Scientists are applauding the results of a dengue vaccine experiment. They are saying the new treatment may finally stem the disease and be a framework for a future vaccine for the Zika virus.
The experiment involved 48 participants who volunteered to be infected with the mosquito-borne dengue fever virus.
In all, 100 percent of the participants who received the vaccine were protected from the disease. All of the volunteers who received a placebo came down with mild symptoms of the illness.
“The findings from this trial are very encouraging to those of us who have spent many years working on vaccine candidates to protect against dengue, a disease that is a significant burden in much of the world,” Stephen Whitehead, Ph.D., of NIH’s National Institute of Allergy and Infectious Diseases (NIAID), said in a statement.
How the Experiment Worked
The trial began with 48 volunteers at two trial sites, the University of Vermont College of Medicine and the Johns Hopkins Bloomberg School of Public Health.
Half of the participants received one shot of the experimental vaccine and the other half received a single treatment involving a placebo.
Six months later, 41 of the original volunteers returned. All of them were then infected with a genetically modified version of the dengue-2 serotype virus, a strain of the disease that usually produces only mild symptoms.
None of the 21 volunteers who received the vaccine, known as TV003, developed the illness. All of the 20 participants who were given the placebo developed either a rash or a temporary decrease in white blood cell count.
“We were pleasantly surprised to see that this candidate vaccine provided complete protection in everyone who received it,” Dr. Anna Durbin, who oversaw the Johns Hopkins trial, said in a statement.
Nearly 400 million people are infected every year with the dengue virus. The illness is particularly common in Puerto Rico and in tourist destinations in Latin America, Southeast Asia, and the Pacific islands, according to the U.S. Centers for Disease Control and Prevention (CDC).
Most people who are infected develop either mild or no symptoms. However, 2 million develop the most serious form of the virus, and 25,000 die from it every year.
The Challenges of Dengue
There are actually four strains, or serotypes, of the dengue fever virus.
This has made it difficult in the past to develop a vaccine that is effective against all four strains, according to a story in The Washington Post.
In addition, there has been a concern that if a vaccine doesn’t protect against all four serotypes, it can actually put a patient at risk of developing a more severe form of one of the strains.
This TV003 vaccine consisted of a mixture of four live weakened viruses targeted at each of the serotypes.
Whitehead told The Post the proliferation of dengue around the world justified using human volunteers in the study.
He said the results of this experiment were so promising that a large-scale phase III test began in Brazil on Feb. 22. That trial is expected to involve 17,000 adults and children and last until 2018.
Moving on to Zika
Dengue fever and Zika are from the same family of viruses, and the same breed of mosquito carries both.
The success of the dengue vaccine experiment bodes well for development of a Zika vaccine, scientists told The Post.
NIH officials said they should be able to reduce the timeline for a Zika vaccine if they build on the work from the dengue experiment.
They said some small experiments involving human volunteers and potential Zika vaccines could be ready as early as this summer.
Dr. Lee Norman, the chief medical officer at the University of Kansas Hospital, told Healthline he’s optimistic researchers could make the jump from the dengue to the Zika vaccine.
“The viruses are closely related, even in the same family, and as such the learned lessons from dengue may help shorten the development cycle for discovering a Zika vaccine,” Norman said in an email. “And the antibody tests that currently show whether or not a patient has had Zika and/or dengue cross-react, suggesting that the natural antibodies a person makes are similar in the antigen they seek to attack.”
Zika Outbreak Spreads
The most common symptoms of Zika infection are fever, rash, and joint pain. Most people suffer mild symptoms for a few days to a week, according to the CDC website.
However, the Zika virus has been linked to a serious birth defect called microcephaly in babies whose mothers were infected during pregnancy, according to the CDC.
The latest Zika outbreak began two years ago in Brazil. According to the latest figures from the World Health Organization (WHO), the disease has been documented in 33 countries since 2014.
The latest countries to report Zika presence are Cuba and Dominica.
The WHO report also states 12 countries or territories have reported increased cases of Guillain-Barre syndrome (GBS) and/or laboratory confirmation of Zika virus infection among GBS patients.
Norman said the extent of the Zika outbreak really isn’t known at this point.
There are not enough community and public health workers in those regions to really know the accurate numbers,” Norman said. “Plus, it will be very important to know how many strains of Zika there are and whether a person can get it more than once, like dengue.”