As world leaders pledged support for the fight against tuberculosis at the United Nations this week, some good news in the effort to develop weapons to combat the bacterium nearly slipped under the radar.
An experimental TB vaccine showed solid protection in a clinical trial reported Tuesday in the New England Journal of Medicine. The vaccine is being developed by GSK and Aeras, a nonprofit organization working on affordable tuberculosis vaccines.
The vaccine was tested in volunteers with latent tuberculosis — in other words, people who had been infected, but who did not at the time of vaccination have active TB disease. People who received placebo vaccine progressed from latent to active disease at roughly twice the rate of people in the trial who received the active vaccine.
The vaccine, which is known by the working name M72/AS01, was deemed to offer 54 percent protection based on the trial, conducted in Kenya, South Africa, and Zambia.
If this were a new mumps vaccine, that figure would lead to the shelving of the project. But given the enormous number of people around the globe who are infected with TB — the World Health Organization estimates that a quarter of the world’s population has latent TB — these results are being met with a lot of excitement.
“Since we do not have any vaccines that can decrease the transition from TB latency to active TB disease, a vaccine with a 54 percent efficacy signal is impressive and an important advance,” said Dr. Anthony Fauci, director of the National Institute for Allergy and Infectious Diseases.
“We obviously want to improve on this and optimize the efficacy to greater than 54 percent; however, this is in and of itself an important advance in TB research,” said Fauci, who was not involved in the research.
There is an existing TB vaccine, called bacilli Calmette-Guérin, or BCG. But studies have shown conflicting results about its effectiveness; it is not generally used in the United States.
People who contract tuberculosis have a 5 percent to 15 percent lifetime risk that their latent infection will progress to active disease. The WHO estimates that in 2017, 10 million people became ill with TB and 1.6 million people died from the disease.
Latent tuberculosis can be treated with drugs. But the regimens — nine months of daily treatment with the antibiotic isoniazid or four months with another antibiotic, rifampin — are cumbersome. Inevitably a treatment that requires months of daily medications is one that some portion of people will stop taking.
Dr. Dick Menzies, who recently published landmark studies showing that the four-month course of rifampin was as effective as nine months of isoniazid, was enthused about the data on the TB vaccine.
Rifampin might be a bit more effective than the vaccine, but the fact that vaccine is a one-and-done treatment that will likely cost the health system less means the vaccine might be used by low- and middle-income countries, he said.
Menzies, a respirologist and professor of medicine at Montreal’s McGill University, called the study findings “a big step forward.” Menzies was not involved in the research.
An editorial on the study published in the journal suggested the findings — which come from a Phase 2b, or intermediate stage, clinical trial — could be the foundation for further research.
Dr. Barry Bloom, a former dean of Harvard T.H. Chan School of Public Health, called the findings a proof of principle. He suggested it would be worth exploring whether the vaccine could be tweaked to improve on the efficacy.
Additional studies will also be needed to determine how long protection from the vaccine lasts, Bloom said, as vaccinated people might need to have booster shots later.
GSK and Aeras said study of the vaccine continues. But they celebrated these findings.
“Given the overwhelming public health need, the importance of these promising results, which need to be confirmed through additional clinical research, cannot be overstated, said Jacqui Shea, chief executive officer of Aeras. “An effective vaccine, able to reduce transmission, would be by far the most impactful new intervention to end the global tuberculosis epidemic.”