BCG TB vaccine may be more effective than previously thought

The Bacille Calmette Guérin vaccine against tuberculosis may be more effective against the most common form of the disease than previously thought, according to a study recently published in Clinical Infectious Diseases.

The BCG vaccine is included in many countries' childhood vaccination programs and it is the only licensed TB vaccine. It was previously thought to only be effective against the less common forms of TB that occur away from the lungs. Its effectiveness against pulmonary TB, which is found in the lungs and causes the greatest TB burden, varied widely depending on location.

Researchers with the London School of Hygiene & Tropical Medicine conducted a review of global literature on all reported BCG trials and found the vaccine is actually highly protective against pulmonary TB in all parts of the world. The researchers found the reason for the apparent variation in protection was due to prior infection, which reduced the efficacy of the vaccine.

"This research corrects a longstanding misconception that BCG is ineffective against pulmonary disease, and confirms its importance in controlling the major burden from TB and main source of transmission in all settings," Punam Mangtani, the lead author of the study, said. "Now that we know previous infection can lower the protection provided by the vaccine, it is important that BCG is given as early as possible in a person's life, and ideally immediately after birth."

The study found that BCG vaccination for individuals with no prior history of TB infections, including young infants, demonstrated a much higher efficacy against pulmonary TB. The research suggests that any new TB vaccine based on BCG would need to be administered prior to infection.