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First Human Trial of Live, Attenuated Zika Vaccine Begins

Zika Virus Particles
Zika virus particles shown in African green monkey kidney cells. Credit: NIAID, modified.

Vaccinations have begun in a first-in-human trial of an experimental Zika virus vaccine, the National Institute of Allergy and Infectious Diseases (NIAID) announced today.

The experimental vaccine, known as rZIKV/D4Δ30-713, was developed in NIAID’s Laboratory of Viral Diseases. The vaccine uses a live, weakened dengue virus type 4 backbone that expresses Zika virus surface proteins. When injected, the attenuated virus should prompt an immune response. The Phase 1 clinical trial will analyze this response in participants and assess the safety of the experimental vaccine, which showed promise in earlier tests in rhesus macaques (monkeys).

The NIAID-sponsored trial will enroll a total of 28 healthy, non-pregnant adults ages 18 to 50 at the Johns Hopkins Bloomberg School of Public Health Center for Immunization Research in Baltimore, Maryland, and at the Vaccine Testing Center at the Larner College of Medicine at the University of Vermont in Burlington. Charles River Laboratories, in Malvern Pennsylvania, manufactured the vaccine candidate for the Phase 1 clinical trial.

Zika virus is primarily transmitted to humans by the bite of an infected mosquito or can be transmitted through sex. Although most people experience a mild illness or no symptoms when infected with Zika virus, babies born to women infected with Zika virus during pregnancy may have birth defects and/or develop health problems in their early years.

“Zika virus infection remains a significant threat to pregnant women and their developing fetuses, and we can expect to see periodic outbreaks and cases in areas where Aedes aegypti mosquitoes thrive,” said NIAID Director Anthony S. Fauci, M.D. No licensed vaccines for Zika virus infection are currently available; however, several are in various stages of development.

Dr. Whitehead also has developed a live, attenuated dengue vaccine candidate called TV003 designed to elicit antibodies against all four dengue virus serotypes. The experimental vaccine is currently under evaluation in a Phase 3 clinical trial conducted in Brazil by the Butantan Institute. Dr. Whitehead plans to develop a single vaccine that would protect against both Zika and dengue viruses.

After the vaccination, participants will receive a diary card to record their temperature at home at certain timepoints. During the following 6 months, they will return to the clinic periodically for physical examinations and to provide blood and other samples. Investigators will test the blood samples to see if participants are developing antibodies in response to the experimental vaccine.

Dr. Durbin expects that the trial will take up to one year to complete. For more information, visit and search identifier NCT03611946.

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