"If it's a home run, we'll know pretty quickly," Fauci said, adding that if it is successful, phase 2 trials could begin as early as January.
Human trials of another DNA-based vaccine created by Inovio Pharmaceuticals
started in Miami a few days ago, but Fauci stressed that those DNA inserts are different from the ones the his agency is using.
"This vaccine includes a small piece of DNA with genes that code for Zika-virus proteins," Fauci said. It's injected via a coil spring injector into the deltoid muscle of the arm, where the body's cells read the DNA and create virus-like particles that should activate the immune system to create antibodies.
A total of 80 volunteers ages 18 to 35 will receive the vaccine by the end of August at three study sites in Bethesda, Maryland, Baltimore and Atlanta. The volunteers will be broken into three groups that will receive the same dose at different intervals over a 20-week period.
After the first injection, volunteers will be required to return for follow-up visits over a 44-week period to monitor their health.
The agency stressed the safety of the vaccine, noting that "DNA vaccines do not contain infectious material -- so they cannot cause a vaccinated individual to become infected with Zika -- and have been shown to be safe in previous clinical trials for other diseases."
If preliminary results show effectiveness, Fauci said, the National Institute of Allergy and Infectious Diseases has enough doses of the vaccine on hand to move from phase 1 to phase 2 trials. However, it does not have enough money to plan and administer the phase 2 study, he said, adding that Congress needs to act on the Obama administration's request for additional funding to fight Zika.
That sentiment was echoed today by White House press secretary Josh Earnest: "If Republicans continue to obstruct funding for the Zika virus, then that's going to limit our ability to rapidly develop the kind of vaccine that, next summer or the summer after that, could start protecting the American people from the Zika virus and limit the risk associated with this particular disease."
If phase 2 happens as planned, Fauci said, he thought the earliest the vaccine might be used would be in early 2017, with FDA approval.
"The target of the vaccine will be women of childbearing age and their sexual partners," he said, "to protect their unborn children from birth defects."
Zika has been shown to be responsible for an alarming increase in microcephaly, in which babies are born with small brains and heads, as well as other hearing, vision and developmental disorders.
Because it's well-known that Zika does the most damage in the first trimester of a pregnancy, Fauci stressed that vaccinating girls before they reach puberty in areas hard-hit by Zika is the ultimate goal.
"In the real world, women are most vulnerable before they even know they are pregnant," he said. "So we need to vaccinate as young as we can possibly get them."