BCG test reaction in previously BCG vaccinated children

Area of Science:

• Immunology
• Pediatric Infectious Diseases
• Public Health

Background:

• Bacillus Calmette-Guérin (BCG) vaccination is widely administered globally to prevent tuberculosis.
• Assessing the diagnostic accuracy of the BCG test in previously vaccinated children is crucial for tuberculosis management.
• Understanding immune responses post-BCG vaccination is essential for interpreting diagnostic tests.

Purpose of the Study:

• To evaluate the diagnostic utility of the BCG test in children under five years old who have previously received BCG vaccination.
• To determine the impact of prior BCG vaccination on BCG test reactions.

Main Methods:

• Studied BCG test reactions in 1095 non-tuberculous children aged 6 months to 5 years.
• All children included in the study had received BCG vaccination during the newborn period.
• Reactions were analyzed to assess diagnostic value in a vaccinated cohort.

Main Results:

• Previous BCG vaccination significantly influences BCG test reactions, typically causing an accelerated response.
• Even 4.5 to 5 years after vaccination, 51.4% of children demonstrated a strongly accelerated BCG test reaction.
• The degree of BCG test reaction diminishes over time but remains pronounced in a substantial proportion of children.

Conclusions:

• The BCG test is unreliable for diagnosing tuberculosis in children under five years of age with a history of BCG vaccination.
• Prior BCG vaccination interferes with the interpretation of BCG test results, limiting its diagnostic specificity.
• Alternative diagnostic methods for tuberculosis should be considered in BCG-vaccinated children.