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A digitally-colorized transmission electron micrograph of Zika virus, which is a member of the family Flaviviridae. Virus particles, here colored blue, are 40 nanometers in diameter with an outer envelope and an inner dense core. Zika virus is spread to people through mosquito bites. The most common symptoms of Zika virus disease are fever, rash, joint pain and conjunctivitis, or red eyes. The illness is usually mild with symptoms lasting from several days to a week. Severe disease requiring hospitalization is uncommon. (Centers for Disease Control and Prevention photo by Cynthia Goldsmith)

A digitally-colorized transmission electron micrograph of Zika virus. Virus particles, in blue, are 40 nanometers in diameter with an outer envelope and an inner dense core. (Image courtesy of CDC/Cynthia Goldsmith)

The Walter Reed Army Institute of Research and the vaccines division of Sanofi Pasteur have agreed to co-develop a Zika virus vaccine based on initial work by WRAIR scientists and collaborators at Beth Israel Deaconess Medical Center in Boston.

According to a recent WRAIR press release, Army scientists and their collaborators are moving quickly to develop and test the vaccine candidate, which builds on a vaccine platform developed by WRAIR scientists for other flaviviruses, including Japanese encephalitis and dengue.

When this work is complete, the recently signed cooperative research and development agreement will allow the transfer of the Zika purified inactivated virus, or ZPIV, technology to Sanofi to explore advanced and larger-scale manufacturing and production.

The platform, said Army Col. Stephen Thomas, an infectious diseases physician, vaccinologist and the WRAIR Zika program lead, “has been proven to be safe, effective and able to meet regulatory requirements of the U.S. Food and Drug Administration.”

Vaccine is Feasible

As part of the agreement, WRAIR and collaborators will share data related to assays that measure antibody responses after vaccination with ZPIV, biologic samples generated during animal studies, and biologic samples generated during early human trials that assess ZPIV safety and immunogenicity, WRAIR officials said.

Preclinical work on the vaccine is being conducted with long-term HIV vaccine collaborators at the Beth Israel Deaconess Medical Center, a teaching affiliate of Harvard Medical School.

A preclinical study in mice, published June 28 in “Nature,” showed that a single dose of ZPIV generated an immune response that protected the mice against a Zika challenge with a Brazilian strain of the virus.

“The preclinical work gives us early confidence that development of a protective Zika virus vaccine for humans is feasible,” Army Col. Nelson Michael, the WRAIR Zika program co-lead, said.

Initial ZPIV supplies are being manufactured by the WRAIR’s Pilot Bioproduction Facility in Silver Spring, Maryland. The National Institute of Allergy and Infectious Diseases will provide regulatory sponsorship for the initial human trials, WRAIR officials said.

WRAIR researchers plan to start human testing at their Clinical Trials Center before the end of the year. At the same time, NIAID will begin more studies through its Vaccine Trials and Evaluation Units.

Growing Concern

According to the World Health Organization, as of June 29, 61 countries and territories have now reported continuing mosquito-borne transmission. Of these, 47 countries are experiencing a first outbreak of Zika virus since 2015, and 14 reported evidence of Zika virus transmission between 2007 and 2014, with ongoing transmission.

For the United States and its territories, during a press call this morning by public health experts and congressional leaders on the need for Zika funding, Centers for Disease Control and Prevention Director Dr. Tom Frieden said the more scientists learn about Zika the more concerned they are.

“It is now definitively confirmed that Zika does cause not only microcephaly but also other severe brain defects,” he said, and that it can cause such defects whether a person who is infected has symptoms or not.

In the continental United States, he added, travel-associated cases now stand at more than 1,130, including 320 pregnant women.

In U.S. territories the number of diagnosed and reported locally acquired cases stands at 2,526, including 279 pregnant women, Frieden said, noting that in Puerto Rico CDC is seeing “a rapid increase in the level of infection such that we think that each day dozens, and potentially as many as 50, more pregnant women [there] are becoming infected with Zika virus.”

At WRAIR, Thomas says infectious diseases have long been a threat to U.S. service members and that the military has extensive expertise and capabilities for developing countermeasures.

“The WRAIR has been studying flaviviruses for over 100 years,” he added, “since Walter Reed and his team discovered that yellow fever is transmitted by mosquitoes.”

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