Clinical trials underway for potential Zika vaccine at Walter Reed Army Institute of Research

The first in a string of five clinical trials to test a potential Zika virus vaccine is underway at Walter Reed Army Institute of Research. The trials will test the safety and efficacy of an "investigational" Zika vaccine called the Zika Purified Inactivated Virus, or ZPIV vaccine, in generating an immune system response to the virus that has had public health officials and the public alike on high alert for months now, the National Institutes of Health announced Monday.

Scientists with WRAIR, which is part of the U.S. Department of Defense, developed the vaccine. The National Institute of Allergy and Infectious Diseases, part of NIH, is co-funding the Phase 1 clinical trial with Walter Reed, serving as the regulatory sponsor as well as providing other support.

NIH explained the vaccine is based on the same technology used by Walter Reed seven years ago to successfully develop a vaccine for another flavivirus called Japanese encephalitis. Other flaviviruses include Zika, yellow fever virus, dengue virus, and West Nile virus.

[Also: Demand, backlog pose challenges for Zika testing in at-risk areas]

It contains whole but inactive Zika virus particles; this means the virus can't cause disease in humans. However, the protein shell of the inactivated virus remains intact such that the human immune system can recognize it and produce a response, the NIH said.

NIH also explained that during preclinical development of the vaccine, safety testing and non-human primate studies found the vaccine induced antibodies that neutralized the virus and protected the animals from disease when they were challenged with Zika virus.

"We urgently need a safe and effective vaccine to protect people from Zika virus infection as the virus continues to spread and cause serious public health consequences, particularly for pregnant women and their babies," said NIAID Director Anthony S. Fauci, M.D. "We are pleased to be part of the collaborative effort to advance this promising candidate vaccine into clinical trials."

[Also: Congress approves $1.1 billion in funding to help fight Zika]

WRAIR, NIAID and the Biomedical Advanced Research and Development Authority, part of the HHS Office of the Assistant Secretary for Preparedness and Response, have established a joint Research Collaboration Agreement to support the development of this vaccine.

The new study will involve 75 people ages 18 to 49 with no prior flavivirus infection who will be randomly divided into three groups of 25 people: the first group will receive two injections of the ZPIV test vaccine or a placebo (saline) 28 days apart; the other two groups will receive a two-dose regimen of a Japanese encephalitis virus vaccine or one dose of a yellow fever vaccine before beginning the two-dose ZPIV vaccine regimen.

"Investigators chose to administer additional flavivirus vaccines because U.S. service members are often vaccinated against these diseases before deploying to Zika-endemic areas," the NIH said.

A subgroup of 30 who receive the two-dose ZPIV regimen will receive a third dose one year later. All participants in the trial will receive the same ZPIV dose at each injection of 5 micrograms.

[Also: Zika researchers seek faster, easier detection test not requiring labratory]

NIH said the study will be monitored closely by several agencies, including the DOD, and an "independent physician not associated with the protocol" will monitor the conduct of the trial and report any safety issues.

The WRAIR study is expected to be completed by fall 2018. Four additional Phase 1 studies to evaluate the ZPIV investigational vaccine are also expected to launch in the coming months.

Twitter: @BethJSanborn