Research Highlight

Revaccination may protect adults against TB

doi:10.1038/nindia.2020.11 Published online 22 January 2020

Administered at birth, Bacille Calmete-Guerin (BCG), the only approved vaccine against tuberculosis (TB), protects infants and children. However, it is less effective against pulmonary TB that affects young adults.

Researchers from the Indian Institute of Science in Bangalore, India show that revaccination with BCG may boost the immune system, reducing the risk of TB in adults1.     

About a quarter of the world’s population carries the TB-causing bacteria in their body. But, they show no symptoms of TB. Such people have a chance of developing TB in their lifetime. The researchers tried to see whether revaccination could protect them.  

The scientists, led by Annapurna Vyakarnam, selected 200 young adults from Madanapalle, a city in Andhra Pradesh, India which has high incidence of TB. All the adults had received a shot of BCG at birth. They were divided into two groups. One group had latent TB with no disease symptoms and the other didn’t carry any bacteria.  

Within each group, half of the individuals were revaccinated with BCG. Nine months after revaccination, their blood samples were analysed and then checked for the presence of specific immune cells against TB.

Compared to unvaccinated individuals, the revaccinated ones had higher number of specific immune cells. These cells produce cytokines, the signaling proteins that activate the immune responses against TB.

Revaccination, the researchers say, also boosted the numbers of specific immune cells that form the first line of defense against TB.


References

1. Rakshit, S. et al. BCG revaccination boosts adaptive polyfunctional Th1/Th17 and innate effectors in IGRA+ and IGRA– Indian adults. JCI. Insight. 4, e130540 (2019) doi: 10.1172/jci.insight.130540