How long does a tuberculosis vaccination work?
For more than 100 years, there has been a single vaccination approved in the world for the prevention of tuberculosis. Vaccination with attenuated - but live - cow tuberculosis bacteria, Mycobacterium bovis Bacille Calmette Guérin, or "BCG" for short. The effectiveness of BCG vaccination in early childhood is undisputed. But how long does the efficacy last?
In the journal The Lancet Global Health, a team of researchers led by Leonardo Martinez of Boston University, Boston (USA), report the results of an extensive analysis involving 68,552 people who received BCG vaccination at birth, including 1782 people who developed tuberculosis. BCG vaccination protected children younger than 3 years against pulmonary tuberculosis and children younger than 5 years against all forms of tuberculosis but did not provide protection for adolescents or adults.
"The World Health Organization estimates that more than 85% of tuberculosis cases occur in adults," said Professor Lange of the Borstel Research Center, head of the Clinical Tuberculosis Unit at the German Center for Infection Research and one of the study's authors. "Only a new vaccine that also protects adolescents and adults against tuberculosis can decisively improve the prevention of tuberculosis." Currently, more than 10 candidate vaccines are in clinical trials. The most advanced is a modification of the BCG vaccine from Germany by the Max Planck Institute for Infection Biology in Berlin.
A significant finding of the current publication is also that BCG vaccination is consistently and highly protective against death in general up to the age of 14 years. It is assumed that the effect of "trained immunity" is responsible for this. According to this theory, vaccination in infancy with a live vaccine, results in nonspecific, functional reprogramming of innate immune cells and nontargeted protection against other pathogens. Epidemiologic studies in high-incidence countries of tuberculosis show a significant reduction in infant mortality in BCG-vaccinated infants. This is also independent of tuberculosis. It is particularly interesting that this effect can apparently also be transferred from BCG-vaccinated mothers to the infants.
Martinez L et al. Infant BCG vaccination and risk of pulmonary and extrapulmonary tuberculosis throughout the life course: a systematic review and individual participant data meta-analysis Lancet Glob Health 2022; 10: e1307–16 DOI: https://doi.org/10.1016/S2214-109X(22)00283-2