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Federal health researchers have started testing an experimental Zika vaccine in people, officials announced Wednesday.

Dr. Anthony Fauci, director of the National Institute of Allergy and Infectious Diseases, said the first volunteer was given the vaccine candidate on Tuesday. The announcement comes a week after another experimental Zika vaccine made by Inovio Pharmaceuticals started being tested in people.

US health officials had previously said they hoped to start testing their vaccine in September, but they were able to expedite its development, showing how quickly scientists are trying to come up with tools to combat the virus.


The NIAID vaccine, which is known as a DNA vaccine, will be given to 80 healthy volunteers at sites in Maryland and Atlanta. The goal of this Phase 1 trial is to test its safety and to see what kind of immune response it can provoke. Some of the volunteers will be given two doses, while some will be given three.

Fauci said researchers hope to get initial results from the trial by the end of the year, and depending on the results, launch a Phase 2 trial in early 2017 in countries where Zika is endemic.


But Fauci warned that if Congress does not approve emergency funding for the fight against Zika, the Phase 2 trial could be delayed. The lack of funding, Fauci said, is “effectively impeding our smooth process on the vaccine front.”

With the DNA vaccine, a piece of genetic code is injected into the arm. The DNA produces proteins that can galvanize the immune system to identify and attack the virus if it tries to infect a person in the future.

DNA vaccines are a new focus in vaccine development, but none has been approved for use by US regulators so far. In some ways, they are easier to develop and could come with fewer risks than vaccines made from inactivated forms of the virus, Fauci said.

“It is a very convenient and easily scalable vaccine,” Fauci said in a call with reporters Wednesday.

The Zika virus, which is primarily spread by mosquitoes but can also be sexually transmitted, typically causes no symptoms or just a minor illness. But it can cause serious birth defects in fetuses if it infects pregnant women.

That means that women of childbearing age and their sexual partners are the target populations for a Zika vaccine, Fauci said.

The vaccine being developed by the federal health researchers is one of several candidates in the works.

The Inovio vaccine, which is also a DNA vaccine, is being given to 40 healthy adults in its Phase 1 trial.

A group of scientists has also shown a pair of other Zika vaccines — one made from DNA, one made from an inactivated form of the virus — can successfully protect mice from infection. The US Army developed the vaccine candidate made from the inactivated virus, and it has teamed up with the drugmaker Sanofi to advance the development of the vaccine.

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