Treating latent tuberculosis normally requires nine months of daily pill-taking, but a new study shows that a far shorter course of medication, with once-a-week drugs, works just as well.

The study will greatly simplify the lives of about 300,000 Americans who undergo the treatment each year, and the new regimen may reduce the number of cases of active tuberculosis.

“This is the biggest breakthrough in the treatment of latent TB since the 1960s,” said Kevin Fenton, head of tuberculosis prevention at the Centers for Disease Control and Prevention.

Tuberculosis is caused by a slow-growing bacterium that usually infects the lungs. In most cases the body’s immune system controls the organism, so it doesn’t cause disease. Such “latent” cases can turn into organ-destroying infections, however, if a person’s immune defenses are weakened by AIDS, cancer, old age or poor nutrition.

Doctors advise preventive treatment for people exposed to someone with active tuberculosis and for those whose test results indicate a recent latent infection. For decades, that has meant taking a daily dose of the drug isoniazid for nine months.

The new study compared that regimen to a simpler one – a higher dose of isoniazid taken once a week, and another drug, rifapentine, also taken weekly, both for three months.

The study, of about 8,000 volunteers in the U.S., Canada, Brazil and Spain over three years, found seven cases of active TB among those taking the short course and 15 among those taking the traditional one.