Developing a Vaccine
Despite decades of effort by many scientists to develop a vaccine for dengue, no licensed vaccine is available. The problem begins with the virus itself (or really, the viruses). Dengue is caused by infection with any of four closely related dengue viruses, and a successful dengue vaccine must offer immunity against all four. Infection with one type of the virus produces life-long immunity but only to that one dengue virus. Infection with another dengue virus increases the chance of developing dengue hemorrhagic fever or dengue shock syndrome, both serious and potentially deadly diseases. Typically, an epidemic caused by one dengue type is followed a few years later by an epidemic caused by one of the other three. In most dengue-endemic countries, most teenagers have already been exposed to multiple dengue viruses.
Dr. Claire Huang and her team in the Division of Vector-Borne Diseases (DVBD) at Fort Collins, CO, have developed a dengue vaccine candidate that is now being clinically evaluated in the United States and Colombia for safety and efficacy. The first human Phase-I trial showed that the vaccine was safe, well tolerated, and produced antibody levels that should protect against all four dengue viruses. Because of these encouraging results, a Phase-II clinical trial to assess immunogenicity (ability to provoke an adequate immune response) will begin in 2012. A successful Phase-II trial would be followed by Phase-IIb or Phase-III trials to determine efficacy at a much larger scale. Clearly, development and testing of a human vaccine requires many steps.
This technology has been awarded multiple U.S. and international patents. CDC’s dengue vaccine team has partnered with Inviragen, Inc., a Colorado-based vaccine manufacturer. Inviragen is manufacturing the vaccine, named DENVax, and is conducting clinical development and testing of the vaccine for human use. The goal is to provide a safe, effective, and affordable dengue vaccine to protect billions of people living in or traveling to dengue-endemic countries.