GUADALAJARA, Mexico – For all the emphasis on new tuberculosis treatments and repurposed drugs to meet the World Health Organization’s End TB goals at the Union World Conference on Lung Health, one elusive tool remains the missing piece in achieving the goal of eliminating TB: an effective vaccine that provides long-term protection. Without that, United Kingdom Parliamentarian Nick Herbert said here, elimination of TB is impossible.
The WHO End TB strategy, which aims to reduce TB deaths by 95 percent and cut new cases by 90 percent by 2035, assumes that a new TB vaccine will be available in the next two decades, said Johans Vekemans of the WHO.
“No new TB vaccine, no End TB,” he emphasized.
While 12 vaccine candidates are currently in the pipeline, of which two are being tested in China and India, researchers said a new vaccine is unlikely to be developed without more basic science research on tuberculosis immunology. One of the biggest barriers to vaccine development is that scientists have yet to identify correlates of protection – measurable signs that a person is protected from developing TB infection or disease. Without knowing those, Dereck Tait of Aeras said, scientists cannot know what kind of immune response a vaccine would need to stimulate in order to be effective.
“A big problem with vaccination studies is that the ultimate indication is prevention of TB disease,” he said. “But we don’t have correlates of protection, so we’ll go into very large studies with limited indications that the vaccine will be efficacious in humans.”
Inadequate funding is another barrier to TB vaccine development, Tait said. The Treatment Action Group has estimated that $445 million is needed every year for TB vaccine development. Only $80.7 million was available in 2015, however, leaving an annual funding gap of $364 million.
Researchers emphasized that 12 candidates in the pipeline is still progress. A decade ago only one was in development, and that was the first candidate to go into large clinical trials in half a century, Mike Frick of the Treatment Action Group said.
“We’re in an exciting juncture in TB vaccines at the moment,” Tait said. “We’ll see results from two trials in the first few months of 2018, another two in the latter part of the year, and results from a fifth trial in 2019.”