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Zika vaccine induces robust immune responses in phase 3 trials 1

Dan Barouch, MD, PhD, is director of the Center for Virology and Vaccine Research at BIDMC and professor of medicine at Harvard Medical School.

Healthy adults presented strong immune responses after receiving an inactivated whole Zika virus vaccine under investigation, according to the interim analyzes of three Phase 1, placebo controlled, double-blind trials conducted at Beth Israel Deaconess Medical Center (BIDMC), Walter Reed Army Institute of Research (WRAIR), and Saint Louis University School of Medicine. The findings were published today in The Lancet.

"This is the first report on the immunogenicity of the purified Zika inactivated virus vaccine – or ZPIV – in humans," said co-principal Dan Barouch, MD, PhD, the director of the Center for Vaccine Virology and Research at BIDMC and professor of medicine at the Harvard Medical School. "Previously, we showed that ZPIV protected mice and monkeys against the Zika virus."

The ZPIV vaccine candidate was developed by WRAIR as part of the response of the US Department of Defense. UU At the 2015-2016 Zika outbreak in the Americas, and progress was made to a Phase 1 trial in November 2016. "The Zika epidemic underscored the need for the development of a safe and effective vaccine," Barouch said.

In the trials, a total of 67 healthy adult volunteers received two injections, four weeks apart: 55 received the ZPIV vaccine and 12 received a placebo. The researchers measured the immune responses of the participants by monitoring the levels of neutralizing antibodies to the Zika virus in the blood.

In almost all individuals immunized with the investigational vaccine, ZPIV produced neutralizing antibody responses two or four weeks after the last dose. On day 57, 92 percent of the vaccine recipients had strong antibody responses against the Zika virus, with levels of virus-neutralizing antibodies in the blood exceeding the protection thresholds observed in previous animal models.

When the researchers injected mice with antibodies from people vaccinated in the study, the animals were protected against subsequent exposure to Zika virus, unlike mice that were injected with antibodies from participants who received placebo. The researchers also noted that the vaccine was safe and only caused mild or moderate reactions.

"The Zika virus has the potential to be like other viruses that are dangerous in pregnancy, such as measles, mumps, or rubella, which were significantly killed by effective vaccines," said lead co-author Kathryn Stephenson, MD , MPH, director of the Clinical Trials Unit of the Virology and Vaccine Research Center of BIDMC and assistant professor of medicine at the Harvard Medical School. "These Phase 1 ZPIV studies are an important step in bringing an effective Zika vaccine to a successful conclusion. Unfortunately, we continue to need these studies because the threat of a resurgence of the Zika outbreak is very real."

The tests are continuous and differ in their design, with each one waiting to answer separate questions regarding the responses to ZPIV. The BIDMC trial is evaluating three different ZPIV dosing schedules, while the trial at Saint Louis University is evaluating the safety and immunogenicity of three different vaccine doses. The trial conducted at the WRAIR Clinical Trials Center in Silver Spring, Maryland, assesses the impact of pre-existing immunity against flaviviruses in volunteers who had been vaccinated against yellow fever or Japanese encephalitis, both viral cousins ​​of Zika, before receiving ZPIV .

The research team included researchers from a variety of institutions, including BIDMC, WRAIR, Saint Louis University School of Medicine, Saint Louis VA Medical Center, Henry M. Jackson Foundation for the Advancement of Military Medicine, the Emmes Corporation and the University of Vermont Medical Center and Larner College of Medicine.

This work was supported by the United States HIV Research Program through a cooperative agreement between the Henry M. Jackson Foundation for the Advancement of Military Medicine, Inc., and the Department of Defense. The work was also funded by the United States Defense Health Agency. This study was supported in part by the Contracts for Vaccine Testing of the Preclinical Services of the National Institute of Allergy and Infectious Diseases. The work was also funded in part by the Vaccine Management Evaluation Unit of the University of Saint Louis and supported by the Harvard Catalyst Clinical Research Center at BIDMC.

Source: Beth Israel Deaconess Medical Center

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