WASHINGTON, DC—With two-fifths of the world’s population at risk for dengue fever, a severe flu-like illness which sometimes leads to fatal complications, the development of a vaccine has long been an important, albeit elusive, goal in managing the disease.
Now, public health experts are expressing optimism about the development of a dengue fever vaccine in the near future.
“We have some very exciting leads on different types of vaccines that are in various stages of clinical trials that, hopefully, can be implemented within a reasonable period of time,” NIH Director. Anthony Fauci, MD, said at a recent conference.
As many as 100 million people are infected yearly with mosquito-borne dengue infection, according to the CDC in Atlanta. No vaccine currently exists to prevent dengue infections nor effective drug treatment for those who contract it, experts said.
Fauci and other scientists recently gathered for a three-day scientific meeting held in Puerto Rico to discuss the latest dengue research, identify research gaps and priorities, and promote future research collaborations among government agencies, research institutions and universities. The conference was co-hosted by National Institute of Allergy and Infectious Diseases (NIAID), CDC and the Pan American Health Organization (PAHO).
Several dengue vaccine candidates are in different stages of development, including an advanced vaccine candidate by Sanofi-Pasteur that entered its first Phase III clinical study in Australia in late 2010. Fauci said that if the trials for that vaccine candidate prove successful, a vaccine might only be a few years away.
“When you talk about the vaccines that are in different stages, from concept to preclinical to phase 1, it is virtually unpredictable when we’re going to get it,” said Fauci. “But if the ones that are advanced in phase III are in fact successful, you’re talking a few years—three, four, five years away—maybe even earlier, depending on the results.”
Dengue in U.S.
While dengue has been in the Americas for several centuries, Fauci said that most people do not appreciate that dengue continues to play a major role in disease, particularly in areas such as Latin America, and to some extent in other developing, middle, and low-income countries in Africa and Asia.
Puerto Rico experienced the largest dengue fever outbreak in its history in 2010, recording more than 21,000 cases. As for the continental United States, in Key West alone, there were 69 cases of clinical dengue last year. In addition, CDC said it receives about 500 reports a year of US travelers who get infected, calling that a likely “underestimate.”
Fauci said that NIH’s commitment to dengue research has increased over the past several years, despite a “relatively flat budget” at NIAID and at NIH in general. For FY 2010, NIAID devoted $45 million on dengue research, which is up from $30 million in 2005 and $5 million in 2000. Basic research comprised 62% of that funding, while vaccine funding made up 24% of the budget and therapeutics and diagnostics made up the rest. NIAID funds nearly 60 dengue research projects, including studies on dengue hemorrhagic fever and dengue shock syndrome, the most severe complications of the disease.
For the last 30 years CDC has had a lab in Puerto Rico working on dengue epidemiology, diagnostics and vector ecology and control issues. CDC also has been training physicians in Puerto Rico on World Health Organization guidelines for the clinical management of dengue fever in collaboration with the Puerto Rico Department of Health, the College of Physicians-Surgeons of Puerto Rico, PAHO, Puerto Rico Academy of Family Physicians, Puerto Rico Pediatric Society, and the Medical Association of Puerto Rico.
Dengue Vaccine Would Reduce Fever’s Threat to Deployed Military Troops
Since troops can be vulnerable to dengue fever infection when they deploy, military scientists are among the researchers working on the development of a vaccine for the sometimes serious, flu-like disease, Lt. Cmdr. Tad Kochel told U.S. Medicine.
Kochel is the chief of the Naval Medical Research Center’s Viral and Rickettsial Diseases Department, which is working on the advancement of a dengue vaccine.
Without a vaccine or effective treatment, dengue infection poses a threat to troops because it has the potential for “knocking down large groups of personnel at one time,” he said. “If you have a significant number of your personnel flat on their backs for two weeks, it completely stops operations.”
Currently, Kochel said that there are three main dengue vaccine candidates under development at the Naval Medical Research Center. Though none of them on their own are adequate, researchers are now examining them in combination with one another. “The idea there, and we have seen this with other pathogens, is that the individual components are not good enough for whatever reason by themselves,” he said. “But when you follow one with another you get acceptable types of protection. We are going into clinical trials this summer with that prime boost approach.”
In general, a challenge in dengue vaccine development is the disease’s four serotypes, meaning that a vaccine must really consist of “four vaccines,” Kochel explained. An individual who becomes infected with one serotype will develop protection from subsequent infection of that same serotype. If that individual is then later on infected with another serotype, however, they will be at risk for more severe disease.
“So in the vaccine world what we have do is to make sure we are not setting up that type of situation with our vaccine …, The vaccine must be protective against all four serotypes,” he said.
With troops that must deploy in a timely fashion, the military also requires a vaccine in which the dosing intervals are not too far apart. “What we are trying to look at with our prime boost study, is can we shorten the interval between doses? Can we come up with a product that is 100% protective that maybe the immunization can be done within a month,” said Kochel.
With the efforts to develop a dengue vaccine both inside and outside of the military, Kochel added that he is “very optimistic” that a vaccine suitable for troops will be available “within the five to 10 year time frame.”