Progress continues to be made on creating a Zika vaccine, but taking any of the current candidates all the way through clinical trials and into production could take another few years, according to the latest information presented at a meeting of the Centers for Disease Control and Prevention’s Advisory Committee on Immunization Practices.
“As we all know, there is no vaccine for Zika, but there are a number of vaccines that have been developed over the last century or so for other flaviviruses, [such as] dengue, yellow fever, Japanese encephalitis, [West Nile], and we know a great deal about flaviviruses in general and the pathology that they have,” explained Gerald R. Kovacs, PhD, of the Biomedical Advanced Research and Development Authority (BARDA). “What we’re doing is using our lessons learned and working with the epidemiologists, with the clinicians, with the nonclinical development people, and using those lessons to develop new vaccines for Zika.”
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By next year, the second aim should begin to take shape, which will be the deployment of available vaccines under an appropriate regulatory mechanism to U.S. populations at high risk of exposure.
Finally, by 2020, Dr. Kovacs explained that the government hopes to be partnering with industry to commercialize a Zika vaccine and make it available for broad distribution.
The vaccines being looked at include an inactivated whole-virus vaccine, a live attenuated vaccine that utilizes flavichimeras, a recombinant vaccine, and nucleic acid vaccines, including DNA and mRNA varieties. While each have their pros and cons, only the inactivated whole-virus and live attenuated virus vaccines have licensed human flavivirus vaccines already available for protection against Japanese encephalitis, tick-borne encephalitis, yellow fever, and dengue.
The Zika Purified Inactivated Vaccine (ZPIV) has two candidates in “advanced development,” one by Sanofi Pasteur and the other by Takeda. Currently, the Walter Reed Army Institute of Research and the National Institute of Allergy and Infectious Diseases are conducting phase I clinical trials on both ZPIV candidates to determine their safety and immunogenicity profiles and gathering information on regimen, dosing, and prior flavi immunity. ZPIV has already proven to be fully protective in mice and nonhuman primates. Both the Sanofi and Takeda ZPIVs are expected to enter phase II testing by the middle of next year, and phase III testing at some point in 2019 or 2020.
“Human challenge was discussed at a consultation that the [National Institutes of Health] held a couple of months ago [and] in a nutshell, what the committee found was that there isn’t sufficient information right now on Zika relative to its pathology and how it’s transmitted from humans to humans to support a human clinical study at this time,” said Dr. Kovacs. “But they will, as we accrue more information about this disease, revisit the potential of doing this type of study.”
Dr. Kovacs also highlighted the need for manufacturers to stay in the game as long as possible, urging them not to be discouraged by dwindling interest and funding regarding the Zika vaccine initiative.
“We can develop as many vaccines as possible, but what’s necessary is for these manufacturers to stay in for the long haul,” he explained. “With cuts in funding and less and less enthusiasm for Zika, it becomes challenging for the U.S. government to continue to engage with manufacturers on these types of products [but] we hope that all of our partners will continue on their endeavors with us, but we can’t guarantee that.”
Dr. Kovacs disclosed that he is a consultant for BARDA within the Office of the Assistant Secretary for Preparedness and Response in the U.S. Department of Health & Human Services, and that he was speaking at the meeting on behalf of the organization.