We may be closing in on a new, more effective vaccine for tuberculosis, according to a new paper published by members from GlaxoSmithKline’s Vaccine division.

Tuberculosis is a curable, chronic lung disease. Despite this, it remains one of the deadliest infectious diseases of this day and age. It caused an estimated 1.5 million deaths worldwide last year alone. It’s also one of the world’s leading causes of death, particularly in developing countries, the team explains.

The vaccine we currently use against tuberculosis (TB), the Bacille-Calmette-Guerin (BCG) vaccine, was licensed for human use way back in 1921 and has only been proven effective for limited forms of the disease in children under five. It doesn’t protect against the most common form of the disease in adults and teens (pulmonary TB).

However, a GlaxoSmithKline trial in three African nations showed the vaccine to have a 50% effectiveness three years after it was given to TB carriers that had not developed the disease.

An exciting first step

“These results demonstrate that for the first time in almost a century, the global community potentially has a new tool to help provide protection against TB,” GSK Vaccines’ chief medical officer Thomas Breuer said in a statement released at a conference on lung health in Hyderabad, India.

The South African Tuberculosis Vaccine Initiative trials (carried out in Kenya, South Africa, and Zambia) involved over 3,000 adult participants, the authors report. The initiative’s director Mark Hatherill said a vaccine would be “the only way in the short-term to interrupt TB transmission and get control of the epidemic”. If successful, the vaccine could prevent millions of new TB cases and subsequent deaths all over the globe.

Around 15 possible vaccines are in various stages of development around the world says Ann Ginsberg of the International AIDS Vaccine Initiative, which has been taking part in the research, but that the one GlaxoSmithKline has been working on is the most “exciting”.

The results are not conclusive yet: they still have to face longer trials with more participants in other countries to make sure they’re broadly-applicable. This process could take several years.

It’s estimated that one in four people worldwide carry latent TB (they’re carriers but don’t get sick and can’t transmit the disease). Between 5% and 15% of them will develop active TB, and people with compromised or weakened immune systems are more vulnerable.

India, the country where the announcement was made public, accounts for a quarter of the world’s TB cases. Indian Prime Minister Narendra Modi has set an ambitious target of ending the epidemic by 2025.

The paper “Final Analysis of a Trial of M72/AS01E Vaccine to Prevent Tuberculosis” has been published in the New England Journal of Medicine.