New TB vaccine effective in half of the population in phase II trials

By Dr. Ananya Mandal, MDSep 26 2018

GlaxoSmithKline has come up with an experimental vaccine against tuberculosis (TB) that has shown effective prevention of the infection in half of the population it has been administered to.  This could be a breakthrough in preventing the killer disease say researchers since most of the recent vaccines developed against the disease have failed to show efficacy.

The presently used vaccine against TB is Bacille Calmette-Guérin (BCG) which was first developed in 1921 and is still being routinely administered to babies soon after birth in countries where TB still remains largely prevalent. The effectiveness of BCG however wears off after a few years and further it does not protect against the form of TB that affects the lungs and spreads via coughing and sneezing. This new vaccine however has shown efficacy in 54 percent of the adults who participated in the clinical trial and has stopped them from developing active TB. TB has gained importance as a public health problem in recent years and the United Nations has planned to hold a high level meeting on the disease this week (Wednesday 26th of September) in New York.

Secondary tuberculosis in lungs and close-up view of Mycobacterium tuberculosis bacteria, 3D illustration. Image Credit: Kateryna Kon / Shutterstock

This new vaccine from GSK is made to stop the latent or inactive form of TB from becoming active. TB has a latent course wherein it lies dormant or sleeping and nearly a quarter of the global population (1.7 billion people) live with latent TB infection. These individuals are all at a greater risk of contracting or getting active tuberculosis that may eventually prove to be fatal. According to estimates TB has killed 1.6 million people last year. This new vaccine named M72/AS01 developed by GSK in collaboration with Aeras, a nonprofit TB group backed by the Bill & Melinda Gates Foundation underwent rigorous animal studies followed by Phase I clinical trials. At present these results are from the Phase IIb trials of the vaccine have shown promise and the results are published in the latest issue of the New England Journal of Medicine.

The study took place in multiple centres in Kenya, Zambia and South Africa and 1786 adults were vaccinated twice during the study period. All participants were HIV negative and most of them had received BCG vaccine. A further 1787 adults were administered two placebo injections. Both groups were followed up for an average of 2.3 years and during this time 10 of the vaccinated individuals and 22 of the placebo treated individuals developed active TB of the lungs – pulmonary TB. Two in three individuals given the vaccine reported side effects such as reactions at the injection site and flu-like illness that lasted for a short duration.

According to the Areas Chief Executive Jacqui Shea this was “ground breaking” and the efficacy seen here is more than what has been seen before.

The difficulty with TB vaccines, explain the experts is that the bacteria tends to remain latent and there are no protective markers in blood that can tell the researchers if the vaccine is effective. Only absence of the active disease can prove the protective effects of the vaccine. This means that large clinical trials are needed to prove if the vaccine is effective.

GSK hopes better results would be seen in larger future trials and is working to refine the dosing schedules of the vaccines. The team of researchers are also working on specific target populations where the vaccines might show better efficacy. Emmanuel Hanon, GSK head of vaccines research, has said that there are additional improvements that could be brought about to improve efficacy.