The University of Maryland School of Medicine in Baltimore began testing Zika vaccinations last week, continuing a project to develop a vaccine for the disease, said Kathleen Neuzil, a professor in the medical school and director of the school's Center for Vaccine Development.

On Sept. 13, 18 vaccinations were administered to healthy volunteers at the school. About 12 more will be administered next week, said Monica McArthur, the principle investigator of the project and a professor at the school.

The National Institutes of Health Clinical Center in Bethesda is collaborating with the school and Emory University for this project, McArthur said. The NIH developed the vaccine, and researchers at the three locations will test it on volunteers and gather data.

Neuzil said tests are going well so far.

"To vaccinate 18 people in one day is a large number," she said. "It shows people were very interested in this vaccine and in this study."

The vaccine uses DNA, not a live virus, to "trick the body into thinking that it's seeing the virus when it's not," McArthur said.

Because there is no live virus present in the vaccine, it does not expose volunteers to Zika and cannot infect participants, McArthur said.

"There are so many manifestations with [Zika]," said Kirsten Lyke, a professor at the medical school who is working on the vaccination. "The most disturbing is the high instance of neurologic defects in fetuses."

Typically the virus causes no more than a rash and fever, Lyke said, but more rarely it can cause neurological issues.

"It's just the tip of the iceberg at this point," Lyke added.

Pregnant women are most at risk because the virus can cause neurological defects in fetuses, Lyke said, but Zika can also cause deafness, blindness and Guillain-Barré Syndrome, a neurological disorder that can cause muscle weakness or paralysis, according to the Centers for Disease Control and Prevention.

There are several advantages to this type of vaccination, McArthur said, including safety for those with immunodeficiencies because volunteers can't  contract the virus from it. A DNA vaccine was also successfully developed for a similar disease, West Nile Virus, "and was shown to be safe and induce good immune responses," McArthur said.

As part of this phase, volunteers will receive either two or three doses of the vaccine over several days and return for blood tests periodically, Neuzil said. The entire phase will take about 44 weeks, she said.

"What we hope is first of all to make sure the vaccine is safe and well tolerated," Neuzil said.

Researchers also hope to see the vaccine stimulate an immune response against the virus, she added.

In the United States, Florida is the only state where Zika has spread by mosquito, Lyke said, but within the next few years it is expected to continue spreading. In several states including Florida, however, the virus has spread by other means, such as sexual transmission.

Maryland has not had any infections from the insect, "but we have reason to believe we have the mosquitoes that could carry Zika," Lyke said.

McArthur said the vaccination project is important because of "the major public health threat that Zika poses to the global community."

"Identifying a safe and effective vaccine as quickly as possible is critical to protect the public at large," she said.

CORRECTION: Due to a reporting error, a previous version of this story incorrectly stated that the National Institutes of Health Clinical Center in Bethesda is collaborating with the University of Maryland and Emory University for Zika vaccinations. It is collaborating with the University of Maryland School of Medicine in Baltimore and Emory. This story has been updated.