A health worker prepares to administer a vial of dengue vaccine in the Paraná state of Brazil in 2016.

Sanofi Pasteur/Gabriel Lehto/Novas Imagens Cine Video/Flickr (CC BY-NC-ND 2.0)

If you haven’t had dengue infection, don’t use our vaccine, drug company warns

The manufacturer of the sole dengue vaccine on the market says a new study shows that it should only be used in people who have had a previous infection from the mosquito-borne virus.

As Reuters and several other news outlets have reported, France’s Sanofi Pasteur released a statement that said a 6-year analysis of people who received the vaccine found more severe disease occurred in people who initially were naïve to the virus. Sanofi Pasteur stressed that the vaccine still protected against dengue fever when it was given to people who had prior dengue infections.

The company did not spell out the mechanism underlying the responses to the vaccine. But several researchers have warned that the vaccine could trigger antibodies in a naïve subject that enhance the ability of a second infection to cause severe disease, including a deadly hemorrhagic fever.