Sanofi is warning that their new vaccine against dengue fever should only be given to people who have already been infected with the dengue virus due to safety concerns.
For people who have never had dengue, vaccination with Dengvaxia can lead to a more severe disease, according to Sanofi’s analysis of 6 years of data.
That means everyone who was vaccinated proactively is now at risk of getting the most severe form of the disease for the rest of their lives.
Dengvaxia is sold in dozens of countries, from Thailand to Brazil. It is currently recommended in dengue-endemic countries for people over 9 years old.
Sanofi is updating the guidelines to recommend the vaccine only for people who have had dengue before:
“For those not previously infected by dengue virus…the analysis found that in the longer term, more cases of severe disease could occur following vaccination. These findings highlight the complex nature of dengue infection.”
The World Health Organization (WHO) estimates that 96 million people are infected with dengue every year. Dengue is caused by a mosquito-borne virus in tropical and subtropical parts of the world.
The infection causes a flu-like illness, with fever, headache, joint pain, and a rash. Dengue occasionally develops into a potentially deadly hemorrhagic version of the disease, with severe breathing problems, bleeding, and organ failure.