BCG vaccine prevents TB in young children, but not adults - new study

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The Bacille Calmette-Guérin tuberculosis vaccine has been used for 100 years.
The Bacille Calmette-Guérin tuberculosis vaccine has been used for 100 years.
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  • A new study published in The Lancet found the Bacille Calmette-Guérin tuberculosis vaccine is efficient in children and not adults. 
  • The authors of the study suggest a booster shot after childhood.  
  • The vaccine has been used for 100 years. 

For 100 years, the Bacille Calmette-Guérin (BCG) vaccine has been used in tuberculosis (TB) prevention. 

Although the vaccine is given to at least 100 million people annually, researchers have always questioned its effectiveness. 

TB affects at least 10 million people a year across the world.

A new study, The Lancet Global Health, by Boston University School of Public Health researchers, found the BCG vaccination at birth provides significant protection against TB, but only among children under five years old. 

The study analysed data from the last 10 years from high-burden settings in 17 countries, including South Africa, China, Vietnam, Indonesia, Uganda, The Gambia and Brazil.

They analysed individual-level data from 26 longitudinal studies, which included nearly 70 000 participants exposed to TB from 1998 to 2018. The analysis examined variability across the studies, including the use of skin and blood TB infection tests, and accounted for potentially confounding factors, such as HIV, exposure status and history of prior TB. 

It found the overall effectiveness of BCG vaccination against all forms of tuberculosis was 18%. When stratified by age, BCG vaccination only significantly protected against all TB in children younger than five. 

READ | Covid-19, vaccinations led to new category of violations - SAHRC

Among the subset of 14 cohorts reporting specific forms of TB, researchers found evidence of a small, significant reduction in the rate of pulmonary TB with vaccination (19% effectiveness).

"For both of these outcomes, protection was concentrated in young children. Whether BCG vaccination protects young children from pulmonary tuberculosis is controversial and previous results have been heterogeneous,"  the paper states.

They also found protection from death among BCG-vaccinated children in the study. This persisted until participants were aged 14.

"Unlike many of the mRNA Covid-19 vaccines, which we know are highly effective, there is widespread debate on the BCG vaccine's effectiveness and duration of protection, as well as whether the vaccine only works in selective settings.

"Our findings indicate that BCG vaccination is effective at preventing tuberculosis in young children. Since tuberculosis in children is a highly debilitating and severe disease, BCG vaccination should continue to be used," said the study's lead author, Leonardo Martinez, an assistant professor of epidemiology.

The paper suggests that a booster shot be administered after childhood.

"Boosting immunoprotection is needed for older populations. Novel vaccines are urgently needed to supplement BCG vaccination in high-burden settings," Martinez said. 

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