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Thailand claims world first with Dengue vaccine

posted 20 Mar 2011, 08:26 by Sam Mbale   [ updated 20 Mar 2011, 08:28 ]

Scientists in Thailand say they have developed the world's first vaccine for deadly Dengue fever, one of the world's most widespread and debilitating tropical diseases. According to the World Health Organisation, Dengue infects more than 50 million people each year.

Dengue fever is a tropical disease, spread to humans by infected female mosquitos. The World Health Organisation (WHO) says Dengue is on the rise. It says two fifths of the world's population is at risk of being infected. Against that statistic, the announcement of a viable prototype vaccine against the four distinct but related viruses that cause the disease is being regarded as a major development.

It has taken more than 30 years of research. The 

scientists from Thailand's Mahidol University, Chiang Mai University and the government's National Centre for Genetic Engineering and Biotechnology collaborated on the development of the vaccine. The researchers say the vaccine can block the Dengue virus strains DEN-1, DEN-2, DEN-3 and DEN-4 in one shot.Tests with monkeys, guinea pigs and mice showed the vaccine is safe and effective.

Dr. Sutee Yoksan, a director of the Center for Vaccine Development of Mahidol University, says that if clinical trial on humans prove just as effective, the vaccine could be made available for commerical use in about ten years.

"What we are trying to say is we have discovered the prototype vaccine. It means we can develop this vaccine for commercial use. We have done the test at a certain level with guinea pigs and the result shows good signs. For the next level, we have to inject the vaccine into humans. There are three stages to test a vaccine in humans - the first stage will take one year, the second stage will take two years, the third stage will take three years. To make the commercial vaccine, we need to pass those stages first, so it will take at least six years," said Sutee.

The WHO says incidents of Dengue fever have grown in recent decades to the point where it has become a major public health problem in tropical and sub-tropical regions around the world. Symptoms of Dengue are similar to those of flu, but vary according to the age of the patient. Fever, headaches, listlessness, muscle and joint pains are typical but severe cases can be fatal, with an estimated 22,000 people dying from Dengue each year. The disease is carried from person to person by infected mosquitos. Other mosquitos acquire the virus while feeding on the blood of an infected person.

The vaccine produced by Dr Sutee's team is a genetically engineered version of one of the Dengue viruses which produced a significantly weakened response from all four strains in the animal models. The greatest challenge, say the scientists, was overcoming the unique difficulties presented by DEN-3.

"The dengue virus types 1, 2, and 4 are quite similar in characters, like siblings. They are similar in functions but type 3 is a bit different. It has to be bred in a certain type of cell environment continuously, and given certain substances. When it can't be repeated, it's a fluke. But in this case, it can be replicated which means we have discovered something," said Sutee.

Sutee says it will be difficult for Thailand to produce the vaccine for commercial use as the country has no standardised laboratory capable of the task. Instead, the collaborators have entered into an agreement with BioNet Asia to develop the vaccine.

Sutee says the vaccine will be of great benefit in his own country, Thailand, where Dengue affected more than 113,000 people and killed 139 last year alone.