BCG Might Protect Children From Initial TB Infection as Well as Active TB, Study Says

The BCG vaccine might protect children from initial tuberculosis infection as well as active TB disease, according to a study published in the Oct. 13 online issue of the Lancet, Reuters Health/Medscape reports. Previous research indicated that BCG was effective against active TB but not against initial TB infection. The effects of the vaccine have been difficult to gauge because the tuberculin skin test -- the method currently used to detect TB -- does not distinguish between whether a person has TB infection or simply has produced antibodies in response to the BCG vaccination. Ajit Lalvani, a clinical research fellow at the University of Oxford, and colleagues used a newly develop test that measures the response of CD4+ T cells to specific TB antigens to more accurately detect TB infection. The researchers tested 979 child household contacts of adult patients with active TB in Istanbul, Turkey, using both the old skin test and the new test. They found that 0.4% of the 770 vaccinated children had active TB, compared with 4.8% of the 209 unvaccinated children. They concluded that the BCG vaccine reduced by 92% the relative risk of developing active TB. In addition, the new test produced positive results for 416 children and the old skin test produced positive results for 497 children. Researchers said that the old test likely produced more positive results because it cannot distinguish between people with TB infection and those who have had the BCG vaccine. The researchers said that successful BCG vaccination programs might decrease the burden of latent TB infection and active TB in children. The study's findings also indicate that the new test could be used to gauge the efficacy of TB vaccine clinical trials, according to the researchers (Reuters Health/Medscape, 10/12).