In a year in which dengue has almost quadrupled in Cambodia, the world’s first vaccine against dengue has shown the ability to protect against disease caused by three of four virus strains, in a keenly awaited clinical trial in Thailand.
The developer, French drugmaker Sanofi SA, 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 the vaccine candidate.
Dengue is endemic in Southeast Asia and, like Cambodia, countries worldwide have had very little success in controlling it, World Health Organization Cambodia epidemiologist Steve Bjorge told the Post.
“The only control is larvicide and sanitation of the environment,” Bjorge said, pointing out that as yet there was no cure for the disease. “An effective vaccine would be a real help.”
Cambodia dengue numbers in the first half of the year compared to those in 2011 have almost quadrupled, with 15,600 cases reported compared to 4,604 for the same time last year. The death toll is now at 60, and a premature rainy season caught health officials off guard.
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.
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.
Deutsche Bank analyst Mark Clark said the lack of protection against the fourth virus type meant a commercial launch was more likely in 2015 than in 2014, as Sanofi awaits Phase III data rather than filing early in some countries.
“More positively, given that protection against at least three of the four viral types has been demonstrated, the data supports the likelihood of launch for this huge unmet clinical need,” Clark wrote in a research note.
The company’s vaccine unit Sanofi Pasteur has already invested 350 million euros ($423 million) in a new French factory to make the three-dose vaccine and believes its product could generate more than 1 billion euros in yearly sales.
But uptake of the vaccine will depend on precisely how well doctors believe it can protect populations at risk in fast-expanding tropical cities from Rio to Manila, as well as travellers to such areas.
Sanofi, which reports second-quarter results today, gave no details on the level of protection in a brief statement. The full data are now being reviewed by scientific experts and public health officials, with detailed results to be published later this year.
Large-scale late-stage Phase III clinical studies with 31,000 participants are under way with Sanofi’s vaccine in 10 countries in Asia and Latin America.
With assistance from Bridget Di Certo