Results from a new study run by researchers at the University of Vermont and Johns Hopkins University show big strides in the development of a vaccine for the dengue virus. To learn more about this study released March 16, VPR's Mitch Wertlieb and Kathleen Masterson spoke with the research team at UVM on Friday.
The dengue virus is the most common mosquito-borne viral infection in the world, infecting nearly 400 million people annually. At its most severe, the flu-like disease can be fatal.
The study tested a vaccine developed by the National Institutes of Health. It marks the first time this type of early-stage efficacy test on humans has been conducted for a dengue vaccine, and shows it to be completely effective at protecting humans from a weakened form of the virus.
The results are so promising researchers say they could speed up development of the vaccine.
“It gives us an early indication that vaccine will be successful, and this information would be otherwise much longer in coming,” says Beth Kirkpatrick, a professor of infectious disease medicine at UVM, who led the vaccine study.
“It would have to be done through a lengthy field trial in disease-endemic areas, which would take three to 10 years — and probably tens of millions of dollars," Kirkpatrick says.
There’s currently no vaccine against the dengue virus that’s commercially available worldwide, but a French vaccine has been approved for use in three countries.
The NIH vaccine will still have to be tested in large-scale clinical trials to be approved for commercial use — work that has already begun at research partner organization, the Butanan Institute in Brazil.
The researchers say this early success helped inform the Butanan Institute which vaccine formulation to take into their phase three trial, which is the next step to confirming the vaccine’s efficacy. Previous dengue vaccines have tested well in animals only to fail to prove protective in people.
"It gives us an early indication that vaccine will be successful, and this information would be otherwise much longer in coming." - Beth Kirkpatrick, UVM professor of infectious disease medicine
Another challenge is that there are four strains of virus which cause dengue. The vaccine tested at UVM is designed to protect against all four forms of the virus. The vaccine is called TV003, and it’s a live attenuated vaccine, which means pieces of the real dengue virus are used to help the body create antibodies.
This recent study tested the vaccine’s ability to prevent infection from Dengue 2, though UVM researchers are currently testing the same vaccine against Dengue 3.
Testing on humans
The test works by taking a small group of volunteers (48, in this case), and giving half the dengue vaccine and half a placebo. Six months later, all the volunteers are infected with a completely safe mild version of the dengue virus.
Kirkpatrick says the results were “very straightforward and conclusive, all the volunteers who received the vaccine six months earlier were protected from infection with the weakened Dengue 2 strain, with no evidence of circulating virus, no rash, and no change in white blood cells.”
Researchers say this model will not only help evaluate if the vaccine works, but also helps scientists understand the body's immune response to dengue.
In contrast, she notes that every one of the placebo volunteers had evidence of the virus in circulating in their bloodstream, 80 percent developed a rash and 20 percent had a drop in white blood cells.
The testing is randomized and double-blind, so neither the volunteers nor the vaccine administrators know who is getting the real vaccine and who is getting the placebo.
Hope for a Zika vaccine?
Researchers say this model of testing can also help scientists understand the body’s immune response to dengue.
“We’re using this model not just to test the vaccine’s efficacy, but also to interrogate the body’s immune response to dengue with ultimate goal of determining … how much antibody is needed for protection? What other types immunity are important? How quickly does it begin to take effect after vaccination? How long does immunity last?” says Anna Durbin, a professor at Johns Hopkins Bloomberg School of Public Health working with the UVM and NIH researchers.
That’s important not only for Dengue, but also for a related virus: Zika.
Scientists hope to use the same early-stage model of testing to help them study the Zika virus.
“There’s real potential to better understand Zika itself, we know so little about it right now,” says Durbin. “How long it stays in the blood, how long it can be excreted in urine or semen.”
The University of Vermont Vaccine Testing Center has been selected to help test a potential vaccine that the NIH is developing against the Zika virus. The center says it hopes the Zika vaccine will be ready to test by this fall.
* This story was originally posted on March 16, 2016. Since then we conducted additional interviews with UVM, Johns Hopkins University and National Institutes of Health researchers, and this story has been updated with that audio.
