LOS ANGELES, CA (Catholic Online) - The experimental vaccine proved to be safe and effective against three of the four viruses that cause the disease. According to the World Health Organization, the number of dengue cases has increased significantly in recent years.

Dengue was introduced into the United States in 2009. According to the Florida Department of Health, 27 people living in Key West contracted the illness via locally acquired infections. There were 66 more residents in the area that contracted the illness the following year. The outbreak seems to have eased since then, however.

Appearing three days to two weeks after a mosquito bite, dengue symptoms can range from mild to incapacitating fever with severe headache, pain behind the eyes, muscle and joint pain and rash. When dengue occurs in children, symptoms include fever, abdominal pain, vomiting and bleeding.

"Nearly half a million people are thought to be hospitalized with dengue every year, the majority of which are children, so the development of a safe and effective vaccine has the potential to make a hugely positive impact," study co-author Dr. Derek Wallace of Sanofi Pasteur said in a journal news release.

Researchers in France and Thailand tested the effectiveness of the possible vaccine. Known as CYD-TDV, the vaccine was tested on more than 4,000 Thai children ranging in age from 4 to 11 years. Of the test subjects, 2,669 were given the vaccine, while the others received an inactive placebo.

The study proved that 2.8 percent of the children who received the vaccine were diagnosed with dengue, compared with 4.4 percent among the placebo group.

Secondary tests revealed the vaccine was effective in protecting against three of the viruses that cause dengue, DENV 1, 3 and 4. The virus DENV 2 was resistant to the vaccine. None of the children who received the vaccine suffered serious side effects.

Limited to Thailand, researchers say the tests confirm their findings in advance the development of a dengue vaccine.

"Our study constitutes the first-ever demonstration that a safe and effective dengue vaccine is possible," Wallace said. "Further trials of CYD-TDV are currently under way in a number of different countries, and our hope is that the positive results of this trial will be confirmed by these larger studies, taking place in a wide range of epidemiological settings."

© 2012, Catholic Online. Distributed by NEWS CONSORTIUM.