With Florida health officials reporting more mosquito-borne Zika infections in Miami-Dade, including one new case confirmed Monday, scientists with the Walter Reed Army Institute of Research (WRAIR) launched the first of five early stage clinical trials that they hope will lead to the development of a vaccine against the virus.
A Zika vaccine is still two to three years away from public availability, according to scientists, but most vaccines have traditionally taken a decade or longer to develop.The shorter time frame is due in part to lessons learned from prior infectious disease outbreaks.
Kayvon Modjarrad, a physician researcher and associate director for emerging infectious disease threats at WRAIR, said scientists developed the trial vaccine, called Zika purified inactivated virus, or ZPIV, using the same technology they used to create a Japanese encephalitis vaccine licensed in 2009.
“It’s based on a technology that has been around for a long time,” he said.
There are currently three Zika vaccine candidates undergoing human clinical trials, but ZPIV is the only one that uses a weakened or dead virus to provoke an immune system defense.
The other two candidates are DNA vaccines that also elicit immune system response by using genetically engineered DNA that stimulate cells. They are being tested separately in clinical trials by the National Institutes of Allergy and Infections Diseases and by Inovio Pharmaceuticals — though no DNA vaccine has ever been licensed for human use.
After preclinical studies in early July showed that two doses of ZPIV, administered four weeks apart, provoked a protective immune response to Zika in rhesus monkeys, the vaccine candidate advanced to human trials.
1,133 Zika infections reported in Florida this year
Currently, there are five different clinical trials scheduled using ZPIV, Modjarrad said, including one by St. Louis University researchers to determine the optimal dose of vaccine to be used in larger studies.
Other ZPIV studies will evaluate the safety and effectiveness of administering the vaccine candidate in a shortened time period, and its ability to prevent Zika in people who have been naturally exposed to Zika or dengue. A fifth trial will examine the effectiveness of using the DNA and ZPIV vaccine candidates together.
For the ZPIV human clinical trial launched Monday, WRAIR scientists will recruit 75 healthy adult volunteers who have never been infected with any of a related group of viruses, including yellow fever, dengue, West Nile, Japanese encephalitis and Zika.
Because military personnel are deployed on short notice to places where infectious diseases are endemic — and because Army scientists want to understand how a Zika vaccine would react when used with other vaccines — the ZPIV clinical trial launched Monday will include groups that are also being vaccinated against Japanese encephalitis and yellow fever.
Modjarrad said a Zika vaccine using ZPIV may be ready for commercial use in two to three years, echoing a time frame cited by Centers for Disease Control and Prevention Director Tom Frieden during a speech in Miami in October.
With Zika we got lucky because we had a lot of experience, research and data ... that we could then use and translate over into Zika.
Dr. Kayvon Modjarrad of Walter Reed Army Institute of Research
But two years is an improvement over the traditional decade-long time frame for developing vaccines, Modjarrad said, noting that scientists have benefited from increased investments in laboratory and other technologies and streamlined regulations since Ebola was reported in the United States in 2014.
“With Zika we got lucky,” he said, “because we had a lot of experience, research and data from dengue and yellow fever and Japanese encephalitis that we could then use and translate over into Zika.”
If the early phase of the clinical trial for ZPIV is safe and effective in human volunteers, then the vaccine candidate will advance to a broader series of clinical trials to be run by Sanofi Pasteur, the vaccines division of the multinational pharmaceutical company Sanofi.
Zika infections reported in Florida as of Nov. 7
Number of cases
Total cases not involving pregnant women*
Cases involving pregnant women regardless of symptoms
* Counties of pregnant women not disclosed.
** Does not include local cases
Source: Florida Department of Health