The tuberculosis vaccine known as BCG (for Bacillus Calmette–Guérin) has been used for years, especially in developing countries, to prevent TB. Now a new study indicates that the BCG vaccine may actually protect against TB infection and disease.
According to the Centers for Disease Control and Prevention, TB is a serious disease, because:
- One third of the world’s population is infected with TB.
- In 2012, nearly nine million people around the world became sick with TB disease. There were about 1.3 million TB-related deaths worldwide.
- TB is a leading killer of people who are HIV-infected.
The BCG vaccine has undergone many studies, with results indicating it is 60 to 80 percent effective against TB in children. It has been unclear, however, if the vaccine works against actual TB infection, according to materials provided by the British Medical Journal, which published the study.
Researchers analyzed data from 1950 to 2013 on vaccinated and unvaccinated children who were younger than 16 and who had known recent exposure to patients with pulmonary TB. The children were screened with standard TB tests to check for the disease. There were 14 studies and 3,855 participants.
Children in the analysis were part of a TB outbreak investigation of children screened for TB because they were close contacts of people diagnosed with TB,. Participants lived in the United Kingdom as well as countries such as Spain, Greece, Indonesia, and South Africa.
The BCG vaccine was 19 percent effective against TB among vaccinated children who had been exposed to TB compared to children who were not vaccinated. When they restricted their analysis to six studies of 1,745 children in whom there was information on progression to active TB at the time of screening, there was a 27 percent protection against infection and a 71 percent protection against active TB.
In children who were actually infected with TB, the protection from vaccination against the infection was 58 percent.
“Our results support a paradigm shift in the understanding of how antimycobacterial vaccines (new and old) can work, from the view that BCG protects against disease but not against infection to one that it protects against infection itself,” the authors conclude.