Early analysis from the world's first ever efficacy trial of an
experimental vaccine against dengue fever shows promising results. In a study
involving 4,000 children in Thailand, the vaccine appeared to prevent infection
by three of the four circulating strains of the virus and showed an excellent
safety profile, its French drug maker Sanofi told the press on Wednesday.
The purpose of Sanofi's dengue
vaccine is to prevent dengue disease in children and adults living in endemic
areas of Asia and Latin America, and also for children and adults travelling to
endemic countries, such as expatriates, military personnel, and their families.
Michel De Wilde, Executive Vice
President of Research and Development at Sanofi Pasteur, the vaccines division
of Sanofi, said the results of the trial "represent a key milestone in the
quest to develop a safe and efficacious human vaccine against dengue".
"This is also an important
development for global public health, since there is currently no specific
treatment or prevention for dengue," he added.
Dengue Disease
The rate of dengue, a
mosquito-borne infection found in tropical and sub-tropical regions, has risen
dramatically around the world in recent decades, mostly in urban and semi-urban
areas. It is also spreading geographically: a recent outbreak in Florida shows
that dengue is now reaching continental USA outside the endemic areas of Hawaii
and Puerto Rico.
There are currently 50 to 100
million people infected every year, and over 40% of the world's population,
that is over 2.5 billion people, are estimated to be at risk, says the World
Health Organization (WHO).
There are four related but
distinct viruses that cause dengue fever. The infection causes flu-like
symptoms, and occasionally develops into hemorrhage and shock, known as severe
dengue, a leading cause of serious illness and death among children in some Asian
and Latin American countries.
There is currently no effective
treatment for dengue fever, and the only way to control its spread at present
is to control the mosquito.
The US Food and Drug
Administration (FDA) has given Sanofi's experimental dengue vaccine fast track
status, meaning the federal agency recognizes such a vaccine potentially meets
an important unmet need for a serious disease.
The Thailand Trial
The Sanofi Pasteur dengue vaccine
candidate is a live attenuated vaccine, given as 3 doses, 6 months apart (month
0, month 6, and month 12 of the trial).
The safety and efficacy trial was
conducted in 4,002 children aged 4 to 11 years in Thailand, as a partnership
between Sanofi Pasteur and the Mahidol University under the patronage of the Thai
Ministry of Public Health in Muang district of the Ratchaburi Province.
Sanofi say the vaccine generated
antibody response for all four dengue virus serotypes and early analysis of the
trial results show evidence of protection against three of the four virus
serotypes circulating in Thailand.
The company say they are still
analysing the results to understand why the vaccine failed to protect against
the fourth virus serotype "in the particular epidemiological context of
Thailand".
The most important news, they
say, is the results confirm the "excellent safety profile" of the
experimental vaccine.
The full data is now being
reviewed by experts and public health officials, and the intention is to
publish the results of the study in a peer-reviewed journal for scrutiny by the
scientific community later this year.
Large scale phase III trials of
the dengue vaccine are already under way. These involve 31,000 participants in
10 countries, 5 in Asia (the Philippines, Vietnam, Malaysia, Indonesia, and
Thailand) and 5 in Latin America (Mexico, Colombia, Honduras, Puerto Rico and
Brazil).
The studies are expected to
generate important extra data about how the vaccine performs against the four
circulating dengue viruses in a wider population in varied settings.
Catharine Paddock PhD
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