# BCG vaccination at three different age groups: response and effectiveness

## TL;DR

This study shows that BCG vaccination at ages 6, 12, and 15 provides similar immune responses and effective TB protection during adolescence.

## Contribution

The study demonstrates that BCG vaccine effectiveness is consistent across different age groups during childhood.

## Key findings

- There was a strong correlation between tuberculin induration and scar formation after BCG vaccination.
- BCG vaccination significantly reduced TB incidence in the 14–24 age group compared to non-vaccinated peers.
- Post-vaccination immune responses did not differ significantly between the three age groups.

## Abstract

The protection, which some BCG vaccines could confer against the development of tuberculosis (TB) in childhood, might be indirectly reflected by the subsequent development of BCG immune response. The objectives of the study were to examine effectiveness and possible differences of post-vaccination reaction to a lyophilized BCG at different age groups and to evaluate its protection against TB in a decade's period.

We studied the post-vaccination PPD-skin reaction and scar formation at three different school levels, corresponding to ages of 6, 12 and 15 years old, vaccinated by a lyophilized BCG vaccine (Pasteur Institute), currently used in our country. During a 10-year follow up the reported TB cases in vaccinated and non-vaccinated adolescences up to 24-years old were analyzed and compared to the number of cumulative cases observed in the adult population of two neighboring territories (vaccinated and non-vaccinated).

There was a significant correlation (r2 = 0.87, p < 0.0001) between tuberculin induration and scar formation. There was no statistically significant difference between the three age groups (6, 12, and 15 year-old, respectively) in regard to the diameter of tuberculin induration or scar formation. Although 34% of 10-year later indurations were unpredictably related to the initial ones (increased or decreased), they were significantly correlated (r2 = 0.45, p = 0.009). The relative percentage of TB for the 14–24 years-age group to the adult studied population was significantly lower among the immunized children compared to the non-immunized population of the same age group (17/77, 22% vs. 71/101, 70%, p < .0001).

Our data suggest that the lyophilized BCG vaccine used for BCG programs at different age groups is equally effective and may confer satisfactory protection against tuberculosis in puberty.