Does BCG vaccination protect against infection with M. tuberculosis?

Area of Science:

• Immunology
• Infectious Diseases
• Public Health

Background:

• The efficacy of the bacille Calmette-Guérin (BCG) vaccine against Mycobacterium tuberculosis infection is debated.
• BCG vaccination at birth is a common practice, but its protective effect against tuberculosis (TB) infection requires further investigation.

Purpose of the Study:

• To examine the association between BCG vaccination and Mycobacterium tuberculosis infection prevalence in Vietnamese schoolchildren.
• To determine if a BCG scar correlates with a reduced prevalence of tuberculin skin test (TST) positivity.

Main Methods:

• Secondary analysis of tuberculin skin test (TST) survey data from Vietnamese schoolchildren (1988-2001).
• Assessed the association between the presence of a BCG scar and TST positivity.
• Adjusted for BCG-induced variations by analyzing different TST cut-off values.

Main Results:

• A positive association was observed between BCG scar and TST positivity.
• The strength of this association diminished as TST cut-off values increased.
• The association remained significant across different regions and survey years.

Conclusions:

• BCG vaccination at birth was not associated with a reduced prevalence of Mycobacterium tuberculosis infection in Vietnamese schoolchildren, as indicated by TST results.
• This finding contradicts results from a similar study in Tanzania.
• Potential explanations for the discrepancy include geographical differences and the prevalence of the Mycobacterium tuberculosis Beijing genotype, which may evade BCG-induced immunity.