.

Glaxo has said it may be able to produce a million doses a month of its Ebola shot by December.

(An earlier version corrected which product the U.S. is considering for early approval in first and second paragraphs.)

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