TB Vaccine’s Failure Linked to Malnutrition in Third World

Malnutrition in underdeveloped nations may explain why tuberculosis vaccine often fails to protect residents of those countries, say researchers who have studied the disease in underfed guinea pigs.

“In Third World countries, the majority of the population is malnourished, especially in protein,” said Christine Tetzlaff, an immunologist at Texas A&M; University College of Medicine.

“We think this may serve as a good explanation for why the vaccine seems to be so ineffective in Third World populations,” she said.

A co-researcher, immunologist Rebecca Bartow, presented the findings at the annual meeting of the Federation of American Societies for Experimental Biology.

20 Million Cases

Tuberculosis, an airborne disease caused by bacteria, mainly damages the lungs. The World Health Organization estimates about 20 million active cases worldwide, with about 3 million deaths annually, mostly in the Third World.

While drugs can be used to treat the disease and even prevent infected people from becoming ill, Bartow said vaccination is the most cost-effective approach. But in 1983, World Health reported that the vaccine, which is injected under the skin, had little effect in protecting infants in a field trial started in 1968 in India’s Chingleput District.

The Texas A&M; study divided guinea pigs into two groups: those fed normal diets and those fed protein-deficient diets. Half the guinea pigs in each group were given the vaccine against tuberculosis, which is named BCG.

The vaccinations provided immunity to tuberculosis among the normal guinea pigs, but failed to do so among the protein-deficient animals. Further, when the malnourished guinea pigs were restored to a normal diet, the vaccine was effective, Bartow said.

She said the underfed guinea pigs also suffered impairment of white blood cells called T lymphocytes, which are vital parts of the disease-fighting immune system.