DURBAN, South Africa – “Can we control tuberculosis without a vaccine?” asked Willem Hanekom, of the Bill &Melinda Gates Foundation, Saturday, and answered his own question: “No.”
But if the goal continues to be imperative, the approach is changing, he told an audience at the TB 2016. On Saturday Hanekom led his audience through a description of what he called a “massive shift in the last few years in TB vaccinology.”
He highlighted the strengths and limitations of the only existing vaccine against tuberculosis, Bacillus Calmette-Guerin, which offers infants and young children 80 percent protection against extra pulmonary tuberculosis, 50 percent protection against pulmonary TB and 20 percent protection against TB infection itself.
The first new approach is to act on the realization that “for real impact, we have to interrupt transmission,” he said.
That means vaccine developers and advocates must target adolescents and adults for vaccine development first, because they transmit tuberculosis — while infants and young children do not — and an effective vaccine for these groups would have an early impact on the TB epidemic. Ultimately, he noted, “preventing disease in adults will be more effective in preventing disease in children than vaccination.”
Other new ways of thinking about vaccine development include a focus on a vaccine that aims to prevent TB infection and the exploration of an aerosolized combination vaccination that would directly induce immunity in the lung.
He urged studying populations that never develop tuberculosis. That includes some miners who have been exposed to infection repeatedly. These individuals seem to develop antibodies differently from others who often go on to develop TB disease. Hanekom also suggested TB vaccine developers might consider a human challenge approach, used frequently in malaria vaccine research. It would involve infecting individuals with pulmonary tuberculosis to test the effectiveness of vaccine candidates. In any case, he pointed out the need, based on limited resources and other considerations to make decisions early about whether vaccine candidates are promising enough to go into human trials.
Although he enumerated numerous trials underway of TB vaccine candidates, several of which are in late stage trials, he was most excited about preclinical studies using cytomegalovirus to build a TB vaccine, based on studies in non-human primates that show a very strong immune response.
Will any of the current vaccine candidates prove effective? That is unclear, he said: “Modern efforts to develop a TB vaccine are just fifteen years old.”