NEW YORK, USA – An experimental vaccine could potentially prevent tuberculosis from developing in adults, marking a milestone in finding new ways to prevent an old disease, researchers said Tuesday, September 25.

The vaccine, developed by pharmaceutical giant GlaxoSmithKline in partnership with nonprofit TB group Aeras, is designed to protect people already infected by the TB bacteria (also called latent TB) but are not yet sick of it.

After a mean follow up of 2.3 years, 10 of the 1,786 adults given two doses of the vaccine one month apart developed active pulmonary TB compared to 22 of the 1,787 given two placebo injections. Clinical trials were conducted in Kenya, Zambia, and South Africa in 11 different sites.

The results of the midstage clinical trial of the vaccine, known as M72/AS01, were published online by the New England Journal of Medicine.

“Those who got the vaccine had about half as much TB disease develop over the first couple years over those who got placebo. So the efficacy of the vaccine was shown as 54% in this population,” said Ann Ginsberg, chief medical officer of Aeras.

The 54% efficacy rate achieved in the midstage clinical trial is low compared to immunizations for other diseases, but experts remained optimistic that the findings represented a scientific breakthrough in preventing adults with latent TB from developing active pulmonary TB.

“These initial findings represent a significant innovation in the development of a new and much-needed vaccine and advance the scientific understanding of tuberculosis,” Emmanuel Hanon, GSK senior vice president and head of research and development, said in a statement.

The announcement of the test results came at the same time as the United Nations High-Level Meeting on TB happening Wednesday, September 26.

It is the first time for the UN to convene a high-level meeting on TB to call on global leaders around the world to make political commitments and necessary investments for a coordinated global TB response to end the epidemic.

An estimated $1.25 billion is needed to fund the development of a vaccine to prevent TB and control the spread of drug-resistant strains.

Highest infectious disease killer

Tuberculosis, a bacterial infection that mainly attacks the lungs, is the world’s highest infectious disease killer.

An estimated 4,500 people die from TB every day. TB killed 1.6 million people in 2017 and infected 10 million others.

The latest global estimates showed that an estimated 1.7 billion people have latent TB infection, making them vulnerable to developing active TB.

Worldwide, TB incidence rate is falling at about 2% per year, but according to health experts, infection rates need to fall by 4% to 5% percent per year to reach the 2020 milestone in the End TB Strategy.

The development of the vaccine is seen by health experts as a crucial step in ending the epidemic and controlling the emerging public health crisis of drug-resistant TB. 

In 2017, more than half a million people developed resistance to rifampicin, the most effective first line drug against TB.

Currently, the only vaccine against TB is Bacille Calmette-Guérin (BCG), which was developed in 1921. It is routinely administered to babies in countries with high rates of TB to prevent severe disease. However, BCG does not protect adults and adolescents from developing TB.

While the encouraging results of the M72/AS01 vaccine represented a “landmark moment,” there is still much work to be done, such as testing in a larger number of people.

“This is still an investigational vaccine candidate which means that we now have proof of concept that works. This is the first vaccine that has shown this level of efficacy. And the first ever vaccine [that has] shown that you can protect people infected by the bacteria but are not yet sick of it,” said Ginsberg. – Rappler.com

Ana P. Santos is currently in New York covering the UN High-Level Meeting on Tuberculosis with support from the Stop TB partnership.