First Vaccine for Dengue Fever Shows Promise in 2nd Big Trial
An experimental vaccine against dengue fever being developed by Sanofi proved about 60 percent effective in its second large clinical trial. The results could clear the way for the introduction of the world’s first inoculation against the disease, which is mosquito-borne and becoming an increasing threat.
Sanofi, a French drug company, said on Wednesday that use of the vaccine cut the risk of getting dengue by 60.8 percent in the trial, which involved 20,875 children ages 9 to 16 from several countries in Latin America and the Caribbean.
Those who received the vaccine also had an 80.3 percent lower risk of being hospitalized for dengue compared with children who received injections of a placebo.
The results are roughly similar to those from the first large clinical trial, in which the vaccine reduced the incidence of dengue fever by 56.5 percent. That trial involved about 10,000 children in Southeast Asia.
“For the first time ever, after 20 years of research and industrial commitment, dengue is set to become a vaccine-preventable disease,” Olivier Charmeil, chief executive of Sanofi Pasteur, the vaccine division of Sanofi, said in a statement.
A question now is how widely such a vaccine would be adopted. Some experts hoped for a greater effectiveness, especially since in the first large trial, the vaccine was somewhat less effective in younger children, who are most vulnerable to the disease. Both trials were late-stage versions known as Phase 3.
“It’s certainly not anywhere close to what we had hoped, something that would reach up into the 90s,” said Dr. Scott B. Halstead, scientific adviser to the nonprofit Dengue Vaccine Initiative.
Still, he said, the vaccine does appear to prevent severe disease. Moreover, Sanofi is a few years ahead of others in developing a vaccine. Those factors could persuade countries to use the product.
Sanofi executives argue that with no other vaccine and no treatments available for dengue, a vaccine that reduces the number of cases by more than half and hospitalizations by 80 percent represents a big advance.
“When I talk to health ministers, they’re pretty excited about this, actually,” Christopher A. Viehbacher, Sanofi’s chief executive, told analysts in a conference call discussing quarterly earnings in late July.
Mr. Viehbacher said the company would apply for approvals in the first quarter of 2015 and hoped to begin sales in the fourth quarter of that year. He said the priority countries would be Mexico, Brazil and Colombia and possibly Singapore and Malaysia.
The company plans to apply eventually for approval in the United States as well, executives said.
Sanofi has invested more than 1.3 billion euros, or $1.7 billion, in developing the vaccine. Guillaume Leroy, dengue vaccine chief at Sanofi Pasteur, said the company had already begun manufacturing vaccine in a new factory it built outside Lyon so as to have enough ready by 2015. He said that beginning in 2016, the company would have the capacity to make 100 million doses a year.
An estimated 50 million to 100 million people a year are sickened by dengue, though that might be an underestimate. The disease, also known as breakbone fever, can cause high temperatures and intense joint and muscle pain.
In the most severe cases, infection causes hemorrhagic fever, which is characterized by bleeding and shock and can be fatal. The number of dengue cases has been increasing rapidly worldwide in part because of urbanization, since the mosquito that carries the disease is well adapted to urban areas. Dengue is even moving out of tropical areas in developing countries to industrialized countries in more temperate zones.
There is now an outbreak in Tokyo, the first one in Japan in nearly 70 years. Yoyogi Park is being fumigated to try to eliminate disease-carrying mosquitoes. The Florida Keys had its first cases in decades in 2009.
Sanofi said that in the second trial, as in the first, the vaccine was more effective in people previously exposed to dengue. That might make the vaccine especially useful in endemic areas, where people often are exposed more than once, but it would probably make it less useful for tourists traveling to an infected area.
The vaccine is a live weakened yellow fever virus that is genetically engineered to make proteins from the four subtypes of dengue virus. It is given as three shots spaced over a year.
The vaccine seems particularly weak against one of the four subtypes of dengue, known as Serotype 2. In the Latin America trial, the protection against that serotype was only 42.3 percent, compared with 50.3 percent protection against Serotype 1, and greater than 70 percent protection against Serotypes 3 and 4.
Sanofi said the vaccine seemed safe in the new trial, as it had in the previous trial, with the rate of so-called adverse events being the same in the vaccine arm and the control arm.
Sanofi announced the results in a news release, saying more detail would be presented at a medical conference in November and published in a journal. The trial took place in Brazil, Colombia, Honduras, Mexico and Puerto Rico.
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