[by:www.51voa.com] [00:00.00]The United States government has begun the first clinical testing [00:05.82]of an experimental vaccine designed to guard against Zika virus. [00:14.21]The National Institute of Allergy and Infectious Diseases [00:18.65]made the announcement earlier this week. [00:22.15]The experimental vaccine has already been tested in animals. [00:28.39]Anthony Fauci, the institute's director, said on Wednesday [00:33.12]that investigators should know soon whether the vaccine is safe for use in human beings. [00:41.61]He said the first human tests involve 40 human volunteers in the U.S. [00:50.49]"If we get a good immune response [00:53.08]and there are no safety red flags by the end of December 2016, [00:59.03]we should know if it's okay to move on to phase II." [01:04.23]He said the second phase could begin early next year. [01:10.26]Those trials will be larger studies, involving more volunteers. [01:16.74]They would be performed in countries where Zika has spread. [01:21.37]There, researchers would look not only at the safety of the experimental vaccine, [01:28.00]but its effectiveness in fighting infection. [01:32.91]Infected mosquitoes can pass the virus to people. [01:37.54]It can also be passed through sexual contact. [01:43.02]Zika usually causes minor problems in healthy people. [01:48.66]there is a real danger if an infected insect bites a pregnant woman. [01:56.45]The infection could spread to the fetus she is carrying. [02:01.88]If infected with the virus, women can give birth to babies [02:06.85]with a severe condition known as microcephaly. [02:11.81]The heads and brains of those babies are unusually small. [02:17.45]can cause many mental and physical problems and even death. [02:25.16]At first, the vaccine's main target will be women of the age when many women give birth. [02:33.39]Researchers would also be looking to prevent the disease in the general adult population. [02:41.14]The vaccine was developed with a relatively new technology. [02:47.47]It was scientifically engineered to contain a small piece of DNA from the virus. [02:56.01]DNA is short for deoxyribonucleic acid, which contains the biological commands for Zika. [03:07.24]The piece is so small that it is not infectious. [03:12.80]But it is big enough to produce a reaction from the body's natural defenses for fighting disease. [03:22.29]Fauci said the DNA method makes it easy to provide the vaccine quickly. [03:29.39]"We cannot afford to delay the development of a safe [03:34.41]and effective vaccine to prevent Zika virus infection," he added. [03:40.94]Zika infections have been reported in 50 countries and territories. [03:47.18]Most cases are in Central and South America and the Caribbean. [03:52.90]This week, U.S. officials announced that a number of people in the state of Florida have been infected. [04:01.78]They said all the infections resulted from infected mosquitoes. [04:08.68]I'm Anne Ball. [00:00.00]