The World Health Organization will conduct a review of pharmaceutical giant Sanofi's dengue vaccine by year-end after evidence surfaced suggesting the vaccine could worsen the disease in some cases, according to Reuters.
The clinical trial data, disclosed by the French drugmaker, suggests the vaccine may increase the risk of infection and worsen the symptoms of dengue in the long-term for people who were not exposed to the virus prior to vaccination.
"The analysis confirmed that Dengvaxia [the vaccine] provides persistent benefit against dengue fever in those who had prior infection," said Sanofi in a statement. "For those not previously infected by dengue virus, however, the analysis found that in the longer term, more cases of severe disease could occur following vaccination upon a subsequent dengue infection."
Dengvaxia has been approved in 19 countries, though a large majority of its sales have come from the Philippines through its government immunization program, which involved vaccinating more than 730,000 children, according to Reuters. On Monday the Filipino government ordered a probe into the immunization of these children. Pending review of the probe, the Philippines FDA ordered Sanofi to pull the vaccine off the market.