BALTIMORE — As Zika virus fears ramp up with the first U.S. cases of mosquito-borne transmission in Florida, researchers at the University of Maryland plan to begin testing a vaccine in humans before the end of the year.

The potential vaccine, which has shown promise in animal studies, is among the first to be in people as researchers race to curtail the virus blamed for a devastating birth effect that stunts brain development in newborns.

“A safe and effective vaccine to prevent Zika virus infection and the devastating birth defects it causes is a public health imperative,” said Dr. Anthony S. Fauci, director of the National Institute of Allergy and Infectious Diseases, in announcing that the University of Maryland School of Medicine’s Center for Vaccine Development would be one of three study sites for the vaccine.

Other sites for the study, which will involve dozens of healthy volunteers, are Emory University in Atlanta and the National Institutes of Health Clinical Center in Bethesda, Md.

“NIAID worked expeditiously to ready a vaccine candidate, and results in animal testing have been very encouraging,” Fauci said in a statement. “We are pleased that we are now able to proceed with this initial study in people. Although it will take some time before a vaccine against Zika is commercially available, the launch of this study is an important step forward.”

Researchers will look at the safety of the vaccine first and whether there is any immune response in this early test. If it is successful, other trials will be conducted in more affected countries.

One alternative vaccine, developed by Inovio Pharmaceuticals in Pennsylvania, already has been injected into its first human subject, that company announced last week. A vaccine based on a weakened version of the Zika virus, developed by Walter Reed Army Institute of Research in Silver Spring, Md., is scheduled to begin human testing in October. That vaccine candidate showed promise in a recent study in monkeys, according to research published Thursday in the journal Science.

While Zika is a mild infection for most people, the virus is now known to cause of microcephaly, which stunts the growth of babies’ heads and brains. The virus is spread by certain mosquitoes and through sexual contact.

With cases mounting in South and Central America, the World Health Organization declared Zika a public health emergency in February.