All children with severe measles should take vitamin A supplements to sharply reduce the risk of complications and death, a study published today concludes. Measles kills about 2 million children worldwide each year and leaves many more blind or afflicted with lung disease. The research conducted in South Africa found that the vitamin reduced the death rate by more than half and the duration of pneumonia, diarrhea and hospitalization by about one-third. The results ``indicate a remarkable protective effect of vitamin A in severe measles,'' the doctors wrote. Earlier research has turned up circumstantial evidence that the vitamin helps. As a result, the World Health Organization three years ago recommended that young measles victims take vitamin supplements anywhere that vitamin A deficiency is common or that more than 1 percent of measles cases are fatal. The study published in today's New England Journal of Medicine was conducted by Drs. Gregory D. Hussey and Max Klein of the University of Cape Town. The study randomly assigned 120 milligrams of vitamin A or identical-looking placeboes to 189 children who were hospitalized because of measles complicated by pneumonia, diarrhea or croup. Of the 12 children who died, 10 were taking placeboes. ``All children with severe measles should be given vitamin A supplements, whether or not they are thought to have a nutritional deficiency,'' the doctors wrote.