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Zika Studies

The Walter Reed Army Institute of Research (WRAIR) has been studying infectious diseases including flaviviruses for more than 100 years. By leveraging its international research infrastructure and extensive infectious disease expertise, WRAIR was able to respond quickly to the Zika threat by developing a promising preventive vaccine.

Working in concert with government, industry and academic collaborators, WRAIR developed a Zika Purified Inactivated Virus (ZPIV) vaccine candidate. Researchers were able to move from initial conceptualizing of a Zika vaccine to publishing preclinical findings in two high impact publications within an unprecedented 180 days.

Institute researchers decided to move forward with the purified inactivated virus vaccine because it builds on a type of vaccine that has been licensed before. It is the same technology WRAIR used to develop its Japanese encephalitis vaccine, which was licensed in 2009.

This research is part of integrated, strategic U.S. Government effort to expedite vaccine development to protect people from the Zika virus. 

Promising Preclinical Findings

In June 2016 WRAIR and collaborators at Harvard University completed a promising preclinical study of the ZPIV vaccine, the findings of which were published in the journal Nature and demonstrated that single shots of the vaccine protected mice against subsequent Zika challenge.

Findings from another preclinical study in rhesus monkeys showed that the ZPIV candidate induced both binding and neutralizing antibodies in the two weeks after initial vaccination, which were substantially boosted following a second ZPIV dose given at week four. After being experimentally infected with Zika virus, vaccinated monkeys showed complete protection against both Brazilian and Puerto Rican strains of Zika virus as evidenced by no detectable virus in blood, urine and secretions after exposure. The study was published in the journal Science in August 2016.

Next Steps

WRAIR scientists moved rapidly to develop and test the ZPIV vaccine, and they began human testing at their clinic in Silver Spring in late 2016. Additional human trials are ongoing in the United States, supported by the National Institute of Allergy and Infectious Diseases (NIAID), through its Vaccine and Treatment Evaluation Units.

The vaccine technology must be further refined and developed for large scale manufacturing and testing. If the product is safe and looks promising in Phase I studies, it will move into Phase II testing. If warranted, a subsequent large Phase III efficacy study will determine if the vaccine is safe and effective at preventing Zika infection.

Foundation of Flavivirus Research

WRAIR has been researching flaviviruses, a family of viruses that includes yellow fever, Japanese encephalitis, dengue, West Nile and Zika viruses, for over a century, beginning in the 1890s when Major Walter Reed helped prove that yellow fever is spread by the Aedes aegypti mosquito.

A laboratory in Thailand has been conducting biosurveillance for Zika for the past three years, an effort that gave the Institute a head-start on vaccine development efforts. WRAIR also has in-house capabilities that have enabled them to quickly develop a vaccine candidate. The Pilot Bioproduction Facility headed by Dr. Kenneth H. Eckels produced small batches of vaccine candidates that were used for the preclinical studies and has manufactured a vaccine lot for use in initial (small) human clinical studies.