Late Friday on the eve of the long Labor Day weekend, Sanofi announced it would suspend work on a candidate Zika vaccine that it has been developing with Walter Reed Army Institute of Research (WRAIR), based on news it received of scaled-back federal support.

Rocky vaccine landscape

After a surge of activity in the Americas, Zika activity has dropped off sharply this year, after tearing through populations who weren't exposed to it before who now are thought to have some protection based on herd immunity.

As with the 2013-16 Ebola outbreak, a steep drop in new cases poses obstacles to testing new vaccines and treatments. Though globally there are about 20 Zika vaccines at different stages of development, the Sanofi vaccine is one of a few at the advanced stage.

Vaccine efforts have been buffeted by other tough headwinds, such as political controversy over how Sanofi might price a vaccine developed with taxpayer funding. In February, a federal ethics panel rejected a proposal for human challenge studies with Zika virus, which would have offered the possibility of streamlining vaccine research and might have helped whittle the list of vaccine candidates down to the ones that would offer sterilizing immunity, important for curbing the risk of birth defects.

Federal reassessment

In July 2016, Sanofi—which has developed vaccines against other flaviviruses—agreed to license WRAIR's Zika purified inactivated virus vaccine and launch phase 2 clinical trials. WRAIR and the National Institute of Allergy and Infectious Diseases (NIAID) had supported the vaccine in phase 1 trials.

Last fall, Sanofi received a $43 million award from the US Department of Health and Human Services (HHS) Biomedical Advanced Research and Development Authority (BARDA) to speed the development of the vaccine. To streamline development, Sanofi had lined up Brazil's Fiocruz Institute as part of the team.

In its Sep 1 statement, Sanofi said BARDA informed the company on Aug 17 that the agency reassessed its Zika-related projects and have decided to focus on a more limited set of goals and deliverable, and that BARDA has decided to "de-scope" its contract with Sanofi for the manufacture and clinical development of an inactivated Zika vaccine.

BARDA said it would limit its funding to a case definition and surveillance study, as well as any activities needed to pause work on the vaccine until an epidemic re-emerges.

As a result, Sanofi said it doesn't intend to continue developing or seek a license from WRAIR for the Zika vaccine candidate.

It added that, with partial support from BARDA, the case definition and surveillance study is already under way in four locations—Colombia, Honduras, Mexico, and Puerto Rico—with the goal of enrolling 2,400 volunteers.

Sanofi said that adding its expertise to the Zika public health emergency cost the company other opportunities and reshuffled its priorities. "The epidemiology of the disease has changed significantly since that time, but we continue to believe that public-private partnerships are the right model to address these public health challenges and should continue to play a major role in response to emerging infectious diseases."

What's on the Zika horizon for BARDA?

BARDA Director Rick Bright, PhD, told CIDRAP News today that Zika is still a public health threat and that BARDA's plan is to continue working with industry partners, including Sanofi, on developing Zika vaccines and diagnostics to make them available commercially as quickly as possible.

"The specific activities of development projects often change bases on a variety of technical, business, and epidemiological factors," he said.

See also:

Sep 1 Sanofi statement

Oct 27, 2016, CIDRAP News story "Sanofi taps Brazilian researchers to speed Zika vaccine"