New research has found that the so-called BCG vaccine can protect some children against tuberculosis infection and the development of the disease. A study published in the latest issue of the British medical journal, The Lancet, says the finding presents researchers with another avenue in the search for an effective vaccine against the lung disease.

For the past 100 years, children around the world have been administered the BCG vaccine to keep them from acquiring tuberculosis from a sick relative. But the drug has proved to be only partially effective in children, and is ineffective in protecting adults against the most serious form of the disease, pulmonary tuberculosis.

To become sick, a person must first become infected with the TB bacteria, which may never convert to active disease. Worldwide, an estimated two billion people are infected with the tuberculosis organism, about 10 million people become sick every year.

Researchers at Oxford University studied the limited effectiveness of the BCG vaccine, but were surprised by one of their findings.

Ajit Lalvani led the team of scientists.

"What we have shown is that, although it is of limited effectiveness in preventing disease, the vaccine has properties that were not recognized until now," said Ajit Lalvani. "And that it can actually enhance the body's ability to protect itself against acquiring infection in the first place."

Since many of those who are infected never develop active TB, Dr. Lalvani says, the prevailing view by scientists is that BCG somehow keeps the tuberculosis bacteria in check for a time.

Immunologist Stephen Kauffman of the Max Planck Institute in Berlin, Germany, is working to enhance the effectiveness of the BCG vaccine.

"BCG can control the bacteria to a certain level, but it cannot eradicate them," said Stephen Kauffman. "But even those young children who are protected at early ages, still can develop TB."

British researchers developed a sensitive blood test to determine whether someone had an inactive form of tuberculosis. Then, they studied almost 1,000 Turkish children up to age 16, who lived with a relative with active pulmonary tuberculosis.

About 80 percent of the children were known to have been vaccinated with BCG. Investigators found that the inoculated children were significantly less likely to be infected with TB bacteria than children who had not been vaccinated with BCG.

As one indication, TB-exposed children who had a scar from a BCG vaccination had a 24-percent reduction in their risk of infection. Again, Dr. Lalvani.

"It had not been known that BCG vaccine could have that effect," he said. "That had never been known. And, indeed, there is no factor known to date that we know of, which actually protects people against TB infection. This is the first time that has been possible to identify such a factor."

The efforts of scientists like Dr. Kauffman have focused on reformulating BCG, so it heightens the body's immune response against tuberculosis.