UM scientists develop single-dose cholera vaccine

September 26, 1992|By Liz Bowie | Liz Bowie,Staff Writer

Scientists at the University of Maryland School of Medicine have developed a vaccine for cholera that could help stop the spread of an epidemic sweeping several continents.

The genetically engineered vaccine, if it proves effective in final tests, also represents a breakthrough of another kind: it can be given orally in a single dose, making it practical for people in Third World countries where access to medical care is poor. Most vaccines require several doses and must be given by injection.

"There is no cholera vaccine that can be a tool for public health control, and yet we badly need such a vaccine," said Dr. Myron Levine, director of the center for vaccine development at the medical school. The university expects to license the vaccine to Swiss Serum and Vaccine Institute in Berne, Switzerland, the only company with the expertise and equipment to make the vaccine, according to Dr. Levine.

To develop the vaccine, researchers took live cholera bacteria and removed the gene that produces the proteins that make people ill. Whatremained was a bacteria that had the properties of cholera, but could not cause the illness.

Cholera, which causes nausea and severe diarrhea, can be easily treated if medical care is available. Even so, it has killed 5,802 people in the Western Hemisphere since January 1991, according to the World Health Organization. Another 672,000 people have been stricken by the disease but recovered.

Countries in Africa and Asia do not report cases to the World Health Organization, but cholera experts say it is epidemic in parts of Asia and could soon be in Africa as well.

Two studies, published earlier this week in the journal The Lancet and written by researchers at the University of Indonesia and the University of Maryland's medical school, showed the vaccine could protect people from cholera without side effects. The vaccine was tested on more than 3,000 people in the United States, Switzerland, Thailand, Peru, Chile and Costa Rica.

Larger scale tests of the vaccine are expected to begin in 1993 in Jakharta involving about 60,000 people. Dr. Levine said he hopes Europeancountries will license the vaccine's use for travelers by 1994 and that licensing in other countries would follow in 1995 or 1996.

University of Maryland researchers also believe they have developed another product for cholera as well: a quick, cheap test that detects cholera.

While a cholera test already exists, it takes at least 24 hours and sometimes several days to confirm the diagnosis, long enough for some patients to die.

The Smart Test, developed by the Maryland Biotechnology Institute and New Horizons Inc. in Columbia, could help doctors determine which patients need a more aggressive treatment, according to Rita Colwell, director of the institute, which is part of the University of Maryland system, and one of the researchers who developed the test.

"It is critical because if it is a severe case, you can die within hours," she said. In some countries where doctors see dozens of patients who have the same symptoms -- diarrhea and nausea -- they cannot afford to treat all people as though they have a life-threatening case, she said.

In addition, it could prove useful in testing water and food for traces of the bacteria that causes cholera, which is often spread in areas that don't have pure water and good sewage treatment, according to Lawrence J. Loomis, president of New Horizon, a privately owned company.

A similar test is being developed at the Johns Hopkins University School of Hygiene and Public Health, according to David Sack, associate professor of international health.

Besides a difference in the precision and sensitivity of the two tests, "Theirs will be faster, ours may be cheaper," he said.

Hopkins does not yet have a corporate partner to manufacture or sell the test.

Dr. Sack believes the Smart Test might eventually replace the conventional one.

However, he said, he doesn't believe it is accurate enough yet to test water or food.

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