Roughly 4,000 children between the ages of 4 and 11 years old received three doses of the vaccine, given in six-month intervals. An immune response was observed against four serotypes of the dengue virus after three doses, and showed minimal adverse effects following each dose.
“Results of this first efficacy trial with Sanofi Pasteur’s dengue vaccine candidate represent a key milestone in the quest to develop a safe and efficacious human vaccine against dengue,” said Michel De Wilde, executive vice president of research and development at Sanofi Pasteur.
While the vaccine candidate produced an immune response to fight the four types of the dengue virus, researchers say that sufficient protection was only offered against three. As the vaccine candidate moves onto further trials, the company stated that it will conduct further analyses to understand the lack of protection against the fourth subtype in the context of Thailand.
The full results of the study are currently under review by scientific experts and health officials, and details of the study will be published and presented to the scientific community later this year.
The vaccine candidate is a live attenuated vaccine, meaning that it uses a weakened version of the causative agent, which is in this case the dengue virus, to stimulate an immune response. The dengue vaccine contains four antigens to target all four serotypes of the virus.
Live attenuated vaccines are used to protect against a variety of diseases, such as measles, polio and yellow fever. They are considered to be the most effective type of vaccine. With only one or two doses, they can elicit lifelong immunity.
Other types of vaccines use dead versions of a pathogen (modern flu vaccines) or subunits (pieces) of a pathogen (HPV vaccine) to stimulate a response. But those often require a larger dose or a booster to provide protection.
Opting for the live attenuated vaccine has its challenges. For starters, it is a live organism, and therefore has to be kept alive. Areas without electricity or a method to keep the vaccine chilled prior to distribution are at a disadvantage.
Sanofi Pasteur stated that the Food and Drug Administration has given a “fast-track” designation to the company’s research of the vaccine candidate, in order to “address an important unmet medical need for a serious disease.”
Currently, there is no cure and no effective treatment for dengue. Recent efforts have focused on control and elimination of the Aedes aegypti mosquito, the insect responsible for passing the virus between humans. An effective vaccine could help protect the nearly three billion people at risk for dengue infection and save 20,000 lives each year.
Researchers are currently conducting a larger study of over 30,000 participants in 10 countries in Latin America and Asia. The data collected there will provide more information about how the vaccine fairs against the four subtypes in a variety of settings.