WHO approves first-ever dengue vaccine
The painful and sometimes deadly mosquito-borne disease is on the
rise, but a new vaccine could help the most vulnerable populations
Dengue vaccine: US develops new completely
effective vaccine - msg.com
The World Health Organization (WHO) on Friday endorsed the world's
first-ever vaccine for dengue fever, a potentially deadly mosquito-borne
virus that threatens to infect close to half of the world's population.
Unlike malaria, there is no established cure for dengue fever, which
can cause severe nausea, bone pain, headaches, rashes, bleeding and even
death. The virus can last for up to 10 days. About 390 million people
are infected by dengue each year in some 120 countries, particularly in
Southeast Asia, Latin America and Africa.
Known as Dengvaxia, the vaccine is the product of two decades of
research by French-based Sanofi Pasteur. Four countries-Mexico, Brazil,
El Salvador and the Philippines-have already licensed Dengvaxia, but
Friday's recommendation is likely to spur a host of other developing
nations to follow, at a time when climate change and urbanisation is
putting increasing numbers of people at risk from the mosquito-borne
disease. "In countries where dengue is endemic, it's one of the most
feared diseases," says Dr. In-Kyu Yoon, director of the Dengue Vaccine
Initiative, an international consortium that has partnered with Sanofi.
"The trajectory globally is increasing-at this point it's essentially a
The vaccine is given in three injections, spaced out over one year.
It is designed for those over the age of nine who have been previously
exposed to the virus and is best suited for people in endemic areas, as
opposed to short-term travellers, according to Dr. Alain Bouckanooge,
Associate Vice President of clinical research and development at
Sanofi's division in Thailand.
Throughout the past few years the company conducted clinical trials
in tens of thousands of children in Southeast Asia and Latin America
that revealed the vaccine to be 70 percent effective for those with
pre-exposure to dengue and 90-95 percent effective against severe
Scientists have been unable to develop a vaccine for dengue in part
because the virus is so complicated. It has four strains, more than
other deadly diseases such as polio and smallpox. If a person gets
infected with more than one type of dengue, there is a greater chance of
the virus of causing hospitalisation or death. Yoon said there have
historically only been a few places where more than one serotype of
dengue circulates at any given time, but urbanisation has made it more
common to have multiple serotypes in the same area.
Another challenge in testing the vaccine has been the need for
expensive and time-consuming human trials. Bouckanooge says there is no
good animal model that can be used as a predictor. "For the dengue
vaccine you don't have that. Human dengue is quite unique," he said.
Even a successful vaccine won't eliminate dengue overnight. Sanofi's
production capacity is limited, Yoon said. He estimates that the company
could manufacture about 100 million doses of the vaccine annually,
compared to an estimated demand of about one billion doses over five
years. "So there are potentially some supply and demand issues," he
said. "Clearly there is a need for more than one vaccine and more than
one vaccine manufacturer," he said.
Dengvaxia's side effects include systemic headaches, fatigue and
light-grade fevers. No direct fatalities have been reported.
The decision whether or not to introduce the vaccine will be up to
individual governments. While the WHO does offer information resources
to aid countries, setting up a vaccination program will provide its own
set of challenges, according to Joachim Hombach, senior advisor in WHO's
Initiative for Vaccine Research.
"You need to buy the vaccine and it costs a lot money," he said. "And
you are in the business for many years - it's essentially an open-ended
commitment. You don't want to be in a situation where you introduce a
vaccine and then two years later you say, oops, sorry, we are running
out of money and we have to stop this program," he said.