LONDON/PARIS, (Reuters) – The world’s first vaccine against dengue fever, being developed by French drugmaker Sanofi SA, protected against three of the virus’s four strains in a keenly awaited clinical trial in Thailand.
Sanofi said yesterday the proof of efficacy was a key milestone in the 70-year quest to develop a viable dengue shot, adding the results also confirmed the safety profile of its vaccine candidate, which could reach the market in 2015.
Other drug companies are also working on dengue vaccines but Sanofi’s product is several years ahead.
The mosquito-borne disease, also known as “breakbone fever”, is a threat to nearly 3 billion people and is caused by four different types of virus, none of which confers immunity from the others.
Sanofi’s vaccine generated an antibody response for all four dengue virus types, but evidence of protection was only demonstrated against three of the four strains circulating in Thailand.
Duane Gubler of the Duke-N.U.S. Graduate Medical School, who has researched dengue for four decades, said the results looked “great”, despite the failure to defend against all strains.
“I am not at all concerned about the lack of protection against all four serotypes. Based on what we know about the immune response to dengue viruses, if the vaccine protects against three serotypes, recipients will be protected against severe disease,” he said in an emailed exchange.
Sanofi said researchers were carrying out analyses to understand the lack of protection for the fourth serotype.
“It’s a surprise,” company spokesman Pascal Barollier said. “We need to get to the bottom of the data to find out why it is reacting this way and wait for ongoing Phase III trials to see if it is linked to some specific situation in Thailand.”
The Phase IIb study involving 4,002 Thai children aged four to 11 years was conducted during a dengue epidemic, which might be an explanation for the unexpected outcome.
