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Zika Vaccine Clinical Trial Underway

Testing Zika virus

Testing Zika virus in tissue cultures (Walter Reed Army Institute of Research)

7 November 2016. The first of a series of clinical trials testing inactivated Zika particles as a vaccine to protect against the live Zika virus is recruiting participants. The trial is conducted by Walter Reed Army Institute of Research in Silver Spring, Maryland, co-funded by National Institute of Allergy and Infectious Diseases, part of National Institutes of Health.

The Zika virus is transmitted primarily by aedes aegypti mosquitoes, the same species carrying chikungunya, dengue, and yellow fever pathogens. The virus may also be spread through sexual contacts. Most people contracting the Zika virus report symptoms such as mild fever, conjunctivitis or pink eye, and muscle and joint pain. The current Zika outbreak, however, is resulting in increasing numbers of cases of birth defects, notably microcephaly and Guillain-Barré syndrome.

Centers for Disease Control and Prevention reports as of 2 November 2016, more than 4,100 Zika cases in U.S. states and more than 30,000 cases in U.S. territories, with 1,005  pregnant women showing evidence of Zika infection in U.S. states and another 2,263 pregnant women with Zika infections in U.S. territories.  There are currently no treatments for Zika infections, nor is there a vaccine to prevent infections.

The Walter Reed Institute, part of Department of Defense, is developing the vaccine since DoD deploys service members to regions of the world where Zika is becoming endemic, or in parts of the U.S. where infections are reported. Also as of 2 November, 149 confirmed cases of Zika infection were reported in the military health system, including 4 pregnant service members and 1 pregnant family member.

The institute adapted a vaccine-development process it used in 2009 to create a vaccine protecting against Japanese encephalitis, transmitted with a virus in the same flavivirus family as Zika. That approach uses an inactivated virus, harmless to the recipient, yet still able to stimulate a response by the body’s immune system.

In this case, the vaccine contains whole, but inactive, Zika virus particles. Those particles include an intact protein shell, which is enough for the immune system to recognize it as an invader. Preclinical and safety studies show the inactive particles generated antibodies that neutralized two strains of live invading Zika viruses, protecting test rhesus monkeys from Zika infection.

The new clinical trial is testing the vaccine among 75 healthy adults with no previous Zika or other flavivirus infections. One-third of participants will be randomly assigned to receive two injections of the test vaccine or a placebo. Remaining participants will receive the test Zika vaccine after injection with either Japanese encephalitis or yellow fever vaccines, since service members are likely to receive vaccinations to protect against those diseases if assigned to regions where they occur. A sub-group of 30 individuals will also receive another dose of the vaccine one year later.

Four more test sites for the vaccine are expected to begin enrolling participants soon: Saint Louis University School of Medicine, Ponce Health Sciences University in Puerto Rico, NIAID’s Vaccine Research Center in Maryland, and Beth Israel Deaconess Medical Center in Boston. Those sites will test the vaccine with 48 to 90 adult participants in various dose levels and against a placebo.

Walter Reed Institute’s bioproduction facility is manufacturing the vaccine used in the early-stage trials. Biomedical Advanced Research and Development Authority, or BARDA, an office in the Department of Health and Human Services, is funding advanced development of a Zika vaccine candidate by drug maker Sanofi Pasteur. In September, Walter Reed Institute signed a six-year $43.2 million contract with Sanofi Pasteur, funded by BARDA, transferring the institutes technology to the company.

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