Novavax Inc.'s Ebola vaccine helped healthy people develop an immune response against the deadly virus in an early trial.

In a randomized study compared against a placebo, the vaccine pushed participants' immune systems to build up antibodies to fight Ebola when combined with a supplement to boost production of the proteins, according to Greg Glenn, Novavax's head of research.

"We have a very, very robust immune response," Glenn said by phone. Monkeys who exhibited the same response to the vaccine "were completely protected" from Ebola. Novavax presented a study about the effect of the vaccine on primates in March.

Ebola ravaged West Africa beginning in early 2014, killing more than 11,000 people. While the disease has fallen off sharply, stubborn pockets persist, with 30 new confirmed cases in the week ended July 12. Several potential vaccines -- from companies including GlaxoSmithKline Plc, Merck & Co. and NewLink Genetics Corp. -- are being tested on humans.

The Novavax study also found that its vaccine was "well-tolerated" and safe, Glenn said, with minor side effects including headaches. The trial involved 230 healthy Australian adults.

Novavax shares have doubled this year, valuing the company at $3.3 billion. Novavax, which has its headquarters in Gaithersburg, Maryland, is also working on vaccines for respiratory syncytial virus, or RSV, as well as influenzas and the Middle East Respiratory Syndrome coronavirus, according to its website.

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