Trouble mounts for Sanofi dengue vaccine over safety concerns

The World Health Organization said on Monday it hopes to review safety data on Sanofi’s dengue vaccine this month, while the Philippines ordered an investigation of its now suspended massive immunization program after the French drugmaker said it could actually worsen the disease in some cases, reports Reuters.

The safety fears involve possible increased risk to people who had not previously been exposed to the dengue virus prior to vaccination with Dengvaxia.

Sanofi SA (SASY.PA) attempted to allay concerns, saying in a statement that “the vast majority of those vaccinated to date live in high endemic settings and, therefore, will have had a prior dengue infection before vaccination.”

Dengvaxia, the first approved Dengue vaccine, had been forecast by Sanofi to eventually bring in nearly $1 billion in annual sales. But even recent more modest analysts’ sales forecasts are now looking unattainable given the safety issue and clinical evidence revealing unequal protection against different strains of dengue.