Investigators have temporarily halted a trial of NewLink Genetics’ experimental Ebola vaccine after several patients reported unexpected side effects.

While most of the 59 volunteers tolerated the injection well, with only a few anticipated mild fevers or muscle aches, four patients reported joint pains in their hands and feet, the University Hospital of Geneva, one of several sites testing the vaccine, said.

The temporary interruption of a clinical trial is a standard precautionary measure in such cases, according to officials. While investigators were not concerned that the joint pains were serious, the trial’s data safety monitoring board elected to pause the trial until Jan. 5 to collect more information on these effects and share that information with other trial sites in the U.S., Canada, Germany and Gabon.

If researchers are eventually able to conclusively link the joint pains to the vaccine, however, this would need to be explained to other trial volunteers, the hospital says.

Going forward, patients will be given a lower dose, said Pamela Eisele, a spokeswoman for Merck, which recently licensed the vaccine from NewLink.

The VSV-ZEBOV vaccine, which was originally developed by the Public Health Agency of Canada, is in Phase I testing. If all goes well, the National Institutes of Health plans to conduct a Phase III trial early next year to evaluate the vaccine’s safety and efficacy. — Lena Freund

Originally appeared in Drug Industry Daily, the pharmaceutical industry’s number one source for regulatory news and information. Click here for more information.