Does the BCG vaccine decrease the lifetime risk of tuberculosis?

Despite the vaccination numbers, there is still considerable debate about the effectiveness of the BCG vaccine in preventing tuberculosis and decreasing mortality, especially in older children and adults. To contribute in this regard, an international group of researchers sought to investigate the age-specific impact of BCG vaccination in children on development and mortality from pulmonary and extrapulmonary tuberculosis.

Read too: Genitourinary tuberculosis: what we need to know

BCG vaccine lowers lifetime risk of tuberculosis

The study

The authors carried out a systematic review, with meta-analysis of the individual data of the participants, of studies available in the databases. MEDLINE, Web of Science, BIOSISand basewithout language restrictions, published between January 1998 and April 2018. They searched for “case-contact” cohort studies on tuberculosis, using the terms “Mycobacterium tuberculosis”, “TB”, “tuberculosis”, and “contact” and excluding those for which information on BCG vaccination status was unavailable or those performed in countries that do not recommend BCG at birth. Authors of eligible studies were asked to provide individual participant data, such as characteristics of the “index patient”, contact (exposed patient) and environment.

The primary outcome was the diagnosis of tuberculosis in the contacts exposed to the disease and the secondary outcomes were the diagnosis of pulmonary and extrapulmonary tuberculosis and mortality. After adjusting for variables, the results were stratified by age and by infection status. Mycobacterium tuberculosis.


Of the 26 selected studies, carried out in 17 countries, a total of 68,552 participants were obtained. Of these, 1,782 (2.6%) developed tuberculosis — 1,309 (2.6%) among the 49,686 BCG vaccinated and 473 (2.5%) among the 18,866 unvaccinated.

The overall effectiveness of BCG against all types of tuberculosis was 18% (95% CI 0.74 – 0.91). When stratified by age, BCG vaccination only significantly protected children under five years of age against all types of tuberculosis (95% CI 0.49 – 0.81). Assessing only contacts with a positive tuberculin skin test, protection occurred for participants of all ages (95% CI 0.69 – 0.96), including those under 5 years of age (95% CI 0.47 – 0.97) and between 5 and 9 years (95% CI 0.38 – 0.99). There was no protective effect among those with negative tests, except in children under 5 years of age.

Evaluating the 14 cohort studies with information on whether the tuberculosis was pulmonary or extrapulmonary, BCG offered significant protection against pulmonary tuberculosis among all participants (95% CI 0.7 – 0.94), but not against extrapulmonary tuberculosis.

Another important finding, among the four studies with mortality data, was the significant protection of BCG against death (95% CI 0.13 – 0.49).

Know more: Tuberculous Pyomyositis (PT): learn about the extrapulmonary form of tuberculosis

practical message

These results demonstrate that BCG vaccination at birth is effective in preventing all types of tuberculosis and death in younger children (especially those under 5 years of age), but appears to be ineffective for these purposes in adolescents and adults. Thus, the study authors suggest considering boosters of tuberculosis immunization at other periods after childhood.

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