JHSPH Researchers Announce Vaccine Against Disease That Infects 400 Million Every Year
The existence of four varieties of dengue have made developing an effective vaccine vexingly difficult. To be fully protective, a dengue vaccine has to protect against all four strains and protection must last—two issues that have presented major challenges in the search for a dengue vaccine.
Further, infection with one strain doesn’t grant long-term immunity from the others and contracting a different strain later can cause a more serious case of the disease which infects nearly 400 million people across more than 120 countries each year. Most show few or no symptoms, but of the two million people who develop dengue hemorrhagic fever annually, 25,000 don’t survive.
In March 2016, an exciting dengue vaccine breakthrough emerged from a small clinical trial led by Bloomberg School International Health professor Anna P. Durbin, MD, who has been working to develop a dengue vaccine for more than 15 years.
Calling the results “incredible” and a “tremendous step forward,” leading virologists said that the research is the first major advance in decades in the fight against dengue.
The development of a dengue vaccine has had a stop-and-start history. In one promising trial in Brazil, for example, a three-dose vaccine that had produced antibodies conferred protection for a year, but the vaccine failed to protect against dengue two years post-vaccination.
When Durbin’s team was designing a clinical trial to test the NIH-developed single-dose vaccine, known as TV003, a primary concern was that measuring antibodies alone may not be a reliable indicator of the vaccine’s ability to protect against dengue. So to be certain of a vaccine's protective abilities, the researchers decided to look for evidnce of the virus in the blood as well. TV003 had shown good results in preventing dengue 1, 3 and 4 viruses, but the immune response against the 2 virus was not as strong.
For the investigation, researchers from the Bloomberg School and the University of Vermont gave the vaccine to 24 adults, while 24 got a placebo. After the 41 remaining participants who were vaccinated were exposed to dengue 2 virus six months later, their blood test results showed no evidence of infection, while all of the placebo recipients were found to be infected.
"Dengue is unique and if you don’t do it right, you can do more harm than good."
“Knowing what we know about this new vaccine, we are confident that it is going to work,” Durbin says. “And we have to be confident: Dengue is unique and if you don’t do it right, you can do more harm than good.”